gnu: gcc-11: Fix build on powerpc64le.

* gnu/packages/patches/gcc-11-libstdc++-powerpc.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register patch.
* gnu/packages/gcc.scm (make-libstdc++): Apply patch for gcc versions >= 11
and < 12 on ppc64le.

Co-authored-by: Christopher Baines <mail@cbaines.net>
Signed-off-by: Christopher Baines <mail@cbaines.net>

3 files changed, 39 insertions, 2 deletions

diff --git a/gnu/local.mk b/gnu/local.mk
index b07811f1cb..1255846462 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -1184,6 +1184,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gcc-11-libstdc++-hurd-libpthread.patch   \
   %D%/packages/patches/gcc-12-cross-environment-variables.patch \
   %D%/packages/patches/gcc-10-tree-sra-union-handling.patch	\
+  %D%/packages/patches/gcc-11-libstdc++-powerpc.patch           \
   %D%/packages/patches/gcolor3-update-libportal-usage.patch	\
   %D%/packages/patches/gd-fix-tests-on-i686.patch		\
   %D%/packages/patches/gd-brect-bounds.patch			\
diff --git a/gnu/packages/gcc.scm b/gnu/packages/gcc.scm
index a511cdbc45..5b1ef83ce6 100644
--- a/gnu/packages/gcc.scm
+++ b/gnu/packages/gcc.scm
@@ -2,7 +2,7 @@
 ;;; Copyright © 2012-2023 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2014, 2015, 2018 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2014, 2015, 2016, 2017, 2019, 2021 Ricardo Wurmus <rekado@elephly.net>
-;;; Copyright © 2015 Andreas Enge <andreas@enge.fr>
+;;; Copyright © 2015, 2023 Andreas Enge <andreas@enge.fr>
 ;;; Copyright © 2015-2018, 2020-2023 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2016 Carlos Sánchez de La Lama <csanchezdll@gmail.com>
 ;;; Copyright © 2018 Tobias Geerinckx-Rice <me@tobias.gr>
@@ -889,6 +889,15 @@ using compilers other than GCC."
                                           ":")
                                          "\nAM_CXXFLAGS = ")))))))
                '())
+         ,@(let ((version (package-version gcc)))
+                (if (and (target-ppc64le?)
+                    (version>=? version "11")
+                    (not (version>=? version "12")))
+               `((add-after 'unpack 'patch-powerpc
+                   (lambda* (#:key inputs #:allow-other-keys)
+                     (invoke "patch" "--force" "-p1" "-i"
+                             (assoc-ref inputs "powerpc64le-patch")))))
+               '()))
          ;; Force rs6000 (i.e., powerpc) libdir to be /lib and not /lib64.
          (add-before 'chdir 'fix-rs6000-libdir
            (lambda _
@@ -905,7 +914,14 @@ using compilers other than GCC."
                                            "/include"))))
     (outputs '("out" "debug"))
     (inputs '())
-    (native-inputs '())
+    (native-inputs
+     `(,@(if (and (target-ppc64le?)
+                  (let ((version (package-version gcc)))
+                    (and
+                     (version>=? version "11")
+                     (not (version>=? version "12")))))
+             `(("powerpc64le-patch" ,(search-patch "gcc-11-libstdc++-powerpc.patch")))
+             '())))
     (propagated-inputs '())
     (synopsis "GNU C++ standard library")))
 
diff --git a/gnu/packages/patches/gcc-11-libstdc++-powerpc.patch b/gnu/packages/patches/gcc-11-libstdc++-powerpc.patch
new file mode 100644
index 0000000000..c0b96c3bc8
--- /dev/null
+++ b/gnu/packages/patches/gcc-11-libstdc++-powerpc.patch
@@ -0,0 +1,20 @@
+--- a/libstdc++-v3/src/c++17/floating_from_chars.cc
++++ b/libstdc++-v3/src/c++17/floating_from_chars.cc
+@@ -495,10 +495,16 @@
+ from_chars(const char* first, const char* last, __ieee128& value,
+          chars_format fmt) noexcept
+ {
++  errc ec = errc::invalid_argument;
++#if _GLIBCXX_USE_CXX11_ABI
+   buffer_resource mr;
+   pmr::string buf(&mr);
++#else
++  string buf;
++  if (!reserve_string(buf))
++    return make_result(first, 0, {}, ec);
++#endif
+   size_t len = 0;
+-  errc ec = errc::invalid_argument;
+   __try
+     {
+       if (const char* pat = pattern(first, last, fmt, buf)) [[likely]]