gnu: Default to GCC 5.

This reinstates and adjusts
commit e3d0fcbf7e55e8cbe8d0a1c5a24d73f341d7243b.

* gnu/packages/patches/gcc-libiberty-printf-decl.patch: New file.
* gnu/packages/gcc.scm (gcc-5)[source]: Use it.
[patches]: Add "gcc-arm-bug-71399.patch".
(gcc): Switch to GCC-5.
* gnu/packages/commencement.scm (libstdc++-boot0): New variable.
(gcc-boot0)[inputs]: Add it.
(gcc-toolchain-4.9): Switch to GCC-4.9.
(gcc-toolchain-5): Switch to GCC-FINAL.
* gnu/local.mk (dist_patch_DATA): Add 'gcc-libiberty-printf-decl.patch'.

1 files changed, 25 insertions, 2 deletions

diff --git a/gnu/packages/commencement.scm b/gnu/packages/commencement.scm
index 2431babcad..1238f5cf5b 100644
--- a/gnu/packages/commencement.scm
+++ b/gnu/packages/commencement.scm
@@ -172,6 +172,26 @@
                     ,cf)))))
      (inputs %boot0-inputs))))
 
+(define libstdc++-boot0
+  ;; GCC's libcc1 is always built as a shared library (the top-level
+  ;; 'Makefile.def' forcefully adds --enable-shared) and thus needs to refer
+  ;; to libstdc++.so.  We cannot build libstdc++-5.3 because it relies on
+  ;; C++14 features missing in our bootstrap compiler.
+  (let ((lib (package-with-bootstrap-guile (make-libstdc++ gcc-4.9))))
+    (package
+      (inherit lib)
+      (name "libstdc++-boot0")
+      (arguments
+       `(#:guile ,%bootstrap-guile
+         #:implicit-inputs? #f
+
+         ;; XXX: libstdc++.so NEEDs ld.so for some reason.
+         #:validate-runpath? #f
+
+         ,@(package-arguments lib)))
+      (inputs %boot0-inputs)
+      (native-inputs '()))))
+
 (define gcc-boot0
   (package-with-bootstrap-guile
    (package (inherit gcc)
@@ -257,6 +277,9 @@
                ("mpc-source" ,(package-source mpc))
                ("binutils-cross" ,binutils-boot0)
 
+               ;; The libstdc++ that libcc1 links against.
+               ("libstdc++" ,libstdc++-boot0)
+
                ;; Call it differently so that the builder can check whether
                ;; the "libc" input is #f.
                ("libc-native" ,@(assoc-ref %boot0-inputs "libc"))
@@ -986,10 +1009,10 @@ and binaries, plus debugging symbols in the 'debug' output), and Binutils.")
   (gcc-toolchain gcc-4.8))
 
 (define-public gcc-toolchain-4.9
-  (gcc-toolchain gcc-final))
+  (gcc-toolchain gcc-4.9))
 
 (define-public gcc-toolchain-5
-  (gcc-toolchain gcc-5))
+  (gcc-toolchain gcc-final))
 
 (define-public gcc-toolchain-6
   (gcc-toolchain gcc-6))