Merge branch 'master' into python-tests

40 files changed, 1470 insertions, 502 deletions

diff --git a/guix/build-system/dub.scm b/guix/build-system/dub.scm
new file mode 100644
index 0000000000..13c89e8648
--- /dev/null
+++ b/guix/build-system/dub.scm
@@ -0,0 +1,147 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013 Andreas Enge <andreas@enge.fr>
+;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
+;;; Copyright © 2016 David Craven <david@craven.ch>
+;;; Copyright © 2016 Danny Milosavljevic <dannym@scratchpost.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix build-system dub)
+  #:use-module (guix search-paths)
+  #:use-module (guix store)
+  #:use-module (guix utils)
+  #:use-module (guix derivations)
+  #:use-module (guix packages)
+  #:use-module (guix build-system)
+  #:use-module (guix build-system gnu)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-26)
+  #:export (dub-build-system))
+
+(define (default-ldc)
+  "Return the default ldc package."
+  ;; Lazily resolve the binding to avoid a circular dependency.
+  (let ((ldc (resolve-interface '(gnu packages ldc))))
+    (module-ref ldc 'ldc)))
+
+(define (default-dub)
+  "Return the default dub package."
+  ;; Lazily resolve the binding to avoid a circular dependency.
+  (let ((ldc (resolve-interface '(gnu packages ldc))))
+    (module-ref ldc 'dub)))
+
+(define (default-pkg-config)
+  "Return the default pkg-config package."
+  ;; Lazily resolve the binding to avoid a circular dependency.
+  (let ((pkg-config (resolve-interface '(gnu packages pkg-config))))
+    (module-ref pkg-config 'pkg-config)))
+
+(define %dub-build-system-modules
+  ;; Build-side modules imported by default.
+  `((guix build dub-build-system)
+    (guix build syscalls)
+    ,@%gnu-build-system-modules))
+
+(define* (dub-build store name inputs
+                      #:key
+                      (tests? #t)
+                      (test-target #f)
+                      (dub-build-flags ''())
+                      (phases '(@ (guix build dub-build-system)
+                                  %standard-phases))
+                      (outputs '("out"))
+                      (search-paths '())
+                      (system (%current-system))
+                      (guile #f)
+                      (imported-modules %dub-build-system-modules)
+                      (modules '((guix build dub-build-system)
+                                 (guix build utils))))
+  "Build SOURCE using DUB, and with INPUTS."
+  (define builder
+    `(begin
+       (use-modules ,@modules)
+       (dub-build #:name ,name
+                    #:source ,(match (assoc-ref inputs "source")
+                                (((? derivation? source))
+                                 (derivation->output-path source))
+                                ((source)
+                                 source)
+                                (source
+                                 source))
+                    #:system ,system
+                    #:test-target ,test-target
+                    #:dub-build-flags ,dub-build-flags
+                    #:tests? ,tests?
+                    #:phases ,phases
+                    #:outputs %outputs
+                    #:search-paths ',(map search-path-specification->sexp
+                                          search-paths)
+                    #:inputs %build-inputs)))
+
+  (define guile-for-build
+    (match guile
+      ((? package?)
+       (package-derivation store guile system #:graft? #f))
+      (#f                                         ; the default
+       (let* ((distro (resolve-interface '(gnu packages commencement)))
+              (guile  (module-ref distro 'guile-final)))
+         (package-derivation store guile system #:graft? #f)))))
+
+  (build-expression->derivation store name builder
+                                #:inputs inputs
+                                #:system system
+                                #:modules imported-modules
+                                #:outputs outputs
+                                #:guile-for-build guile-for-build))
+
+(define* (lower name
+                #:key source inputs native-inputs outputs system target
+                (ldc (default-ldc))
+                (dub (default-dub))
+                (pkg-config (default-pkg-config))
+                #:allow-other-keys
+                #:rest arguments)
+  "Return a bag for NAME."
+
+  (define private-keywords
+    '(#:source #:target #:ldc #:dub #:pkg-config #:inputs #:native-inputs #:outputs))
+
+  (and (not target) ;; TODO: support cross-compilation
+       (bag
+         (name name)
+         (system system)
+         (target target)
+         (host-inputs `(,@(if source
+                              `(("source" ,source))
+                              '())
+                        ,@inputs
+
+                        ;; Keep the standard inputs of 'gnu-build-system'
+                        ,@(standard-packages)))
+         (build-inputs `(("ldc" ,ldc)
+                         ("dub" ,dub)
+                         ,@native-inputs))
+         (outputs outputs)
+         (build dub-build)
+         (arguments (strip-keyword-arguments private-keywords arguments)))))
+
+(define dub-build-system
+  (build-system
+    (name 'dub)
+    (description
+     "DUB build system, to build D packages")
+    (lower lower)))
diff --git a/guix/build-system/gnu.scm b/guix/build-system/gnu.scm
index f6df183da4..730e638c89 100644
--- a/guix/build-system/gnu.scm
+++ b/guix/build-system/gnu.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -19,7 +19,7 @@
 (define-module (guix build-system gnu)
   #:use-module (guix store)
   #:use-module (guix utils)
-  #:use-module (guix combinators)
+  #:use-module (guix memoization)
   #:use-module (guix derivations)
   #:use-module (guix search-paths)
   #:use-module (guix build-system)
@@ -84,15 +84,15 @@ builder, or the distro's final Guile when GUILE is #f."
 
   (let loop ((p p))
     (define rewritten-input
-      (memoize
-       (match-lambda
-        ((name (? package? p) sub-drv ...)
-         ;; XXX: Check whether P's build system knows #:implicit-inputs, for
-         ;; things like `cross-pkg-config'.
-         (if (eq? (package-build-system p) gnu-build-system)
-             (cons* name (loop p) sub-drv)
-             (cons* name p sub-drv)))
-        (x x))))
+      (mlambda (input)
+        (match input
+          ((name (? package? p) sub-drv ...)
+           ;; XXX: Check whether P's build system knows #:implicit-inputs, for
+           ;; things like `cross-pkg-config'.
+           (if (eq? (package-build-system p) gnu-build-system)
+               (cons* name (loop p) sub-drv)
+               (cons* name p sub-drv)))
+          (x x))))
 
     (package (inherit p)
       (location (if (pair? loc) (source-properties->location loc) loc))
@@ -393,22 +393,21 @@ packages that must not be referenced."
 ;;;
 
 (define standard-cross-packages
-  (memoize
-   (lambda (target kind)
-     "Return the list of name/package tuples to cross-build for TARGET.  KIND
+  (mlambda (target kind)
+    "Return the list of name/package tuples to cross-build for TARGET.  KIND
 is one of `host' or `target'."
-     (let* ((cross     (resolve-interface '(gnu packages cross-base)))
-            (gcc       (module-ref cross 'cross-gcc))
-            (binutils  (module-ref cross 'cross-binutils))
-            (libc      (module-ref cross 'cross-libc)))
-       (case kind
-         ((host)
-          `(("cross-gcc" ,(gcc target
-                               (binutils target)
-                               (libc target)))
-            ("cross-binutils" ,(binutils target))))
-         ((target)
-          `(("cross-libc" ,(libc target)))))))))
+    (let* ((cross     (resolve-interface '(gnu packages cross-base)))
+           (gcc       (module-ref cross 'cross-gcc))
+           (binutils  (module-ref cross 'cross-binutils))
+           (libc      (module-ref cross 'cross-libc)))
+      (case kind
+        ((host)
+         `(("cross-gcc" ,(gcc target
+                              (binutils target)
+                              (libc target)))
+           ("cross-binutils" ,(binutils target))))
+        ((target)
+         `(("cross-libc" ,(libc target))))))))
 
 (define* (gnu-cross-build store name
                           #:key
diff --git a/guix/build-system/python.scm b/guix/build-system/python.scm
index d4d3d28f2a..17173f121e 100644
--- a/guix/build-system/python.scm
+++ b/guix/build-system/python.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Andreas Enge <andreas@enge.fr>
 ;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
 ;;;
@@ -21,7 +21,7 @@
 (define-module (guix build-system python)
   #:use-module (guix store)
   #:use-module (guix utils)
-  #:use-module (guix combinators)
+  #:use-module (guix memoization)
   #:use-module (guix packages)
   #:use-module (guix derivations)
   #:use-module (guix search-paths)
@@ -87,49 +87,48 @@ pre-defined variants."
     ;; Memoize the transformations.  Failing to do that, we would build a huge
     ;; object graph with lots of duplicates, which in turns prevents us from
     ;; benefiting from memoization in 'package-derivation'.
-    (memoize                                      ;FIXME: use 'eq?'
-     (lambda (p)
-       (let* ((rewrite-if-package
-               (lambda (content)
-                 ;; CONTENT may be a file name, in which case it is returned,
-                 ;; or a package, which is rewritten with the new PYTHON and
-                 ;; NEW-PREFIX.
-                 (if (package? content)
-                     (transform content)
-                     content)))
-              (rewrite
-               (match-lambda
-                 ((name content . rest)
-                  (append (list name (rewrite-if-package content)) rest)))))
-
-         (cond
-          ;; If VARIANT-PROPERTY is present, use that.
-          ((and variant-property
-                (assoc-ref (package-properties p) variant-property))
-           => force)
-
-          ;; Otherwise build the new package object graph.
-          ((eq? (package-build-system p) python-build-system)
-           (package
-             (inherit p)
-             (location (package-location p))
-             (name (let ((name (package-name p)))
-                     (string-append new-prefix
-                                    (if (string-prefix? old-prefix name)
-                                        (substring name
-                                                   (string-length old-prefix))
-                                        name))))
-             (arguments
-              (let ((python (if (promise? python)
-                                (force python)
-                                python)))
-                (ensure-keyword-arguments (package-arguments p)
-                                          `(#:python ,python))))
-             (inputs (map rewrite (package-inputs p)))
-             (propagated-inputs (map rewrite (package-propagated-inputs p)))
-             (native-inputs (map rewrite (package-native-inputs p)))))
-          (else
-           p))))))
+    (mlambdaq (p)
+      (let* ((rewrite-if-package
+              (lambda (content)
+                ;; CONTENT may be a file name, in which case it is returned,
+                ;; or a package, which is rewritten with the new PYTHON and
+                ;; NEW-PREFIX.
+                (if (package? content)
+                    (transform content)
+                    content)))
+             (rewrite
+              (match-lambda
+                ((name content . rest)
+                 (append (list name (rewrite-if-package content)) rest)))))
+
+        (cond
+         ;; If VARIANT-PROPERTY is present, use that.
+         ((and variant-property
+               (assoc-ref (package-properties p) variant-property))
+          => force)
+
+         ;; Otherwise build the new package object graph.
+         ((eq? (package-build-system p) python-build-system)
+          (package
+            (inherit p)
+            (location (package-location p))
+            (name (let ((name (package-name p)))
+                    (string-append new-prefix
+                                   (if (string-prefix? old-prefix name)
+                                       (substring name
+                                                  (string-length old-prefix))
+                                       name))))
+            (arguments
+             (let ((python (if (promise? python)
+                               (force python)
+                               python)))
+               (ensure-keyword-arguments (package-arguments p)
+                                         `(#:python ,python))))
+            (inputs (map rewrite (package-inputs p)))
+            (propagated-inputs (map rewrite (package-propagated-inputs p)))
+            (native-inputs (map rewrite (package-native-inputs p)))))
+         (else
+          p)))))
 
   transform)
 
diff --git a/guix/build/bournish.scm b/guix/build/bournish.scm
index 51dad17ba7..e948cd03d3 100644
--- a/guix/build/bournish.scm
+++ b/guix/build/bournish.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2016 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2016 Efraim Flashner <efraim@flashner.co.il>
+;;; Copyright © 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -105,6 +106,14 @@ characters."
        ((@ (guix build utils) dump-port) port (current-output-port))
        *unspecified*)))
 
+(define (rm-command . args)
+  "Emit code for the 'rm' command."
+  (cond ((member "-r" args)
+         `(for-each (@ (guix build utils) delete-file-recursively)
+                    (list ,@(delete "-r" args))))
+        (else
+         `(for-each delete-file (list ,@args)))))
+
 (define (lines+chars port)
   "Return the number of lines and number of chars read from PORT."
   (let loop ((lines 0) (chars 0))
@@ -194,7 +203,7 @@ commands such as 'ls' and 'cd'; it lacks globbing, pipes---everything.\n"))
   `(("echo"   ,(lambda strings `(list ,@strings)))
     ("cd"     ,(lambda (dir) `(chdir ,dir)))
     ("pwd"    ,(lambda () `(getcwd)))
-    ("rm"     ,(lambda (file) `(delete-file ,file)))
+    ("rm"     ,rm-command)
     ("cp"     ,(lambda (source dest) `(copy-file ,source ,dest)))
     ("help"   ,help-command)
     ("ls"     ,ls-command)
diff --git a/guix/build/dub-build-system.scm b/guix/build/dub-build-system.scm
new file mode 100644
index 0000000000..7c7cd8803c
--- /dev/null
+++ b/guix/build/dub-build-system.scm
@@ -0,0 +1,125 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2016 David Craven <david@craven.ch>
+;;; Copyright © 2017 Danny Milosavljevic <dannym@scratchpost.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix build dub-build-system)
+  #:use-module ((guix build gnu-build-system) #:prefix gnu:)
+  #:use-module (guix build syscalls)
+  #:use-module (guix build utils)
+  #:use-module (ice-9 popen)
+  #:use-module (ice-9 rdelim)
+  #:use-module (ice-9 ftw)
+  #:use-module (ice-9 format)
+  #:use-module (ice-9 match)
+  #:use-module (rnrs io ports)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:export (%standard-phases
+            dub-build))
+
+;; Commentary:
+;;
+;; Builder-side code of the DUB (the build tool for D) build system.
+;;
+;; Code:
+
+;; FIXME: Needs to be parsed from url not package name.
+(define (package-name->d-package-name name)
+  "Return the package name of NAME."
+  (match (string-split name #\-)
+    (("d" rest ...)
+     (string-join rest "-"))
+    (_ #f)))
+
+(define* (configure #:key inputs #:allow-other-keys)
+  "Prepare one new directory with all the required dependencies.
+   It's necessary to do this (instead of just using /gnu/store as the
+   directory) because we want to hide the libraries in subdirectories
+   lib/dub/... instead of polluting the user's profile root."
+  (let* ((dir (mkdtemp! "/tmp/dub.XXXXXX"))
+         (vendor-dir (string-append dir "/vendor")))
+    (setenv "HOME" dir)
+    (mkdir vendor-dir)
+    (for-each
+      (match-lambda
+        ((name . path)
+         (let* ((d-package (package-name->d-package-name name))
+                (d-basename (basename path)))
+           (when (and d-package path)
+             (match (string-split (basename path) #\-)
+               ((_ ... version)
+                (symlink (string-append path "/lib/dub/" d-basename)
+                         (string-append vendor-dir "/" d-basename))))))))
+      inputs)
+    (zero? (system* "dub" "add-path" vendor-dir))))
+
+(define (grep string file-name)
+  "Find the first occurence of STRING in the file named FILE-NAME.
+   Return the position of this occurence, or #f if none was found."
+  (string-contains (call-with-input-file file-name get-string-all)
+                   string))
+
+(define (grep* string file-name)
+  "Find the first occurence of STRING in the file named FILE-NAME.
+   Return the position of this occurence, or #f if none was found.
+   If the file named FILE-NAME doesn't exist, return #f."
+  (catch 'system-error
+    (lambda ()
+      (grep string file-name))
+    (lambda args
+      #f)))
+
+(define* (build #:key (dub-build-flags '())
+                #:allow-other-keys)
+  "Build a given DUB package."
+  (if (or (grep* "sourceLibrary" "package.json")
+          (grep* "sourceLibrary" "dub.sdl") ; note: format is different!
+          (grep* "sourceLibrary" "dub.json"))
+    #t
+    (let ((status (zero? (apply system* `("dub" "build" ,@dub-build-flags)))))
+      (system* "dub" "run") ; might fail for "targetType": "library"
+      status)))
+
+(define* (check #:key tests? #:allow-other-keys)
+  (if tests?
+    (zero? (system* "dub" "test"))
+    #t))
+
+(define* (install #:key inputs outputs #:allow-other-keys)
+  "Install a given DUB package."
+  (let* ((out (assoc-ref outputs "out"))
+         (outbin (string-append out "/bin"))
+         (outlib (string-append out "/lib/dub/" (basename out))))
+    (mkdir-p outbin)
+    ;; TODO remove "-test-application"
+    (copy-recursively "bin" outbin)
+    (mkdir-p outlib)
+    (copy-recursively "." (string-append outlib))
+    #t))
+
+(define %standard-phases
+  (modify-phases gnu:%standard-phases
+    (replace 'configure configure)
+    (replace 'build build)
+    (replace 'check check)
+    (replace 'install install)))
+
+(define* (dub-build #:key inputs (phases %standard-phases)
+                      #:allow-other-keys #:rest args)
+  "Build the given DUB package, applying all of PHASES in order."
+  (apply gnu:gnu-build #:inputs inputs #:phases phases args))
diff --git a/guix/build/r-build-system.scm b/guix/build/r-build-system.scm
index 3fc13eb835..24aa73d4f2 100644
--- a/guix/build/r-build-system.scm
+++ b/guix/build/r-build-system.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015 Ricardo Wurmus <rekado@elephly.net>
+;;; Copyright © 2015, 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -84,6 +84,7 @@
          (params       (append configure-flags
                                (list "--install-tests"
                                      (string-append "--library=" site-library)
+                                     "--built-timestamp=1970-01-01"
                                      ".")))
          (site-path    (string-append site-library ":"
                                       (generate-site-path inputs))))
diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 2e37846ff0..b68c48a05a 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -21,10 +21,12 @@
 (define-module (guix build syscalls)
   #:use-module (system foreign)
   #:use-module (rnrs bytevectors)
+  #:autoload   (ice-9 binary-ports) (get-bytevector-n)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9)
   #:use-module (srfi srfi-9 gnu)
   #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-19)
   #:use-module (ice-9 rdelim)
   #:use-module (ice-9 regex)
   #:use-module (ice-9 match)
@@ -126,7 +128,23 @@
             window-size-x-pixels
             window-size-y-pixels
             terminal-window-size
-            terminal-columns))
+            terminal-columns
+
+            utmpx?
+            utmpx-login-type
+            utmpx-pid
+            utmpx-line
+            utmpx-id
+            utmpx-user
+            utmpx-host
+            utmpx-termination-status
+            utmpx-exit-status
+            utmpx-session-id
+            utmpx-time
+            utmpx-address
+            login-type
+            utmpx-entries
+            (read-utmpx-from-port . read-utmpx)))
 
 ;;; Commentary:
 ;;;
@@ -900,6 +918,15 @@ bytevector BV at INDEX."
   ;; The most terrible interface, live from Scheme.
   (syscall->procedure int "ioctl" (list int unsigned-long '*)))
 
+(define (bytes->string bytes)
+  "Read BYTES, a list of bytes, and return the null-terminated string decoded
+from there, or #f if that would be an empty string."
+  (match (take-while (negate zero?) bytes)
+    (()
+     #f)
+    (non-zero
+     (list->string (map integer->char non-zero)))))
+
 (define (bytevector->string-list bv stride len)
   "Return the null-terminated strings found in BV every STRIDE bytes.  Read at
 most LEN bytes from BV."
@@ -911,9 +938,7 @@ most LEN bytes from BV."
        (reverse result))
       (_
        (loop (drop bytes stride)
-             (cons (list->string (map integer->char
-                                      (take-while (negate zero?) bytes)))
-                   result))))))
+             (cons (bytes->string bytes) result))))))
 
 (define* (network-interface-names #:optional sock)
   "Return the names of existing network interfaces.  This is typically limited
@@ -1480,4 +1505,108 @@ always a positive integer."
             (fall-back)
             (apply throw args))))))
 
+
+;;;
+;;; utmpx.
+;;;
+
+(define-record-type <utmpx-entry>
+  (utmpx type pid line id user host termination exit
+         session time address)
+  utmpx?
+  (type           utmpx-login-type)               ;login-type
+  (pid            utmpx-pid)
+  (line           utmpx-line)                     ;device name
+  (id             utmpx-id)
+  (user           utmpx-user)                     ;user name
+  (host           utmpx-host)                     ;host name | #f
+  (termination    utmpx-termination-status)
+  (exit           utmpx-exit-status)
+  (session        utmpx-session-id)               ;session ID, for windowing
+  (time           utmpx-time)                     ;entry time
+  (address        utmpx-address))
+
+(define-c-struct %utmpx                           ;<utmpx.h>
+  sizeof-utmpx
+  (lambda (type pid line id user host termination exit session
+                seconds useconds address %reserved)
+    (utmpx type pid
+           (bytes->string line) id
+           (bytes->string user)
+           (bytes->string host) termination exit
+           session
+           (make-time time-utc (* 1000 useconds) seconds)
+           address))
+  read-utmpx
+  write-utmpx!
+  (type           short)
+  (pid            int)
+  (line           (array uint8 32))
+  (id             (array uint8 4))
+  (user           (array uint8 32))
+  (host           (array uint8 256))
+  (termination    short)
+  (exit           short)
+  (session        int32)
+  (time-seconds   int32)
+  (time-useconds  int32)
+  (address-v6     (array int32 4))
+  (%reserved      (array uint8 20)))
+
+(define-bits login-type
+  %unused-login-type->symbols
+  (define EMPTY 0)                      ;No valid user accounting information.
+  (define RUN_LVL 1)                    ;The system's runlevel.
+  (define BOOT_TIME 2)                  ;Time of system boot.
+  (define NEW_TIME 3)                   ;Time after system clock changed.
+  (define OLD_TIME 4)                   ;Time when system clock changed.
+
+  (define INIT_PROCESS 5)                ;Process spawned by the init process.
+  (define LOGIN_PROCESS 6)               ;Session leader of a logged in user.
+  (define USER_PROCESS 7)                ;Normal process.
+  (define DEAD_PROCESS 8)                ;Terminated process.
+
+  (define ACCOUNTING 9))                 ;System accounting.
+
+(define setutxent
+  (let ((proc (syscall->procedure void "setutxent" '())))
+    (lambda ()
+      "Open the user accounting database."
+      (proc))))
+
+(define endutxent
+  (let ((proc (syscall->procedure void "endutxent" '())))
+    (lambda ()
+      "Close the user accounting database."
+      (proc))))
+
+(define getutxent
+  (let ((proc (syscall->procedure '* "getutxent" '())))
+    (lambda ()
+      "Return the next entry from the user accounting database."
+      (let ((ptr (proc)))
+        (if (null-pointer? ptr)
+            #f
+            (read-utmpx (pointer->bytevector ptr sizeof-utmpx)))))))
+
+(define (utmpx-entries)
+  "Return the list of entries read from the user accounting database."
+  (setutxent)
+  (let loop ((entries '()))
+    (match (getutxent)
+      (#f
+       (endutxent)
+       (reverse entries))
+      ((? utmpx? entry)
+       (loop (cons entry entries))))))
+
+(define (read-utmpx-from-port port)
+  "Read a utmpx entry from PORT.  Return either the EOF object or a utmpx
+entry."
+  (match (get-bytevector-n port sizeof-utmpx)
+    ((? eof-object? eof)
+     eof)
+    ((? bytevector? bv)
+     (read-utmpx bv))))
+
 ;;; syscalls.scm ends here
diff --git a/guix/combinators.scm b/guix/combinators.scm
index 9e4689ba9c..11cad62ccf 100644
--- a/guix/combinators.scm
+++ b/guix/combinators.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -20,8 +20,7 @@
 (define-module (guix combinators)
   #:use-module (ice-9 match)
   #:use-module (ice-9 vlist)
-  #:export (memoize
-            fold2
+  #:export (fold2
             fold-tree
             fold-tree-leaves
             compile-time-value))
@@ -33,19 +32,6 @@
 ;;;
 ;;; Code:
 
-(define (memoize proc)
-  "Return a memoizing version of PROC."
-  (let ((cache (make-hash-table)))
-    (lambda args
-      (let ((results (hash-ref cache args)))
-        (if results
-            (apply values results)
-            (let ((results (call-with-values (lambda ()
-                                               (apply proc args))
-                             list)))
-              (hash-set! cache args results)
-              (apply values results)))))))
-
 (define fold2
   (case-lambda
     ((proc seed1 seed2 lst)
diff --git a/guix/derivations.scm b/guix/derivations.scm
index b712c508e5..47a783f42f 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -31,6 +31,7 @@
   #:use-module (ice-9 vlist)
   #:use-module (guix store)
   #:use-module (guix utils)
+  #:use-module (guix memoization)
   #:use-module (guix combinators)
   #:use-module (guix monads)
   #:use-module (guix hash)
@@ -556,12 +557,11 @@ that form."
      (display ")" port))))
 
 (define derivation->string
-  (memoize
-   (lambda (drv)
-     "Return the external representation of DRV as a string."
-     (with-fluids ((%default-port-encoding "UTF-8"))
-       (call-with-output-string
-        (cut write-derivation drv <>))))))
+  (mlambda (drv)
+    "Return the external representation of DRV as a string."
+    (with-fluids ((%default-port-encoding "UTF-8"))
+      (call-with-output-string
+        (cut write-derivation drv <>)))))
 
 (define* (derivation->output-path drv #:optional (output "out"))
   "Return the store path of its output OUTPUT.  Raise a
@@ -583,12 +583,14 @@ DRV."
 
 (define derivation-path->output-path
   ;; This procedure is called frequently, so memoize it.
-  (memoize
-   (lambda* (path #:optional (output "out"))
-     "Read the derivation from PATH (`/gnu/store/xxx.drv'), and return the store
+  (let ((memoized (mlambda (path output)
+                    (derivation->output-path (call-with-input-file path
+                                               read-derivation)
+                                             output))))
+    (lambda* (path #:optional (output "out"))
+      "Read the derivation from PATH (`/gnu/store/xxx.drv'), and return the store
 path of its output OUTPUT."
-     (derivation->output-path (call-with-input-file path read-derivation)
-                              output))))
+      (memoized path output))))
 
 (define (derivation-path->output-paths path)
   "Read the derivation from PATH (`/gnu/store/xxx.drv'), and return the
@@ -615,23 +617,21 @@ in SIZE bytes."
           (loop (+ 1 i))))))
 
 (define derivation-path->base16-hash
-  (memoize
-   (lambda (file)
-     "Return a string containing the base16 representation of the hash of the
+  (mlambda (file)
+    "Return a string containing the base16 representation of the hash of the
 derivation at FILE."
-     (call-with-input-file file
-       (compose bytevector->base16-string
-                derivation-hash
-                read-derivation)))))
+    (call-with-input-file file
+      (compose bytevector->base16-string
+               derivation-hash
+               read-derivation))))
 
 (define derivation-hash            ; `hashDerivationModulo' in derivations.cc
-  (memoize
-   (lambda (drv)
+  (mlambda (drv)
     "Return the hash of DRV, modulo its fixed-output inputs, as a bytevector."
     (match drv
       (($ <derivation> ((_ . ($ <derivation-output> path
-                                (? symbol? hash-algo) (? bytevector? hash)
-                                (? boolean? recursive?)))))
+                                                    (? symbol? hash-algo) (? bytevector? hash)
+                                                    (? boolean? recursive?)))))
        ;; A fixed-output derivation.
        (sha256
         (string->utf8
@@ -641,14 +641,14 @@ derivation at FILE."
                         ":" (bytevector->base16-string hash)
                         ":" path))))
       (($ <derivation> outputs inputs sources
-          system builder args env-vars)
+                       system builder args env-vars)
        ;; A regular derivation: replace the path of each input with that
        ;; input's hash; return the hash of serialization of the resulting
        ;; derivation.
        (let* ((inputs (map (match-lambda
-                            (($ <derivation-input> path sub-drvs)
-                             (let ((hash (derivation-path->base16-hash path)))
-                               (make-derivation-input hash sub-drvs))))
+                             (($ <derivation-input> path sub-drvs)
+                              (let ((hash (derivation-path->base16-hash path)))
+                                (make-derivation-input hash sub-drvs))))
                            inputs))
               (drv    (make-derivation outputs
                                        (sort (coalesce-duplicate-inputs inputs)
@@ -661,7 +661,7 @@ derivation at FILE."
          ;; the SHA256 port's `write' method gets called for every single
          ;; character.
          (sha256
-          (string->utf8 (derivation->string drv)))))))))
+          (string->utf8 (derivation->string drv))))))))
 
 (define (store-path type hash name)               ; makeStorePath
   "Return the store path for NAME/HASH/TYPE."
@@ -915,18 +915,17 @@ recursively."
     (define rewritten-input
       ;; Rewrite the given input according to MAPPING, and return an input
       ;; in the format used in 'derivation' calls.
-      (memoize
-       (lambda (input loop)
-         (match input
-           (($ <derivation-input> path (sub-drvs ...))
-            (match (vhash-assoc path mapping)
-              ((_ . (? derivation? replacement))
-               (cons replacement sub-drvs))
-              ((_ . replacement)
-               (list replacement))
-              (#f
-               (let* ((drv (loop (call-with-input-file path read-derivation))))
-                 (cons drv sub-drvs)))))))))
+      (mlambda (input loop)
+        (match input
+          (($ <derivation-input> path (sub-drvs ...))
+           (match (vhash-assoc path mapping)
+             ((_ . (? derivation? replacement))
+              (cons replacement sub-drvs))
+             ((_ . replacement)
+              (list replacement))
+             (#f
+              (let* ((drv (loop (call-with-input-file path read-derivation))))
+                (cons drv sub-drvs))))))))
 
     (let loop ((drv drv))
       (let* ((inputs       (map (cut rewritten-input <> loop)
@@ -1057,13 +1056,13 @@ system, imported, and appears under FINAL-PATH in the resulting store path."
 (define search-path*
   ;; A memoizing version of 'search-path' so 'imported-modules' does not end
   ;; up looking for the same files over and over again.
-  (memoize (lambda (path file)
-             "Search for FILE in PATH and memoize the result.  Raise a
+  (mlambda (path file)
+    "Search for FILE in PATH and memoize the result.  Raise a
 '&file-search-error' condition if it could not be found."
-             (or (search-path path file)
-                 (raise (condition
-                         (&file-search-error (file file)
-                                             (path path))))))))
+    (or (search-path path file)
+        (raise (condition
+                (&file-search-error (file file)
+                                    (path path)))))))
 
 (define (module->source-file-name module)
   "Return the file name corresponding to MODULE, a Guile module name (a list
diff --git a/guix/download.scm b/guix/download.scm
index e2e5cee777..813f51f489 100644
--- a/guix/download.scm
+++ b/guix/download.scm
@@ -4,6 +4,7 @@
 ;;; Copyright © 2015 Federico Beffa <beffa@fbengineering.ch>
 ;;; Copyright © 2016 Alex Griffin <a@ajgrf.com>
 ;;; Copyright © 2016 David Craven <david@craven.ch>
+;;; Copyright © 2017 Tobias Geerinckx-Rice <me@tobias.gr>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -35,6 +36,7 @@
   #:export (%mirrors
             url-fetch
             url-fetch/tarbomb
+            url-fetch/zipbomb
             download-to-store))
 
 ;;; Commentary:
@@ -86,6 +88,7 @@
        "http://ftp.belnet.be/ftp.gnome.org/"
        "http://ftp.linux.org.uk/mirrors/ftp.gnome.org/"
        "http://ftp.gnome.org/pub/GNOME/"
+       "https://download.gnome.org/"
        "http://mirror.yandex.ru/mirrors/ftp.gnome.org/")
       (hackage
        "http://hackage.haskell.org/")
@@ -485,17 +488,24 @@ in the store."
                             (guile (default-guile)))
   "Similar to 'url-fetch' but unpack the file from URL in a directory of its
 own.  This helper makes it easier to deal with \"tar bombs\"."
+  (define file-name
+    (match url
+      ((head _ ...)
+       (basename head))
+      (_
+       (basename url))))
   (define gzip
     (module-ref (resolve-interface '(gnu packages compression)) 'gzip))
   (define tar
     (module-ref (resolve-interface '(gnu packages base)) 'tar))
 
   (mlet %store-monad ((drv (url-fetch url hash-algo hash
-                                      (string-append "tarbomb-" name)
+                                      (string-append "tarbomb-"
+                                                     (or name file-name))
                                       #:system system
                                       #:guile guile)))
     ;; Take the tar bomb, and simply unpack it as a directory.
-    (gexp->derivation name
+    (gexp->derivation (or name file-name)
                       #~(begin
                           (mkdir #$output)
                           (setenv "PATH" (string-append #$gzip "/bin"))
@@ -504,6 +514,35 @@ own.  This helper makes it easier to deal with \"tar bombs\"."
                                           "xf" #$drv)))
                       #:local-build? #t)))
 
+(define* (url-fetch/zipbomb url hash-algo hash
+                            #:optional name
+                            #:key (system (%current-system))
+                            (guile (default-guile)))
+  "Similar to 'url-fetch' but unpack the zip file at URL in a directory of its
+own.  This helper makes it easier to deal with \"zip bombs\"."
+  (define file-name
+    (match url
+      ((head _ ...)
+       (basename head))
+      (_
+       (basename url))))
+  (define unzip
+    (module-ref (resolve-interface '(gnu packages zip)) 'unzip))
+
+  (mlet %store-monad ((drv (url-fetch url hash-algo hash
+                                      (string-append "zipbomb-"
+                                                     (or name file-name))
+                                      #:system system
+                                      #:guile guile)))
+    ;; Take the zip bomb, and simply unpack it as a directory.
+    (gexp->derivation (or name file-name)
+                      #~(begin
+                          (mkdir #$output)
+                          (chdir #$output)
+                          (zero? (system* (string-append #$unzip "/bin/unzip")
+                                          #$drv)))
+                      #:local-build? #t)))
+
 (define* (download-to-store store url #:optional (name (basename url))
                             #:key (log (current-error-port)) recursive?
                             (verify-certificate? #t))
diff --git a/guix/git-download.scm b/guix/git-download.scm
index 62e625c715..5d86ab2b62 100644
--- a/guix/git-download.scm
+++ b/guix/git-download.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2017 Mathieu Lirzin <mthl@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -17,6 +18,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix git-download)
+  #:use-module (guix build utils)
   #:use-module (guix gexp)
   #:use-module (guix store)
   #:use-module (guix monads)
@@ -24,6 +26,9 @@
   #:use-module (guix packages)
   #:autoload   (guix build-system gnu) (standard-packages)
   #:use-module (ice-9 match)
+  #:use-module (ice-9 popen)
+  #:use-module (ice-9 rdelim)
+  #:use-module (srfi srfi-1)
   #:export (git-reference
             git-reference?
             git-reference-url
@@ -32,7 +37,8 @@
 
             git-fetch
             git-version
-            git-file-name))
+            git-file-name
+            git-predicate))
 
 ;;; Commentary:
 ;;;
@@ -119,4 +125,39 @@ HASH-ALGO (a symbol).  Use NAME as the file name, or a generic name if #f."
   "Return the file-name for packages using git-download."
   (string-append name "-" version "-checkout"))
 
+(define (git-predicate directory)
+  "Return a predicate that returns true if a file is part of the Git checkout
+living at DIRECTORY.  Upon Git failure, return #f instead of a predicate.
+
+The returned predicate takes two arguments FILE and STAT where FILE is an
+absolute file name and STAT is the result of 'lstat'."
+  (define (parent-directory? thing directory)
+    ;; Return #t if DIRECTORY is the parent of THING.
+    (or (string-suffix? thing directory)
+        (and (string-index thing #\/)
+             (parent-directory? (dirname thing) directory))))
+
+  (let* ((pipe        (with-directory-excursion directory
+                        (open-pipe* OPEN_READ "git" "ls-files")))
+         (files       (let loop ((lines '()))
+                        (match (read-line pipe)
+                          ((? eof-object?)
+                           (reverse lines))
+                          (line
+                           (loop (cons line lines))))))
+         (status      (close-pipe pipe)))
+    (and (zero? status)
+         (lambda (file stat)
+           (match (stat:type stat)
+             ('directory
+              ;; 'git ls-files' does not list directories, only regular files,
+              ;; so we need this special trick.
+              (any (lambda (f) (parent-directory? f file))
+                   files))
+             ((or 'regular 'symlink)
+              (any (lambda (f) (string-suffix? f file))
+                   files))
+             (_
+              #f))))))
+
 ;;; git-download.scm ends here
diff --git a/guix/gnu-maintenance.scm b/guix/gnu-maintenance.scm
index 789724c8c0..07e6909641 100644
--- a/guix/gnu-maintenance.scm
+++ b/guix/gnu-maintenance.scm
@@ -30,7 +30,7 @@
   #:use-module (guix http-client)
   #:use-module (guix ftp-client)
   #:use-module (guix utils)
-  #:use-module (guix combinators)
+  #:use-module (guix memoization)
   #:use-module (guix records)
   #:use-module (guix upstream)
   #:use-module (guix packages)
@@ -165,43 +165,48 @@ found."
         (official-gnu-packages)))
 
 (define gnu-package?
-  (memoize
-   (let ((official-gnu-packages (memoize official-gnu-packages)))
-     (lambda (package)
-       "Return true if PACKAGE is a GNU package.  This procedure may access the
+  (let ((official-gnu-packages (memoize official-gnu-packages)))
+    (mlambdaq (package)
+      "Return true if PACKAGE is a GNU package.  This procedure may access the
 network to check in GNU's database."
-       (define (mirror-type url)
-         (let ((uri (string->uri url)))
-           (and (eq? (uri-scheme uri) 'mirror)
-                (cond
-                 ((member (uri-host uri)
-                          '("gnu" "gnupg" "gcc" "gnome"))
-                  ;; Definitely GNU.
-                  'gnu)
-                 ((equal? (uri-host uri) "cran")
-                  ;; Possibly GNU: mirror://cran could be either GNU R itself
-                  ;; or a non-GNU package.
-                  #f)
-                 (else
-                  ;; Definitely non-GNU.
-                  'non-gnu)))))
-
-       (define (gnu-home-page? package)
-         (and=> (package-home-page package)
-                (lambda (url)
-                  (and=> (uri-host (string->uri url))
-                         (lambda (host)
-                           (member host '("www.gnu.org" "gnu.org")))))))
-
-       (or (gnu-home-page? package)
-           (let ((url  (and=> (package-source package) origin-uri))
-                 (name (package-name package)))
-             (case (and (string? url) (mirror-type url))
-               ((gnu) #t)
-               ((non-gnu) #f)
-               (else
-                (and (member name (map gnu-package-name (official-gnu-packages)))
-                     #t)))))))))
+      (define (mirror-type url)
+        (let ((uri (string->uri url)))
+          (and (eq? (uri-scheme uri) 'mirror)
+               (cond
+                ((member (uri-host uri)
+                         '("gnu" "gnupg" "gcc" "gnome"))
+                 ;; Definitely GNU.
+                 'gnu)
+                ((equal? (uri-host uri) "cran")
+                 ;; Possibly GNU: mirror://cran could be either GNU R itself
+                 ;; or a non-GNU package.
+                 #f)
+                (else
+                 ;; Definitely non-GNU.
+                 'non-gnu)))))
+
+      (define (gnu-home-page? package)
+        (letrec-syntax ((>> (syntax-rules ()
+                              ((_ value proc)
+                               (and=> value proc))
+                              ((_ value proc rest ...)
+                               (and=> value
+                                      (lambda (next)
+                                        (>> (proc next) rest ...)))))))
+          (>> package package-home-page
+              string->uri uri-host
+              (lambda (host)
+                (member host '("www.gnu.org" "gnu.org"))))))
+
+      (or (gnu-home-page? package)
+          (let ((url  (and=> (package-source package) origin-uri))
+                (name (package-upstream-name package)))
+            (case (and (string? url) (mirror-type url))
+              ((gnu) #t)
+              ((non-gnu) #f)
+              (else
+               (and (member name (map gnu-package-name (official-gnu-packages)))
+                    #t))))))))
 
 
 ;;;
@@ -210,10 +215,11 @@ network to check in GNU's database."
 
 (define (ftp-server/directory package)
   "Return the FTP server and directory where PACKAGE's tarball are stored."
-  (values (or (assoc-ref (package-properties package) 'ftp-server)
-              "ftp.gnu.org")
-          (or (assoc-ref (package-properties package) 'ftp-directory)
-              (string-append "/gnu/" (package-name package)))))
+  (let ((name (package-upstream-name package)))
+    (values (or (assoc-ref (package-properties package) 'ftp-server)
+                "ftp.gnu.org")
+            (or (assoc-ref (package-properties package) 'ftp-directory)
+                (string-append "/gnu/" name)))))
 
 (define (sans-extension tarball)
   "Return TARBALL without its .tar.* or .zip extension."
@@ -423,11 +429,9 @@ hosted on ftp.gnu.org, or not under that name (this is the case for
 \"emacs-auctex\", for instance.)"
   (let-values (((server directory)
                 (ftp-server/directory package)))
-    (let ((name (or (assoc-ref (package-properties package) 'upstream-name)
-                    (package-name package))))
-      (false-if-ftp-error (latest-release name
-                                          #:server server
-                                          #:directory directory)))))
+    (false-if-ftp-error (latest-release (package-upstream-name package)
+                                        #:server server
+                                        #:directory directory))))
 
 (define %package-name-rx
   ;; Regexp for a package name, e.g., "foo-X.Y".  Since TeXmacs uses
@@ -444,8 +448,10 @@ hosted on ftp.gnu.org, or not under that name (this is the case for
 (define (pure-gnu-package? package)
   "Return true if PACKAGE is a non-Emacs and non-GNOME GNU package.  This
 excludes AucTeX, for instance, whose releases are now uploaded to
-elpa.gnu.org, and all the GNOME packages."
-  (and (not (string-prefix? "emacs-" (package-name package)))
+elpa.gnu.org, and all the GNOME packages; EMMS is included though, because its
+releases are on gnu.org."
+  (and (or (not (string-prefix? "emacs-" (package-name package)))
+           (gnu-hosted? package))
        (not (gnome-package? package))
        (gnu-package? package)))
 
@@ -467,6 +473,9 @@ source URLs starts with PREFIX."
          (_                 #f)))
       (_ #f))))
 
+(define gnu-hosted?
+  (url-prefix-predicate "mirror://gnu/"))
+
 (define gnome-package?
   (url-prefix-predicate "mirror://gnome/"))
 
@@ -491,8 +500,7 @@ source URLs starts with PREFIX."
 
   (define upstream-name
     ;; Some packages like "NetworkManager" have camel-case names.
-    (or (assoc-ref (package-properties package) 'upstream-name)
-        (package-name package)))
+    (package-upstream-name package))
 
   (false-if-ftp-error
    (latest-ftp-release upstream-name
@@ -516,8 +524,7 @@ source URLs starts with PREFIX."
   (let ((uri (string->uri (origin-uri (package-source package)))))
     (false-if-ftp-error
      (latest-ftp-release
-      (or (assoc-ref (package-properties package) 'upstream-name)
-          (package-name package))
+      (package-upstream-name package)
       #:server "mirrors.mit.edu"
       #:directory
       (string-append "/kde" (dirname (dirname (uri-path uri))))
diff --git a/guix/grafts.scm b/guix/grafts.scm
index 2006d3908e..11885db226 100644
--- a/guix/grafts.scm
+++ b/guix/grafts.scm
@@ -78,11 +78,12 @@
 (define* (graft-derivation/shallow store drv grafts
                                    #:key
                                    (name (derivation-name drv))
+                                   (outputs (derivation-output-names drv))
                                    (guile (%guile-for-build))
                                    (system (%current-system)))
-  "Return a derivation called NAME, based on DRV but with all the GRAFTS
-applied.  This procedure performs \"shallow\" grafting in that GRAFTS are not
-recursively applied to dependencies of DRV."
+  "Return a derivation called NAME, which applies GRAFTS to the specified
+OUTPUTS of DRV.  This procedure performs \"shallow\" grafting in that GRAFTS
+are not recursively applied to dependencies of DRV."
   ;; XXX: Someday rewrite using gexps.
   (define mapping
     ;; List of store item pairs.
@@ -96,14 +97,12 @@ recursively applied to dependencies of DRV."
                      target))))
          grafts))
 
-  (define outputs
-    (map (match-lambda
-           ((name . output)
-            (cons name (derivation-output-path output))))
-         (derivation-outputs drv)))
-
-  (define output-names
-    (derivation-output-names drv))
+  (define output-pairs
+    (map (lambda (output)
+           (cons output
+                 (derivation-output-path
+                  (assoc-ref (derivation-outputs drv) output))))
+         outputs))
 
   (define build
     `(begin
@@ -111,7 +110,7 @@ recursively applied to dependencies of DRV."
                     (guix build utils)
                     (ice-9 match))
 
-       (let* ((old-outputs ',outputs)
+       (let* ((old-outputs ',output-pairs)
               (mapping (append ',mapping
                                (map (match-lambda
                                       ((name . file)
@@ -143,10 +142,10 @@ recursively applied to dependencies of DRV."
                                                  (guix build utils))
                                      #:inputs `(,@(map (lambda (out)
                                                          `("x" ,drv ,out))
-                                                       output-names)
+                                                       outputs)
                                                 ,@(append (map add-label sources)
                                                           (map add-label targets)))
-                                     #:outputs output-names
+                                     #:outputs outputs
                                      #:local-build? #t)))))
 (define (item->deriver store item)
   "Return two values: the derivation that led to ITEM (a store item), and the
@@ -217,13 +216,15 @@ available."
 (define-syntax-rule (with-cache key exp ...)
   "Cache the value of monadic expression EXP under KEY."
   (mlet %state-monad ((cache (current-state)))
-    (match (vhash-assq key cache)
+    (match (vhash-assoc key cache)
       ((_ . result)                               ;cache hit
        (return result))
       (#f                                         ;cache miss
-       (mlet %state-monad ((result (begin exp ...)))
-         (set-current-state (vhash-consq key result cache))
-         (return result))))))
+       (mlet %state-monad ((result (begin exp ...))
+                           (cache  (current-state)))
+         (mbegin %state-monad
+           (set-current-state (vhash-cons key result cache))
+           (return result)))))))
 
 (define* (cumulative-grafts store drv grafts
                             references
@@ -263,7 +264,7 @@ derivations to the corresponding set of grafts."
                                  #:system system))
           (state-return grafts))))
 
-  (with-cache drv
+  (with-cache (cons (derivation-file-name drv) outputs)
     (match (non-self-references references drv outputs)
       (()                                         ;no dependencies
        (return grafts))
@@ -280,29 +281,27 @@ derivations to the corresponding set of grafts."
               ;; applicable to DRV, to avoid creating several identical
               ;; grafted variants of DRV.
               (let* ((new    (graft-derivation/shallow store drv applicable
+                                                       #:outputs outputs
                                                        #:guile guile
                                                        #:system system))
-
-                     ;; Replace references to any of the outputs of DRV,
-                     ;; even if that's more than needed.  This is so that
-                     ;; the result refers only to the outputs of NEW and
-                     ;; not to those of DRV.
                      (grafts (append (map (lambda (output)
                                             (graft
                                               (origin drv)
                                               (origin-output output)
                                               (replacement new)
                                               (replacement-output output)))
-                                          (derivation-output-names drv))
+                                          outputs)
                                      grafts)))
                 (return grafts))))))))))
 
 (define* (graft-derivation store drv grafts
-                           #:key (guile (%guile-for-build))
+                           #:key
+                           (guile (%guile-for-build))
+                           (outputs (derivation-output-names drv))
                            (system (%current-system)))
-  "Applied GRAFTS to DRV and all its dependencies, recursively.  That is, if
-GRAFTS apply only indirectly to DRV, graft the dependencies of DRV, and graft
-DRV itself to refer to those grafted dependencies."
+  "Apply GRAFTS to the OUTPUTS of DRV and all their dependencies, recursively.
+That is, if GRAFTS apply only indirectly to DRV, graft the dependencies of
+DRV, and graft DRV itself to refer to those grafted dependencies."
 
   ;; First, pre-compute the dependency tree of the outputs of DRV.  Do this
   ;; upfront to have as much parallelism as possible when querying substitute
@@ -312,6 +311,7 @@ DRV itself to refer to those grafted dependencies."
 
   (match (run-with-state
              (cumulative-grafts store drv grafts references
+                                #:outputs outputs
                                 #:guile guile #:system system)
            vlist-null)                            ;the initial cache
     ((first . rest)
diff --git a/guix/http-client.scm b/guix/http-client.scm
index 0090783524..78d39a0208 100644
--- a/guix/http-client.scm
+++ b/guix/http-client.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2012, 2015 Free Software Foundation, Inc.
 ;;;
@@ -223,13 +223,14 @@ or if EOF is reached."
                 'shutdown (const #f))
 
 (define* (http-fetch uri #:key port (text? #f) (buffered? #t)
-                     keep-alive? (verify-certificate? #t))
+                     keep-alive? (verify-certificate? #t)
+                     (headers '((user-agent . "GNU Guile"))))
   "Return an input port containing the data at URI, and the expected number of
 bytes available or #f.  If TEXT? is true, the data at URI is considered to be
 textual.  Follow any HTTP redirection.  When BUFFERED? is #f, return an
 unbuffered port, suitable for use in `filtered-port'.  When KEEP-ALIVE? is
 true, send a 'Connection: keep-alive' HTTP header, in which case PORT may be
-reused for future HTTP requests.
+reused for future HTTP requests.  HEADERS is an alist of extra HTTP headers.
 
 When VERIFY-CERTIFICATE? is true, verify HTTPS server certificates.
 
@@ -240,13 +241,14 @@ Raise an '&http-get-error' condition if downloading fails."
     (let ((port (or port (open-connection-for-uri uri
                                                   #:verify-certificate?
                                                   verify-certificate?)))
-          (auth-header (match (uri-userinfo uri)
-                         ((? string? str)
-                          (list (cons 'Authorization
-                                      (string-append "Basic "
-                                                     (base64-encode
-                                                      (string->utf8 str))))))
-                         (_ '()))))
+          (headers (match (uri-userinfo uri)
+                     ((? string? str)
+                      (cons (cons 'Authorization
+                                  (string-append "Basic "
+                                                 (base64-encode
+                                                  (string->utf8 str))))
+                            headers))
+                     (_ headers))))
       (unless (or buffered? (not (file-port? port)))
         (setvbuf port _IONBF))
       (let*-values (((resp data)
@@ -254,10 +256,10 @@ Raise an '&http-get-error' condition if downloading fails."
                      (if (guile-version>? "2.0.7")
                          (http-get uri #:streaming? #t #:port port
                                    #:keep-alive? #t
-                                   #:headers auth-header) ; 2.0.9+
+                                   #:headers headers)        ; 2.0.9+
                          (http-get* uri #:decode-body? text?        ; 2.0.7
                                     #:keep-alive? #t
-                                    #:port port #:headers auth-header)))
+                                    #:port port #:headers headers)))
                     ((code)
                      (response-code resp)))
         (case code
diff --git a/guix/import/cran.scm b/guix/import/cran.scm
index 463a25514e..40cdea029b 100644
--- a/guix/import/cran.scm
+++ b/guix/import/cran.scm
@@ -1,6 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2015, 2016 Ricardo Wurmus <rekado@elephly.net>
-;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -27,7 +27,7 @@
   #:use-module (srfi srfi-41)
   #:use-module (ice-9 receive)
   #:use-module (web uri)
-  #:use-module (guix combinators)
+  #:use-module (guix memoization)
   #:use-module (guix http-client)
   #:use-module (guix hash)
   #:use-module (guix store)
diff --git a/guix/import/elpa.scm b/guix/import/elpa.scm
index 96cf5bbae6..c0b0c415cf 100644
--- a/guix/import/elpa.scm
+++ b/guix/import/elpa.scm
@@ -1,6 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2015 Federico Beffa <beffa@fbengineering.ch>
-;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -35,7 +35,6 @@
   #:use-module (guix base32)
   #:use-module (guix upstream)
   #:use-module (guix packages)
-  #:use-module ((guix combinators) #:select (memoize))
   #:use-module ((guix utils) #:select (call-with-temporary-output-file))
   #:export (elpa->guix-package
             %elpa-updater))
diff --git a/guix/import/github.scm b/guix/import/github.scm
index 01452b12e3..b249b39067 100644
--- a/guix/import/github.scm
+++ b/guix/import/github.scm
@@ -19,21 +19,38 @@
 (define-module (guix import github)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-34)
   #:use-module (json)
   #:use-module (guix utils)
   #:use-module ((guix download) #:prefix download:)
   #:use-module (guix import utils)
-  #:use-module (guix import json)
   #:use-module (guix packages)
   #:use-module (guix upstream)
+  #:use-module (guix http-client)
   #:use-module (web uri)
   #:export (%github-updater))
 
+(define (json-fetch* url)
+  "Return a representation of the JSON resource URL (a list or hash table), or
+#f if URL returns 403 or 404."
+  (guard (c ((and (http-get-error? c)
+                  (let ((error (http-get-error-code c)))
+                    (or (= 403 error)
+                        (= 404 error))))
+             #f))     ;; "expected" if there is an authentification error (403),
+                      ;; or if package is unknown (404).
+    ;; Note: github.com returns 403 if we omit a 'User-Agent' header.
+    (let* ((port   (http-fetch url))
+           (result (json->scm port)))
+      (close-port port)
+      result)))
+
 (define (find-extension url)
   "Return the extension of the archive e.g. '.tar.gz' given a URL, or
 false if none is recognized"
   (find (lambda (x) (string-suffix? x url))
-        (list ".tar.gz" ".tar.bz2" ".tar.xz" ".zip" ".tar" ".tgz" ".love")))
+        (list ".tar.gz" ".tar.bz2" ".tar.xz" ".zip" ".tar"
+              ".tgz" ".tbz" ".love")))
 
 (define (updated-github-url old-package new-version)
   ;; Return a url for the OLD-PACKAGE with NEW-VERSION.  If no source url in
@@ -41,7 +58,7 @@ false if none is recognized"
 
   (define (updated-url url)
     (if (string-prefix? "https://github.com/" url)
-        (let ((ext     (find-extension url))
+        (let ((ext     (or (find-extension url) ""))
               (name    (package-name old-package))
               (version (package-version old-package))
               (prefix  (string-append "https://github.com/"
@@ -125,7 +142,7 @@ the package e.g. 'bedtools2'.  Return #f if there is no releases"
                    "https://api.github.com/repos/"
                    (github-user-slash-repository url)
                    "/releases"))
-         (json (json-fetch
+         (json (json-fetch*
                 (if token
                     (string-append api-url "?access_token=" token)
                     api-url))))
diff --git a/guix/import/hackage.scm b/guix/import/hackage.scm
index 9af78ea888..2c9df073d3 100644
--- a/guix/import/hackage.scm
+++ b/guix/import/hackage.scm
@@ -21,6 +21,7 @@
 (define-module (guix import hackage)
   #:use-module (ice-9 match)
   #:use-module (ice-9 regex)
+  #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-26)
   #:use-module (srfi srfi-11)
   #:use-module (srfi srfi-1)
@@ -37,7 +38,13 @@
   #:use-module (guix packages)
   #:use-module ((guix utils) #:select (call-with-temporary-output-file))
   #:export (hackage->guix-package
-            %hackage-updater))
+            %hackage-updater
+
+            guix-package->hackage-name
+            hackage-fetch
+            hackage-source-url
+            hackage-cabal-url
+            hackage-package?))
 
 (define ghc-standard-libraries
   ;; List of libraries distributed with ghc (7.10.2). We include GHC itself as
@@ -109,12 +116,15 @@ version is returned."
   "Return the Cabal file for the package NAME-VERSION, or #f on failure.  If
 the version part is omitted from the package name, then return the latest
 version."
-  (let-values (((name version) (package-name->name+version name-version)))
-    (let* ((url (hackage-cabal-url name version))
-           (port (http-fetch url))
-           (result (read-cabal (canonical-newline-port port))))
-      (close-port port)
-      result)))
+  (guard (c ((and (http-get-error? c)
+                  (= 404 (http-get-error-code c)))
+             #f))                       ;"expected" if package is unknown
+    (let-values (((name version) (package-name->name+version name-version)))
+      (let* ((url (hackage-cabal-url name version))
+             (port (http-fetch url))
+             (result (read-cabal (canonical-newline-port port))))
+        (close-port port)
+        result))))
 
 (define string->license
   ;; List of valid values from
diff --git a/guix/import/json.scm b/guix/import/json.scm
index 5940f5e48f..c76bc9313c 100644
--- a/guix/import/json.scm
+++ b/guix/import/json.scm
@@ -29,7 +29,8 @@
   (guard (c ((and (http-get-error? c)
                   (= 404 (http-get-error-code c)))
              #f))                       ;"expected" if package is unknown
-    (let* ((port (http-fetch url))
+    (let* ((port (http-fetch url #:headers '((user-agent . "GNU Guile")
+                                             (Accept . "application/json"))))
            (result (hash-table->alist (json->scm port))))
       (close-port port)
       result)))
diff --git a/guix/import/pypi.scm b/guix/import/pypi.scm
index 7cce0fc594..1e433e3fb3 100644
--- a/guix/import/pypi.scm
+++ b/guix/import/pypi.scm
@@ -1,7 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014 David Thompson <davet@gnu.org>
 ;;; Copyright © 2015 Cyril Roelandt <tipecaml@gmail.com>
-;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -89,9 +89,16 @@ package."
 (define (guix-package->pypi-name package)
   "Given a Python PACKAGE built from pypi.python.org, return the name of the
 package on PyPI."
-  (let ((source-url (and=> (package-source package) origin-uri)))
+  (define (url->pypi-name url)
     (hyphen-package-name->name+version
-     (basename (file-sans-extension source-url)))))
+     (basename (file-sans-extension url))))
+
+  (match (and=> (package-source package) origin-uri)
+    ((? string? url)
+     (url->pypi-name url))
+    ((lst ...)
+     (any url->pypi-name lst))
+    (#f #f)))
 
 (define (wheel-url->extracted-directory wheel-url)
   (match (string-split (basename wheel-url) #\-)
@@ -227,10 +234,8 @@ name/variable pairs describing the required inputs of this package."
   (sort
     (map (lambda (input)
            (list input (list 'unquote (string->symbol input))))
-         (append '("python-setuptools")
-                 ;; Argparse has been part of Python since 2.7.
-                 (remove (cut string=? "python-argparse" <>)
-                         (guess-requirements source-url wheel-url tarball))))
+         (remove (cut string=? "python-argparse" <>)
+                 (guess-requirements source-url wheel-url tarball)))
     (lambda args
       (match args
         (((a _ ...) (b _ ...))
diff --git a/guix/import/stackage.scm b/guix/import/stackage.scm
new file mode 100644
index 0000000000..542b718083
--- /dev/null
+++ b/guix/import/stackage.scm
@@ -0,0 +1,135 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 Federico Beffa <beffa@fbengineering.ch>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix import stackage)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 regex)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:use-module (guix import json)
+  #:use-module (guix import hackage)
+  #:use-module (guix memoization)
+  #:use-module (guix packages)
+  #:use-module (guix upstream)
+  #:use-module (guix ui)
+  #:export (stackage->guix-package
+            %stackage-updater))
+
+
+;;;
+;;; Stackage info fetcher and access functions
+;;;
+
+(define %stackage-url "http://www.stackage.org")
+
+(define (lts-info-ghc-version lts-info)
+  "Retruns the version of the GHC compiler contained in LTS-INFO."
+  (match lts-info
+    ((("snapshot" ("ghc" . version) _ _) _)  version)
+    (_ #f)))
+
+(define (lts-info-packages lts-info)
+  "Retruns the alist of packages contained in LTS-INFO."
+  (match lts-info
+    ((_ ("packages" pkg ...)) pkg)
+    (_ '())))
+
+(define stackage-lts-info-fetch
+  ;; "Retrieve the information about the LTS Stackage release VERSION."
+  (memoize
+   (lambda* (#:optional (version ""))
+     (let* ((url (if (string=? "" version)
+                     (string-append %stackage-url "/lts")
+                     (string-append %stackage-url "/lts-" version)))
+            (lts-info (json-fetch url)))
+       (if lts-info
+           (reverse lts-info)
+           (leave (_ "LTS release version not found: ~A~%") version))))))
+
+(define (stackage-package-name pkg-info)
+  (assoc-ref pkg-info "name"))
+
+(define (stackage-package-version pkg-info)
+  (assoc-ref pkg-info "version"))
+
+(define (lts-package-version pkgs-info name)
+  "Return the version of the package with upstream NAME included in PKGS-INFO."
+  (let ((pkg (find (lambda (pkg) (string=? (stackage-package-name pkg) name))
+                   pkgs-info)))
+    (stackage-package-version pkg)))
+
+
+;;;
+;;; Importer entry point
+;;;
+
+(define (hackage-name-version name version)
+  (and version (string-append  name "@" version)))
+
+(define* (stackage->guix-package package-name ; upstream name
+                                 #:key
+                                 (include-test-dependencies? #t)
+                                 (lts-version "")
+                                 (packages-info
+                                  (lts-info-packages
+                                   (stackage-lts-info-fetch lts-version))))
+  "Fetch Cabal file for PACKAGE-NAME from hackage.haskell.org.  The retrieved
+vesion corresponds to the version of PACKAGE-NAME specified in the LTS-VERSION
+release at stackage.org.  Return the `package' S-expression corresponding to
+that package, or #f on failure.  PACKAGES-INFO is the alist with the packages
+included in the Stackage LTS release."
+  (let* ((version (lts-package-version packages-info package-name))
+         (name-version (hackage-name-version package-name version)))
+    (if name-version
+        (hackage->guix-package name-version
+                               #:include-test-dependencies?
+                               include-test-dependencies?)
+        (leave (_ "package not found: ~A~%") package-name))))
+
+
+;;;
+;;; Updater
+;;;
+
+(define latest-lts-release
+  (let ((pkgs-info (mlambda () (lts-info-packages (stackage-lts-info-fetch)))))
+    (lambda* (package)
+      "Return an <upstream-source> for the latest Stackage LTS release of
+PACKAGE or #f it the package is not inlucded in the Stackage LTS release."
+      (let* ((hackage-name (guix-package->hackage-name package))
+             (version (lts-package-version (pkgs-info) hackage-name))
+             (name-version (hackage-name-version hackage-name version)))
+        (match (and=> name-version hackage-fetch)
+          (#f (format (current-error-port)
+                      "warning: failed to parse ~a~%"
+                      (hackage-cabal-url hackage-name))
+              #f)
+          (_ (let ((url (hackage-source-url hackage-name version)))
+               (upstream-source
+                (package (package-name package))
+                (version version)
+                (urls (list url))))))))))
+
+(define %stackage-updater
+  (upstream-updater
+   (name 'stackage)
+   (description "Updater for Stackage LTS packages")
+   (pred hackage-package?)
+   (latest latest-lts-release)))
+
+;;; stackage.scm ends here
diff --git a/guix/licenses.scm b/guix/licenses.scm
index 1e19300586..7b2ac2d311 100644
--- a/guix/licenses.scm
+++ b/guix/licenses.scm
@@ -8,7 +8,7 @@
 ;;; Copyright © 2016 Leo Famulari <leo@famulari.name>
 ;;; Copyright © 2016 Fabian Harfert <fhmgufs@web.de>
 ;;; Copyright © 2016 Rene Saavedra <rennes@openmailbox.org>
-;;; Copyright © 2016 ng0 <ngillmann@runbox.com>
+;;; Copyright © 2016, 2017 ng0 <ng0@libertad.pw>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -74,7 +74,8 @@
             x11 x11-style
             zpl2.1
             zlib
-            fsf-free))
+            fsf-free
+            wtfpl2))
 
 (define-record-type <license>
   (license name uri comment)
@@ -450,6 +451,11 @@ at URI, which may be a file:// URI pointing the package's tree."
            "https://unlicense.org/"
            "https://www.gnu.org/licenses/license-list.html#Unlicense"))
 
+(define wtfpl2
+  (license "WTFPL 2"
+           "http://www.wtfpl.net"
+           "http://www.wtfpl.net/about/"))
+
 (define x11
   (license "X11"
            "http://directory.fsf.org/wiki/License:X11"
diff --git a/guix/memoization.scm b/guix/memoization.scm
new file mode 100644
index 0000000000..d64f60fe9c
--- /dev/null
+++ b/guix/memoization.scm
@@ -0,0 +1,114 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix memoization)
+  #:export (memoize
+            mlambda
+            mlambdaq))
+
+(define-syntax-rule (call/mv thunk)
+  (call-with-values thunk list))
+(define-syntax-rule (return/mv lst)
+  (apply values lst))
+
+(define-syntax-rule (call/1 thunk)
+  (thunk))
+(define-syntax-rule (return/1 value)
+  value)
+
+(define %nothing                                  ;nothingness
+  (list 'this 'is 'nothing))
+
+(define-syntax define-cache-procedure
+  (syntax-rules ()
+    "Define a procedure NAME that implements a cache using HASH-REF and
+HASH-SET!.  Use CALL to invoke the thunk and RETURN to return its value; CALL
+and RETURN are used to distinguish between multiple-value and single-value
+returns."
+    ((_ name hash-ref hash-set! call return)
+     (define (name cache key thunk)
+       "Cache the result of THUNK under KEY in CACHE, or return the
+already-cached result."
+       (let ((results (hash-ref cache key %nothing)))
+         (if (eq? results %nothing)
+             (let ((results (call thunk)))
+               (hash-set! cache key results)
+               (return results))
+             (return results)))))
+    ((_ name hash-ref hash-set!)
+     (define-cache-procedure name hash-ref hash-set!
+       call/mv return/mv))))
+
+(define-cache-procedure cached/mv  hash-ref hash-set!)
+(define-cache-procedure cachedq/mv hashq-ref hashq-set!)
+(define-cache-procedure cached  hash-ref hash-set! call/1 return/1)
+(define-cache-procedure cachedq hashq-ref hashq-set! call/1 return/1)
+
+(define (memoize proc)
+  "Return a memoizing version of PROC.
+
+This is a generic version of 'mlambda' what works regardless of the arity of
+'proc'.  It is more expensive since the argument list is always allocated, and
+the result is returned via (apply values results)."
+  (let ((cache (make-hash-table)))
+    (lambda args
+      (cached/mv cache args
+                 (lambda ()
+                   (apply proc args))))))
+
+(define-syntax %mlambda
+  (syntax-rules ()
+    "Return a memoizing lambda.  This is restricted to procedures that return
+exactly one value."
+    ((_ cached () body ...)
+     ;; The zero-argument case is equivalent to a promise.
+     (let ((result #f) (cached? #f))
+       (lambda ()
+         (unless cached?
+           (set! result (begin body ...))
+           (set! cached? #t))
+         result)))
+
+    ;; Optimize the fixed-arity case such that there's no argument list
+    ;; allocated.  XXX: We can't really avoid the closure allocation since
+    ;; Guile 2.0's compiler will always keep it.
+    ((_ cached (arg) body ...)                    ;one argument
+     (let ((cache (make-hash-table))
+           (proc  (lambda (arg) body ...)))
+       (lambda (arg)
+         (cached cache arg (lambda () (proc arg))))))
+    ((_ _ (args ...) body ...)                    ;two or more arguments
+     (let ((cache (make-hash-table))
+           (proc  (lambda (args ...) body ...)))
+       (lambda (args ...)
+         ;; XXX: Always use 'cached', which uses 'equal?', to compare the
+         ;; argument lists.
+         (cached cache (list args ...)
+                 (lambda ()
+                   (proc args ...))))))))
+
+(define-syntax-rule (mlambda formals body ...)
+  "Define a memoizing lambda.  The lambda's arguments are compared with
+'equal?', and BODY is expected to yield a single return value."
+  (%mlambda cached formals body ...))
+
+(define-syntax-rule (mlambdaq formals body ...)
+  "Define a memoizing lambda.  If FORMALS lists a single argument, it is
+compared using 'eq?'; otherwise, the argument list is compared using 'equal?'.
+BODY is expected to yield a single return value."
+  (%mlambda cachedq formals body ...))
diff --git a/guix/modules.scm b/guix/modules.scm
index 24f613ff4e..8c63f21a97 100644
--- a/guix/modules.scm
+++ b/guix/modules.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -17,7 +17,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix modules)
-  #:use-module ((guix utils) #:select (memoize))
+  #:use-module (guix memoization)
   #:use-module (guix sets)
   #:use-module (srfi srfi-26)
   #:use-module (ice-9 match)
@@ -71,18 +71,17 @@ CLAUSES."
              result)))))
 
 (define module-file-dependencies
-  (memoize
-   (lambda (file)
-     "Return the list of the names of modules that the Guile module in FILE
+  (mlambda (file)
+    "Return the list of the names of modules that the Guile module in FILE
 depends on."
-     (call-with-input-file file
-       (lambda (port)
-         (match (read port)
-           (('define-module name clauses ...)
-            (extract-dependencies clauses))
-           ;; XXX: R6RS 'library' form is ignored.
-           (_
-            '())))))))
+    (call-with-input-file file
+      (lambda (port)
+        (match (read port)
+          (('define-module name clauses ...)
+           (extract-dependencies clauses))
+          ;; XXX: R6RS 'library' form is ignored.
+          (_
+           '()))))))
 
 (define (module-name->file-name module)
   "Return the file name for MODULE."
diff --git a/guix/packages.scm b/guix/packages.scm
index beb958f156..4bc4b017f4 100644
--- a/guix/packages.scm
+++ b/guix/packages.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014, 2015 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2015 Eric Bavier <bavier@member.fsf.org>
 ;;; Copyright © 2016 Alex Kost <alezost@gmail.com>
@@ -28,6 +28,7 @@
   #:use-module (guix base32)
   #:use-module (guix grafts)
   #:use-module (guix derivations)
+  #:use-module (guix memoization)
   #:use-module (guix build-system)
   #:use-module (guix search-paths)
   #:use-module (guix gexp)
@@ -62,6 +63,7 @@
             package
             package?
             package-name
+            package-upstream-name
             package-version
             package-full-name
             package-source
@@ -296,6 +298,12 @@ name of its URI."
                                                        package)
                                                       16)))))
 
+(define (package-upstream-name package)
+  "Return the upstream name of PACKAGE, which could be different from the name
+it has in Guix."
+  (or (assq-ref (package-properties package) 'upstream-name)
+      (package-name package)))
+
 (define (hidden-package p)
   "Return a \"hidden\" version of P--i.e., one that 'fold-packages' and thus,
 user interfaces, ignores."
@@ -690,38 +698,19 @@ in INPUTS and their transitive propagated inputs."
          `(assoc-ref ,alist ,(label input)))
        (transitive-inputs inputs)))
 
-(define-syntax define-memoized/v
-  (lambda (form)
-    "Define a memoized single-valued unary procedure with docstring.
-The procedure argument is compared to cached keys using `eqv?'."
-    (syntax-case form ()
-      ((_ (proc arg) docstring body body* ...)
-       (string? (syntax->datum #'docstring))
-       #'(define proc
-           (let ((cache (make-hash-table)))
-             (define (proc arg)
-               docstring
-               (match (hashv-get-handle cache arg)
-                 ((_ . value)
-                  value)
-                 (_
-                  (let ((result (let () body body* ...)))
-                    (hashv-set! cache arg result)
-                    result))))
-             proc))))))
-
-(define-memoized/v (package-transitive-supported-systems package)
-  "Return the intersection of the systems supported by PACKAGE and those
+(define package-transitive-supported-systems
+  (mlambdaq (package)
+    "Return the intersection of the systems supported by PACKAGE and those
 supported by its dependencies."
-  (fold (lambda (input systems)
-          (match input
-            ((label (? package? p) . _)
-             (lset-intersection
-              string=? systems (package-transitive-supported-systems p)))
-            (_
-             systems)))
-        (package-supported-systems package)
-        (bag-direct-inputs (package->bag package))))
+    (fold (lambda (input systems)
+            (match input
+              ((label (? package? p) . _)
+               (lset-intersection
+                string=? systems (package-transitive-supported-systems p)))
+              (_
+               systems)))
+          (package-supported-systems package)
+          (bag-direct-inputs (package->bag package)))))
 
 (define* (supported-package? package #:optional (system (%current-system)))
   "Return true if PACKAGE is supported on SYSTEM--i.e., if PACKAGE and all its
@@ -768,14 +757,15 @@ package and returns its new name after rewrite."
       (_
        input)))
 
-  (define-memoized/v (replace p)
-    "Return a variant of P with its inputs rewritten."
-    (package
-      (inherit p)
-      (name (rewrite-name (package-name p)))
-      (inputs (map rewrite (package-inputs p)))
-      (native-inputs (map rewrite (package-native-inputs p)))
-      (propagated-inputs (map rewrite (package-propagated-inputs p)))))
+  (define replace
+    (mlambdaq (p)
+      ;; Return a variant of P with its inputs rewritten.
+      (package
+        (inherit p)
+        (name (rewrite-name (package-name p)))
+        (inputs (map rewrite (package-inputs p)))
+        (native-inputs (map rewrite (package-native-inputs p)))
+        (propagated-inputs (map rewrite (package-propagated-inputs p))))))
 
   replace)
 
diff --git a/guix/profiles.scm b/guix/profiles.scm
index e7707b6543..de82eae348 100644
--- a/guix/profiles.scm
+++ b/guix/profiles.scm
@@ -92,6 +92,7 @@
             profile-manifest
             package->manifest-entry
             packages->manifest
+            ca-certificate-bundle
             %default-profile-hooks
             profile-derivation
 
@@ -738,7 +739,7 @@ for both major versions of GTK+."
   (mlet %store-monad ((gtk+   (manifest-lookup-package manifest "gtk+" "3"))
                       (gtk+-2 (manifest-lookup-package manifest "gtk+" "2")))
 
-    (define (build gtk gtk-version)
+    (define (build gtk gtk-version query)
       (let ((major (string-take gtk-version 1)))
         (with-imported-modules '((guix build utils)
                                  (guix build union)
@@ -755,8 +756,6 @@ for both major versions of GTK+."
 
               (let* ((prefix  (string-append "/lib/gtk-" #$major ".0/"
                                              #$gtk-version))
-                     (query   (string-append #$gtk "/bin/gtk-query-immodules-"
-                                             #$major ".0"))
                      (destdir (string-append #$output prefix))
                      (moddirs (cons (string-append #$gtk prefix "/immodules")
                                     (filter file-exists?
@@ -767,7 +766,7 @@ for both major versions of GTK+."
 
                 ;; Generate a new immodules cache file.
                 (mkdir-p (string-append #$output prefix))
-                (let ((pipe    (apply open-pipe* OPEN_READ query modules))
+                (let ((pipe    (apply open-pipe* OPEN_READ #$query modules))
                       (outfile (string-append #$output prefix
                                               "/immodules-gtk" #$major ".cache")))
                   (dynamic-wind
@@ -782,9 +781,23 @@ for both major versions of GTK+."
                       (close-pipe pipe)))))))))
 
     ;; Don't run the hook when there's nothing to do.
-    (let ((gexp #~(begin
-                    #$(if gtk+   (build gtk+   "3.0.0")  #t)
-                    #$(if gtk+-2 (build gtk+-2 "2.10.0") #t))))
+    (let* ((pkg-gtk+ (module-ref        ; lazy reference
+                      (resolve-interface '(gnu packages gtk)) 'gtk+))
+           (gexp #~(begin
+                     #$(if gtk+
+                           (build
+                            gtk+ "3.0.0"
+                            ;; Use 'gtk-query-immodules-3.0' from the 'bin'
+                            ;; output of latest gtk+ package.
+                            #~(string-append
+                               #$pkg-gtk+:bin "/bin/gtk-query-immodules-3.0"))
+                           #t)
+                     #$(if gtk+-2
+                           (build
+                            gtk+-2 "2.10.0"
+                            #~(string-append
+                               #$gtk+-2 "/bin/gtk-query-immodules-2.0"))
+                           #t))))
       (if (or gtk+ gtk+-2)
           (gexp->derivation "gtk-im-modules" gexp
                             #:local-build? #t
diff --git a/guix/scripts/build.scm b/guix/scripts/build.scm
index ccb4c275fc..68402fda18 100644
--- a/guix/scripts/build.scm
+++ b/guix/scripts/build.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Mark H Weaver <mhw@netris.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -24,7 +24,6 @@
   #:use-module (guix derivations)
   #:use-module (guix packages)
   #:use-module (guix grafts)
-  #:use-module (guix combinators)
 
   ;; Use the procedure that destructures "NAME-VERSION" forms.
   #:use-module ((guix utils) #:hide (package-name->name+version))
@@ -99,8 +98,10 @@ found.  Return #f if no build log was found."
 
 (define (register-root store paths root)
   "Register ROOT as an indirect GC root for all of PATHS."
-  (let* ((root (string-append (canonicalize-path (dirname root))
-                              "/" root)))
+  (let* ((root (if (string-prefix? "/" root)
+                   root
+                   (string-append (canonicalize-path (dirname root))
+                                  "/" root))))
     (catch 'system-error
       (lambda ()
         (match paths
@@ -344,8 +345,8 @@ options handled by 'set-build-options-from-command-line', and listed in
                      #:keep-failed? (assoc-ref opts 'keep-failed?)
                      #:keep-going? (assoc-ref opts 'keep-going?)
                      #:rounds (assoc-ref opts 'rounds)
-                     #:build-cores (or (assoc-ref opts 'cores) 0)
-                     #:max-build-jobs (or (assoc-ref opts 'max-jobs) 1)
+                     #:build-cores (assoc-ref opts 'cores)
+                     #:max-build-jobs (assoc-ref opts 'max-jobs)
                      #:fallback? (assoc-ref opts 'fallback?)
                      #:use-substitutes? (assoc-ref opts 'substitutes?)
                      #:substitute-urls (assoc-ref opts 'substitute-urls)
@@ -462,7 +463,6 @@ options handled by 'set-build-options-from-command-line', and listed in
     (substitutes? . #t)
     (build-hook? . #t)
     (print-build-trace? . #t)
-    (max-silent-time . 3600)
     (verbosity . 0)))
 
 (define (show-help)
@@ -487,6 +487,8 @@ Build the given PACKAGE-OR-DERIVATION and return their output paths.\n"))
   (display (_ "
       --check            rebuild items to check for non-determinism issues"))
   (display (_ "
+      --repair           repair the specified items"))
+  (display (_ "
   -r, --root=FILE        make FILE a symlink to the result, and register it
                          as a garbage collector root"))
   (display (_ "
@@ -536,6 +538,12 @@ must be one of 'package', 'all', or 'transitive'~%")
                           (alist-cons 'build-mode (build-mode check)
                                       result)
                           rest)))
+         (option '("repair") #f #f
+                 (lambda (opt name arg result . rest)
+                   (apply values
+                          (alist-cons 'build-mode (build-mode repair)
+                                      result)
+                          rest)))
          (option '(#\s "system") #t #f
                  (lambda (opt name arg result)
                    (alist-cons 'system arg
diff --git a/guix/scripts/challenge.scm b/guix/scripts/challenge.scm
index 9ab4fbe2a9..815bb789c3 100644
--- a/guix/scripts/challenge.scm
+++ b/guix/scripts/challenge.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -37,12 +37,17 @@
   #:use-module (ice-9 vlist)
   #:use-module (ice-9 format)
   #:use-module (web uri)
-  #:export (discrepancies
+  #:export (compare-contents
 
-            discrepancy?
-            discrepancy-item
-            discrepancy-local-sha256
-            discrepancy-narinfos
+            comparison-report?
+            comparison-report-item
+            comparison-report-result
+            comparison-report-local-sha256
+            comparison-report-narinfos
+
+            comparison-report-match?
+            comparison-report-mismatch?
+            comparison-report-inconclusive?
 
             guix-challenge))
 
@@ -61,13 +66,38 @@
 (define ensure-store-item                         ;XXX: move to (guix ui)?
   (@@ (guix scripts size) ensure-store-item))
 
-;; Representation of a hash mismatch for ITEM.
-(define-record-type <discrepancy>
-  (discrepancy item local-sha256 narinfos)
-  discrepancy?
-  (item         discrepancy-item)                   ;string, /gnu/store/… item
-  (local-sha256 discrepancy-local-sha256)           ;bytevector | #f
-  (narinfos     discrepancy-narinfos))              ;list of <narinfo>
+;; Representation of a comparison report for ITEM.
+(define-record-type <comparison-report>
+  (%comparison-report item result local-sha256 narinfos)
+  comparison-report?
+  (item         comparison-report-item)    ;string, /gnu/store/… item
+  (result       comparison-report-result)  ;'match | 'mismatch | 'inconclusive
+  (local-sha256 comparison-report-local-sha256)   ;bytevector | #f
+  (narinfos     comparison-report-narinfos))      ;list of <narinfo>
+
+(define-syntax comparison-report
+  ;; Some sort of a an enum to make sure 'result' is correct.
+  (syntax-rules (match mismatch inconclusive)
+    ((_ item 'match rest ...)
+     (%comparison-report item 'match rest ...))
+    ((_ item 'mismatch rest ...)
+     (%comparison-report item 'mismatch rest ...))
+    ((_ item 'inconclusive rest ...)
+     (%comparison-report item 'inconclusive rest ...))))
+
+(define (comparison-report-predicate result)
+  "Return a predicate that returns true when pass a REPORT that has RESULT."
+  (lambda (report)
+    (eq? (comparison-report-result report) result)))
+
+(define comparison-report-mismatch?
+  (comparison-report-predicate 'mismatch))
+
+(define comparison-report-match?
+  (comparison-report-predicate 'match))
+
+(define comparison-report-inconclusive?
+  (comparison-report-predicate 'inconclusive))
 
 (define (locally-built? store item)
   "Return true if ITEM was built locally."
@@ -88,10 +118,10 @@ Otherwise return #f."
 (define-syntax-rule (report args ...)
   (format (current-error-port) args ...))
 
-(define (discrepancies items servers)
+(define (compare-contents items servers)
   "Challenge the substitute servers whose URLs are listed in SERVERS by
 comparing the hash of the substitutes of ITEMS that they serve.  Return the
-list of discrepancies.
+list of <comparison-report> objects.
 
 This procedure does not authenticate narinfos from SERVERS, nor does it verify
 that they are signed by an authorized public keys.  The reason is that, by
@@ -100,11 +130,7 @@ taken since we do not import the archives."
   (define (compare item reference)
     ;; Return a procedure to compare the hash of ITEM with REFERENCE.
     (lambda (narinfo url)
-      (if (not narinfo)
-          (begin
-            (warning (_ "~a: no substitute at '~a'~%")
-                     item url)
-            #t)
+      (or (not narinfo)
           (let ((value (narinfo-hash->sha256 (narinfo-hash narinfo))))
             (bytevector=? reference value)))))
 
@@ -116,9 +142,7 @@ taken since we do not import the archives."
          ((url urls ...)
           (if (not first)
               (select-reference item narinfos urls)
-              (narinfo-hash->sha256 (narinfo-hash first))))))
-      (()
-       (warning (_ "no substitutes for '~a'; cannot conclude~%") item))))
+              (narinfo-hash->sha256 (narinfo-hash first))))))))
 
   (mlet* %store-monad ((local     (mapm %store-monad
                                         query-locally-built-hash items))
@@ -130,42 +154,61 @@ taken since we do not import the archives."
                                                         vhash))
                                           vlist-null
                                           remote)))
-    (return (filter-map (lambda (item local)
-                          (let ((narinfos (vhash-fold* cons '() item narinfos)))
-                            (define reference
-                              (or local
-                                  (begin
-                                    (warning (_ "no local build for '~a'~%") item)
-                                    (select-reference item narinfos servers))))
-
-                            (if (every (compare item reference)
-                                       narinfos servers)
-                                #f
-                                (discrepancy item local narinfos))))
-                        items
-                        local))))
-
-(define* (summarize-discrepancy discrepancy
-                                #:key (hash->string
-                                       bytevector->nix-base32-string))
-  "Write to the current error port a summary of DISCREPANCY, a <discrepancy>
-object that denotes a hash mismatch."
-  (match discrepancy
-    (($ <discrepancy> item local (narinfos ...))
+    (return (map (lambda (item local)
+                   (match (vhash-fold* cons '() item narinfos)
+                     (()                          ;no substitutes
+                      (comparison-report item 'inconclusive local '()))
+                     ((narinfo)
+                      (if local
+                          (if ((compare item local) narinfo (first servers))
+                              (comparison-report item 'match
+                                                 local (list narinfo))
+                              (comparison-report item 'mismatch
+                                                 local (list narinfo)))
+                          (comparison-report item 'inconclusive
+                                             local (list narinfo))))
+                     ((narinfos ...)
+                      (let ((reference
+                             (or local (select-reference item narinfos
+                                                         servers))))
+                        (if (every (compare item reference) narinfos servers)
+                            (comparison-report item 'match
+                                               local narinfos)
+                            (comparison-report item 'mismatch
+                                               local narinfos))))))
+                 items
+                 local))))
+
+(define* (summarize-report comparison-report
+                           #:key
+                           (hash->string bytevector->nix-base32-string)
+                           verbose?)
+  "Write to the current error port a summary of REPORT, a <comparison-report>
+object.  When VERBOSE?, display matches in addition to mismatches and
+inconclusive reports."
+  (define (report-hashes item local narinfos)
+    (if local
+        (report (_ "  local hash: ~a~%") (hash->string local))
+        (report (_ "  no local build for '~a'~%") item))
+    (for-each (lambda (narinfo)
+                (report (_ "  ~50a: ~a~%")
+                        (uri->string (narinfo-uri narinfo))
+                        (hash->string
+                         (narinfo-hash->sha256 (narinfo-hash narinfo)))))
+              narinfos))
+
+  (match comparison-report
+    (($ <comparison-report> item 'mismatch local (narinfos ...))
      (report (_ "~a contents differ:~%") item)
-     (if local
-         (report (_ "  local hash: ~a~%") (hash->string local))
-         (warning (_ "no local build for '~a'~%") item))
-
-     (for-each (lambda (narinfo)
-                 (if narinfo
-                     (report (_ "  ~50a: ~a~%")
-                             (uri->string (narinfo-uri narinfo))
-                             (hash->string
-                              (narinfo-hash->sha256 (narinfo-hash narinfo))))
-                     (report (_ "  ~50a: unavailable~%")
-                             (uri->string (narinfo-uri narinfo)))))
-               narinfos))))
+     (report-hashes item local narinfos))
+    (($ <comparison-report> item 'inconclusive #f narinfos)
+     (warning (_ "could not challenge '~a': no local build~%") item))
+    (($ <comparison-report> item 'inconclusive locals ())
+     (warning (_ "could not challenge '~a': no substitutes~%") item))
+    (($ <comparison-report> item 'match local (narinfos ...))
+     (when verbose?
+       (report (_ "~a contents match:~%") item)
+       (report-hashes item local narinfos)))))
 
 
 ;;;
@@ -178,6 +221,8 @@ Challenge the substitutes for PACKAGE... provided by one or more servers.\n"))
   (display (_ "
       --substitute-urls=URLS
                          compare build results with those at URLS"))
+  (display (_ "
+      -v, --verbose      show details about successful comparisons"))
   (newline)
   (display (_ "
   -h, --help             display this help and exit"))
@@ -201,6 +246,11 @@ Challenge the substitutes for PACKAGE... provided by one or more servers.\n"))
                           (alist-cons 'substitute-urls
                                       (string-tokenize arg)
                                       (alist-delete 'substitute-urls result))
+                          rest)))
+         (option '("verbose" #\v) #f #f
+                 (lambda (opt name arg result . rest)
+                   (apply values
+                          (alist-cons 'verbose? #t result)
                           rest)))))
 
 (define %default-options
@@ -220,7 +270,8 @@ Challenge the substitutes for PACKAGE... provided by one or more servers.\n"))
                                    (_ #f))
                                  opts))
            (system   (assoc-ref opts 'system))
-           (urls     (assoc-ref opts 'substitute-urls)))
+           (urls     (assoc-ref opts 'substitute-urls))
+           (verbose? (assoc-ref opts 'verbose?)))
       (leave-on-EPIPE
        (with-store store
          ;; Disable grafts since substitute servers normally provide only
@@ -236,13 +287,15 @@ Challenge the substitutes for PACKAGE... provided by one or more servers.\n"))
                                 #:use-substitutes? #f)
 
              (run-with-store store
-               (mlet* %store-monad ((items  (mapm %store-monad
-                                                  ensure-store-item files))
-                                    (issues (discrepancies items urls)))
-                 (for-each summarize-discrepancy issues)
-                 (unless (null? issues)
-                   (exit 2))
-                 (return (null? issues)))
+               (mlet* %store-monad ((items   (mapm %store-monad
+                                                   ensure-store-item files))
+                                    (reports (compare-contents items urls)))
+                 (for-each (cut summarize-report <> #:verbose? verbose?)
+                           reports)
+
+                 (exit (cond ((any comparison-report-mismatch? reports) 2)
+                             ((every comparison-report-match? reports) 0)
+                             (else 1))))
                #:system system))))))))
 
 ;;; challenge.scm ends here
diff --git a/guix/scripts/container/exec.scm b/guix/scripts/container/exec.scm
index 10e70568cc..d6d267daff 100644
--- a/guix/scripts/container/exec.scm
+++ b/guix/scripts/container/exec.scm
@@ -74,7 +74,14 @@ and the other containing arguments for the command to be executed."
       (let* ((opts (parse-command-line args %options '(())
                                        #:argument-handler
                                        handle-argument))
-             (pid  (assoc-ref opts 'pid)))
+             (pid  (assoc-ref opts 'pid))
+             (environment (filter-map (lambda (name)
+                                        (let ((value (getenv name)))
+                                          (and value (cons name value))))
+                                      ;; Pass through the TERM environment
+                                      ;; variable to inform processes about
+                                      ;; the capabilities of the terminal.
+                                      '("TERM"))))
 
         (unless pid
           (leave (_ "no pid specified~%")))
@@ -89,6 +96,10 @@ and the other containing arguments for the command to be executed."
                         (lambda ()
                           (match command
                             ((program . program-args)
+                             (for-each (match-lambda
+                                         ((name . value)
+                                          (setenv name value)))
+                                       environment)
                              (apply execlp program program program-args)))))))
           (unless (zero? result)
             (leave (_ "exec failed with status ~d~%") result)))))))
diff --git a/guix/scripts/copy.scm b/guix/scripts/copy.scm
index 9ae204e6c6..624ef73e96 100644
--- a/guix/scripts/copy.scm
+++ b/guix/scripts/copy.scm
@@ -63,8 +63,8 @@ Throw an error on failure."
 
     (match (connect! session)
       ('ok
-       ;; Let the SSH agent authenticate us to the server.
-       (match (userauth-agent! session)
+       ;; Use public key authentication, via the SSH agent if it's available.
+       (match (userauth-public-key/auto! session)
          ('success
           session)
          (x
diff --git a/guix/scripts/environment.scm b/guix/scripts/environment.scm
index 1d3be6a84f..44f490043c 100644
--- a/guix/scripts/environment.scm
+++ b/guix/scripts/environment.scm
@@ -1,6 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014, 2015 David Thompson <davet@gnu.org>
-;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -60,12 +60,6 @@ directories in PROFILE, the store path of a profile."
 (define %default-shell
   (or (getenv "SHELL") "/bin/sh"))
 
-(define %network-configuration-files
-  '("/etc/resolv.conf"
-    "/etc/nsswitch.conf"
-    "/etc/services"
-    "/etc/hosts"))
-
 (define (purify-environment)
   "Unset almost all environment variables.  A small number of variables such
 as 'HOME' and 'USER' are left untouched."
@@ -408,21 +402,7 @@ host file systems to mount inside the container."
                      ;; When in Rome, do as Nix build.cc does: Automagically
                      ;; map common network configuration files.
                      (if network?
-                         (filter-map (lambda (file)
-                                       (and (file-exists? file)
-                                            (file-system-mapping
-                                             (source file)
-                                             (target file)
-                                             ;; XXX: On some GNU/Linux
-                                             ;; systems, /etc/resolv.conf is a
-                                             ;; symlink to a file in a tmpfs
-                                             ;; which, for an unknown reason,
-                                             ;; cannot be bind mounted
-                                             ;; read-only within the
-                                             ;; container.
-                                             (writable?
-                                              (string=? "/etc/resolv.conf")))))
-                                     %network-configuration-files)
+                         %network-file-mappings
                          '())
                      ;; Mappings for the union closure of all inputs.
                      (map (lambda (dir)
@@ -432,7 +412,8 @@ host file systems to mount inside the container."
                              (writable? #f)))
                           reqs)))
             (file-systems (append %container-file-systems
-                                  (map mapping->file-system mappings))))
+                                  (map file-system-mapping->bind-mount
+                                       mappings))))
        (exit/status
         (call-with-container file-systems
           (lambda ()
@@ -531,8 +512,10 @@ message if any test fails."
 
 (define (register-gc-root target root)
   "Make ROOT an indirect root to TARGET.  This is procedure is idempotent."
-  (let* ((root (string-append (canonicalize-path (dirname root))
-                              "/" root)))
+  (let* ((root (if (string-prefix? "/" root)
+                   root
+                   (string-append (canonicalize-path (dirname root))
+                                  "/" root))))
     (catch 'system-error
       (lambda ()
         (symlink target root)
diff --git a/guix/scripts/graph.scm b/guix/scripts/graph.scm
index 79ce503a2e..9804d41929 100644
--- a/guix/scripts/graph.scm
+++ b/guix/scripts/graph.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -21,12 +21,12 @@
   #:use-module (guix graph)
   #:use-module (guix grafts)
   #:use-module (guix scripts)
-  #:use-module (guix combinators)
   #:use-module (guix packages)
   #:use-module (guix monads)
   #:use-module (guix store)
   #:use-module (guix gexp)
   #:use-module (guix derivations)
+  #:use-module (guix memoization)
   #:use-module ((guix build-system gnu) #:select (standard-packages))
   #:use-module (gnu packages)
   #:use-module (guix sets)
@@ -191,12 +191,11 @@ Dependencies may include packages, origin, and file names."
                  %store-monad))))
 
 (define standard-package-set
-  (memoize
-   (lambda ()
-     "Return the set of standard packages provided by GNU-BUILD-SYSTEM."
-     (match (standard-packages)
-       (((labels packages . output) ...)
-        (list->setq packages))))))
+  (mlambda ()
+    "Return the set of standard packages provided by GNU-BUILD-SYSTEM."
+    (match (standard-packages)
+      (((labels packages . output) ...)
+       (list->setq packages)))))
 
 (define (bag-node-edges-sans-bootstrap thing)
   "Like 'bag-node-edges', but pretend that the standard packages of
diff --git a/guix/scripts/import.scm b/guix/scripts/import.scm
index 4d07e0fd69..8c2f705738 100644
--- a/guix/scripts/import.scm
+++ b/guix/scripts/import.scm
@@ -73,7 +73,8 @@ rather than \\n."
 ;;; Entry point.
 ;;;
 
-(define importers '("gnu" "nix" "pypi" "cpan" "hackage" "elpa" "gem" "cran" "crate"))
+(define importers '("gnu" "nix" "pypi" "cpan" "hackage" "stackage" "elpa" "gem"
+                    "cran" "crate"))
 
 (define (resolve-importer name)
   (let ((module (resolve-interface
diff --git a/guix/scripts/import/stackage.scm b/guix/scripts/import/stackage.scm
new file mode 100644
index 0000000000..cf47bff259
--- /dev/null
+++ b/guix/scripts/import/stackage.scm
@@ -0,0 +1,115 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 Federico Beffa <beffa@fbengineering.ch>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix scripts import stackage)
+  #:use-module (guix ui)
+  #:use-module (guix utils)
+  #:use-module (guix packages)
+  #:use-module (guix scripts)
+  #:use-module (guix import stackage)
+  #:use-module (guix scripts import)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-37)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 format)
+  #:export (guix-import-stackage))
+
+
+;;;
+;;; Command-line options.
+;;;
+
+(define %default-options
+  `((lts-version . "")
+    (include-test-dependencies? . #t)))
+
+(define (show-help)
+  (display (_ "Usage: guix import stackage PACKAGE-NAME
+Import and convert the LTS Stackage package for PACKAGE-NAME.\n"))
+  (display (_ "
+  -r VERSION, --lts-version=VERSION
+                               specify the LTS version to use"))
+  (display (_ "
+  -h, --help                   display this help and exit"))
+  (display (_ "
+  -t, --no-test-dependencies   don't include test-only dependencies"))
+  (display (_ "
+  -V, --version                display version information and exit"))
+  (newline)
+  (show-bug-report-information))
+
+(define %options
+  ;; Specification of the command-line options.
+  (cons* (option '(#\h "help") #f #f
+                 (lambda args
+                   (show-help)
+                   (exit 0)))
+         (option '(#\V "version") #f #f
+                 (lambda args
+                   (show-version-and-exit "guix import stackage")))
+         (option '(#\t "no-test-dependencies") #f #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'include-test-dependencies? #f
+                               (alist-delete 'include-test-dependencies?
+                                             result))))
+         (option '(#\r "lts-version") #t #f
+                 (lambda (opt name arg result)
+                   (alist-cons 'lts-version arg
+                               (alist-delete 'lts-version
+                                             result))))
+         %standard-import-options))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define (guix-import-stackage . args)
+  (define (parse-options)
+    ;; Return the alist of option values.
+    (args-fold* args %options
+                (lambda (opt name arg result)
+                  (leave (_ "~A: unrecognized option~%") name))
+                (lambda (arg result)
+                  (alist-cons 'argument arg result))
+                %default-options))
+
+  (let* ((opts (parse-options))
+         (args (filter-map (match-lambda
+                            (('argument . value)
+                             value)
+                            (_ #f))
+                           (reverse opts))))
+    (match args
+      ((package-name)
+       (let ((sexp (stackage->guix-package
+                    package-name
+                    #:include-test-dependencies?
+                    (assoc-ref opts 'include-test-dependencies?)
+                    #:lts-version (assoc-ref opts 'lts-version))))
+         (unless sexp
+           (leave (_ "failed to download cabal file for package '~a'~%")
+                  package-name))
+         sexp))
+      (()
+       (leave (_ "too few arguments~%")))
+      ((many ...)
+       (leave (_ "too many arguments~%"))))))
+
+;;; stackage.scm ends here
diff --git a/guix/scripts/lint.scm b/guix/scripts/lint.scm
index 9b991786c3..776e7332c5 100644
--- a/guix/scripts/lint.scm
+++ b/guix/scripts/lint.scm
@@ -1,7 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014 Cyril Roelandt <tipecaml@gmail.com>
 ;;; Copyright © 2014, 2015 Eric Bavier <bavier@member.fsf.org>
-;;; Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015, 2016 Mathieu Lirzin <mthl@gnu.org>
 ;;; Copyright © 2016 Danny Milosavljevic <dannym+a@scratchpost.org>
 ;;; Copyright © 2016 Hartmut Goebel <h.goebel@crazy-compilers.com>
@@ -32,7 +32,7 @@
   #:use-module (guix records)
   #:use-module (guix ui)
   #:use-module (guix utils)
-  #:use-module (guix combinators)
+  #:use-module (guix memoization)
   #:use-module (guix scripts)
   #:use-module (guix gnu-maintenance)
   #:use-module (guix monads)
@@ -90,9 +90,9 @@
   ;; provided MESSAGE.
   (let ((loc (or (package-field-location package field)
                  (package-location package))))
-    (format (guix-warning-port) "~a: ~a: ~a~%"
+    (format (guix-warning-port) "~a: ~a@~a: ~a~%"
             (location->string loc)
-            (package-full-name package)
+            (package-name package) (package-version package)
             message)))
 
 (define (call-with-accumulated-warnings thunk)
@@ -559,12 +559,11 @@ patch could not be found."
                       str)))
 
 (define official-gnu-packages*
-  (memoize
-   (lambda ()
-     "A memoizing version of 'official-gnu-packages' that returns the empty
+  (mlambda ()
+    "A memoizing version of 'official-gnu-packages' that returns the empty
 list when something goes wrong, such as a networking issue."
-     (let ((gnus (false-if-exception (official-gnu-packages))))
-       (or gnus '())))))
+    (let ((gnus (false-if-exception (official-gnu-packages))))
+      (or gnus '()))))
 
 (define (check-gnu-synopsis+description package)
   "Make sure that, if PACKAGE is a GNU package, it uses the synopsis and
@@ -959,12 +958,12 @@ or a list thereof")
 
 (define* (run-checkers package #:optional (checkers %checkers))
   "Run the given CHECKERS on PACKAGE."
-  (let ((tty? (isatty? (current-error-port)))
-        (name (package-full-name package)))
+  (let ((tty? (isatty? (current-error-port))))
     (for-each (lambda (checker)
                 (when tty?
-                  (format (current-error-port) "checking ~a [~a]...\x1b[K\r"
-                          name (lint-checker-name checker))
+                  (format (current-error-port) "checking ~a@~a [~a]...\x1b[K\r"
+                          (package-name package) (package-version package)
+                          (lint-checker-name checker))
                   (force-output (current-error-port)))
                 ((lint-checker-check checker) package))
               checkers)
diff --git a/guix/scripts/refresh.scm b/guix/scripts/refresh.scm
index 0dd7eee974..4d3c695aaf 100644
--- a/guix/scripts/refresh.scm
+++ b/guix/scripts/refresh.scm
@@ -205,6 +205,7 @@ unavailable optional dependencies such as Guile-JSON."
                  %elpa-updater
                  %cran-updater
                  %bioconductor-updater
+                 ((guix import stackage) => %stackage-updater)
                  %hackage-updater
                  ((guix import cpan) => %cpan-updater)
                  ((guix import pypi) => %pypi-updater)
diff --git a/guix/serialization.scm b/guix/serialization.scm
index 5953b84616..4cab5910f7 100644
--- a/guix/serialization.scm
+++ b/guix/serialization.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -30,7 +30,7 @@
   #:export (write-int read-int
             write-long-long read-long-long
             write-padding
-            write-string
+            write-bytevector write-string
             read-string read-latin1-string read-maybe-utf8-string
             write-string-list read-string-list
             write-string-pairs
@@ -102,15 +102,17 @@
         (or (zero? m)
             (put-bytevector p zero 0 (- 8 m)))))))
 
-(define (write-string s p)
-  (let* ((s (string->utf8 s))
-         (l (bytevector-length s))
+(define (write-bytevector s p)
+  (let* ((l (bytevector-length s))
          (m (modulo l 8))
          (b (make-bytevector (+ 8 l (if (zero? m) 0 (- 8 m))))))
     (bytevector-u32-set! b 0 l (endianness little))
     (bytevector-copy! s 0 b 8 l)
     (put-bytevector p b)))
 
+(define (write-string s p)
+  (write-bytevector (string->utf8 s) p))
+
 (define (read-byte-string p)
   (let* ((len (read-int p))
          (m   (modulo len 8))
diff --git a/guix/store.scm b/guix/store.scm
index 49549d0771..cce460f3ce 100644
--- a/guix/store.scm
+++ b/guix/store.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2012, 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -19,7 +19,7 @@
 (define-module (guix store)
   #:use-module (guix utils)
   #:use-module (guix config)
-  #:use-module (guix combinators)
+  #:use-module (guix memoization)
   #:use-module (guix serialization)
   #:use-module (guix monads)
   #:autoload   (guix base32) (bytevector->base32-string)
@@ -67,6 +67,7 @@
             query-path-hash
             hash-part->path
             query-path-info
+            add-data-to-store
             add-text-to-store
             add-to-store
             build-things
@@ -138,7 +139,7 @@
             direct-store-path
             log-file))
 
-(define %protocol-version #x10f)
+(define %protocol-version #x161)
 
 (define %worker-magic-1 #x6e697863)               ; "nixc"
 (define %worker-magic-2 #x6478696f)               ; "dxio"
@@ -266,12 +267,15 @@
     (path-info deriver hash refs registration-time nar-size)))
 
 (define-syntax write-arg
-  (syntax-rules (integer boolean string string-list string-pairs
+  (syntax-rules (integer boolean bytevector
+                 string string-list string-pairs
                  store-path store-path-list base16)
     ((_ integer arg p)
      (write-int arg p))
     ((_ boolean arg p)
      (write-int (if arg 1 0) p))
+    ((_ bytevector arg p)
+     (write-bytevector arg p))
     ((_ string arg p)
      (write-string arg p))
     ((_ string-list arg p)
@@ -537,14 +541,14 @@ encoding conversion errors."
                             #:key keep-failed? keep-going? fallback?
                             (verbosity 0)
                             rounds                ;number of build rounds
-                            (max-build-jobs 1)
+                            max-build-jobs
                             timeout
-                            (max-silent-time 3600)
+                            max-silent-time
                             (use-build-hook? #t)
                             (build-verbosity 0)
                             (log-type 0)
                             (print-build-trace #t)
-                            (build-cores (current-processor-count))
+                            build-cores
                             (use-substitutes? #t)
 
                             ;; Client-provided substitute URLs.  If it is #f,
@@ -570,21 +574,37 @@ encoding conversion errors."
                           ...)))))
     (write-int (operation-id set-options) socket)
     (send (boolean keep-failed?) (boolean keep-going?)
-          (boolean fallback?) (integer verbosity)
-          (integer max-build-jobs) (integer max-silent-time))
+          (boolean fallback?) (integer verbosity))
+    (when (< (nix-server-minor-version server) #x61)
+      (let ((max-build-jobs (or max-build-jobs 1))
+            (max-silent-time (or max-silent-time 3600)))
+        (send (integer max-build-jobs) (integer max-silent-time))))
     (when (>= (nix-server-minor-version server) 2)
       (send (boolean use-build-hook?)))
     (when (>= (nix-server-minor-version server) 4)
       (send (integer build-verbosity) (integer log-type)
             (boolean print-build-trace)))
-    (when (>= (nix-server-minor-version server) 6)
-      (send (integer build-cores)))
+    (when (and (>= (nix-server-minor-version server) 6)
+               (< (nix-server-minor-version server) #x61))
+      (let ((build-cores (or build-cores (current-processor-count))))
+        (send (integer build-cores))))
     (when (>= (nix-server-minor-version server) 10)
       (send (boolean use-substitutes?)))
     (when (>= (nix-server-minor-version server) 12)
       (let ((pairs `(,@(if timeout
                            `(("build-timeout" . ,(number->string timeout)))
                            '())
+                     ,@(if max-silent-time
+                           `(("build-max-silent-time"
+                              . ,(number->string max-silent-time)))
+                           '())
+                     ,@(if max-build-jobs
+                           `(("build-max-jobs"
+                              . ,(number->string max-build-jobs)))
+                           '())
+                     ,@(if build-cores
+                           `(("build-cores" . ,(number->string build-cores)))
+                           '())
                      ,@(if substitute-urls
                            `(("substitute-urls"
                               . ,(string-join substitute-urls)))
@@ -653,25 +673,31 @@ string).  Raise an error if no such path exists."
   "Return the info (hash, references, etc.) for PATH."
   path-info)
 
-(define add-text-to-store
+(define add-data-to-store
   ;; A memoizing version of `add-to-store', to avoid repeated RPCs with
   ;; the very same arguments during a given session.
   (let ((add-text-to-store
-         (operation (add-text-to-store (string name) (string text)
+         (operation (add-text-to-store (string name) (bytevector text)
                                        (string-list references))
                     #f
                     store-path)))
-    (lambda* (server name text #:optional (references '()))
-      "Add TEXT under file NAME in the store, and return its store path.
+    (lambda* (server name bytes #:optional (references '()))
+      "Add BYTES under file NAME in the store, and return its store path.
 REFERENCES is the list of store paths referred to by the resulting store
 path."
-      (let ((args  `(,text ,name ,references))
-            (cache (nix-server-add-text-to-store-cache server)))
+      (let* ((args  `(,bytes ,name ,references))
+             (cache (nix-server-add-text-to-store-cache server)))
         (or (hash-ref cache args)
-            (let ((path (add-text-to-store server name text references)))
+            (let ((path (add-text-to-store server name bytes references)))
               (hash-set! cache args path)
               path))))))
 
+(define* (add-text-to-store store name text #:optional (references '()))
+  "Add TEXT under file NAME in the store, and return its store path.
+REFERENCES is the list of store paths referred to by the resulting store
+path."
+  (add-data-to-store store name (string->utf8 text) references))
+
 (define true
   ;; Define it once and for all since we use it as a default value for
   ;; 'add-to-store' and want to make sure two default values are 'eq?' for the
@@ -1266,11 +1292,10 @@ valid inputs."
 (define store-regexp*
   ;; The substituter makes repeated calls to 'store-path-hash-part', hence
   ;; this optimization.
-  (memoize
-   (lambda (store)
-     "Return a regexp matching a file in STORE."
-     (make-regexp (string-append "^" (regexp-quote store)
-                                 "/([0-9a-df-np-sv-z]{32})-([^/]+)$")))))
+  (mlambda (store)
+    "Return a regexp matching a file in STORE."
+    (make-regexp (string-append "^" (regexp-quote store)
+                                "/([0-9a-df-np-sv-z]{32})-([^/]+)$"))))
 
 (define (store-path-package-name path)
   "Return the package name part of PATH, a file name in the store."
diff --git a/guix/ui.scm b/guix/ui.scm
index 7d4c437354..6247944068 100644
--- a/guix/ui.scm
+++ b/guix/ui.scm
@@ -332,39 +332,39 @@ Report bugs to: ~a.") %guix-bug-report-address)
 General help using GNU software: <http://www.gnu.org/gethelp/>"))
   (newline))
 
+(define (augmented-system-error-handler file)
+  "Return a 'system-error' handler that mentions FILE in its message."
+  (lambda (key proc fmt args errno)
+    ;; Augment the FMT and ARGS with information about TARGET (this
+    ;; information is missing as of Guile 2.0.11, making the exception
+    ;; uninformative.)
+    (apply throw key proc "~A: ~S"
+           (list (strerror (car errno)) file)
+           (list errno))))
+
+(define-syntax-rule (error-reporting-wrapper proc (args ...) file)
+  "Wrap PROC such that its 'system-error' exceptions are augmented to mention
+FILE."
+  (let ((real-proc (@ (guile) proc)))
+    (lambda (args ...)
+      (catch 'system-error
+        (lambda ()
+          (real-proc args ...))
+        (augmented-system-error-handler file)))))
+
 (set! symlink
   ;; We 'set!' the global binding because (gnu build ...) modules and similar
   ;; typically don't use (guix ui).
-  (let ((real-symlink (@ (guile) symlink)))
-    (lambda (target link)
-      "This is a 'symlink' replacement that provides proper error reporting."
-      (catch 'system-error
-        (lambda ()
-          (real-symlink target link))
-        (lambda (key proc fmt args errno)
-          ;; Augment the FMT and ARGS with information about LINK (this
-          ;; information is missing as of Guile 2.0.11, making the exception
-          ;; uninformative.)
-          (apply throw key proc "~A: ~S"
-                 (list (strerror (car errno)) link)
-                 (list errno)))))))
+  (error-reporting-wrapper symlink (source target) target))
 
 (set! copy-file
   ;; Note: here we use 'set!', not #:replace, because UIs typically use
   ;; 'copy-recursively', which doesn't use (guix ui).
-  (let ((real-copy-file (@ (guile) copy-file)))
-    (lambda (source target)
-      "This is a 'copy-file' replacement that provides proper error reporting."
-      (catch 'system-error
-        (lambda ()
-          (real-copy-file source target))
-        (lambda (key proc fmt args errno)
-          ;; Augment the FMT and ARGS with information about TARGET (this
-          ;; information is missing as of Guile 2.0.11, making the exception
-          ;; uninformative.)
-          (apply throw key proc "~A: ~S"
-                 (list (strerror (car errno)) target)
-                 (list errno)))))))
+  (error-reporting-wrapper copy-file (source target) target))
+
+(set! canonicalize-path
+  (error-reporting-wrapper canonicalize-path (file) file))
+
 
 (define (make-regexp* regexp . flags)
   "Like 'make-regexp' but error out if REGEXP is invalid, reporting the error
diff --git a/guix/utils.scm b/guix/utils.scm
index ee06e47fe9..72dc0687a4 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -33,7 +33,7 @@
   #:use-module (ice-9 binary-ports)
   #:autoload   (rnrs io ports) (make-custom-binary-input-port)
   #:use-module ((rnrs bytevectors) #:select (bytevector-u8-set!))
-  #:use-module (guix combinators)
+  #:use-module (guix memoization)
   #:use-module ((guix build utils) #:select (dump-port))
   #:use-module ((guix build syscalls) #:select (mkdtemp! fdatasync))
   #:use-module (ice-9 vlist)
@@ -771,11 +771,10 @@ be determined."
   (column        location-column))                ; 0-indexed column
 
 (define location
-  (memoize
-   (lambda (file line column)
-     "Return the <location> object for the given FILE, LINE, and COLUMN."
-     (and line column file
-          (make-location file line column)))))
+  (mlambda (file line column)
+    "Return the <location> object for the given FILE, LINE, and COLUMN."
+    (and line column file
+         (make-location file line column))))
 
 (define (source-properties->location loc)
   "Return a location object based on the info in LOC, an alist as returned