bug#37509: [core-updates] [PATCH] gnu: gcc: Fix mingw cross compiler.

[Jan Nieuwenhuizen <jan.nieuwenhuizen@verum.com>]

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Running

    ./pre-inst-env guix build --target=x86_64-w64-mingw32 hello

on core-updates fails with

--8<---------------cut here---------------start------------->8---
../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc: In function ‘void* __gnu_cxx::aligned_alloc(std::size_t, std::size_t)’:
../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc:78:10: error: ‘memalign’ was not declared in this scope
   return memalign (al, sz);
          ^~~~~~~~
../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc:78:10: note: suggested alternative: ‘max_align_t’
   return memalign (al, sz);
          ^~~~~~~~
          max_align_t
--8<---------------cut here---------------end--------------->8---

The attached patch fixes this and produces a working cross-built hello.

The weird thing is that I looked at Debian's mingw cross compilers and
its mingw-w64 package and cannot seem to find anything that resembles
this build problem or a fix.

Greetings,
janneke


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From 4966d8dc9e079a5fb776f456dfb3f0918bcfa1b9 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Tue, 24 Sep 2019 20:23:31 +0200
Subject: [PATCH] gnu: gcc: Fix mingw cross compiler.

* gnu/packages/patches/gcc-7-cross-mingw.patch: New file.
* gnu/packages/cross-base.scm (cross-gcc): Use it for target mingw and gcc >= 7.
* gnu/local.mk (dist_patch_DATA): Add it.
---
 gnu/local.mk                                 |  1 +
 gnu/packages/cross-base.scm                  |  6 ++++-
 gnu/packages/patches/gcc-7-cross-mingw.patch | 24 ++++++++++++++++++++
 3 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 gnu/packages/patches/gcc-7-cross-mingw.patch

diff --git a/gnu/local.mk b/gnu/local.mk
index 5705494090..a7b1c65e82 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -851,6 +851,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gcc-6-cross-environment-variables.patch	\
   %D%/packages/patches/gcc-6-source-date-epoch-1.patch		\
   %D%/packages/patches/gcc-6-source-date-epoch-2.patch		\
+  %D%/packages/patches/gcc-7-cross-mingw.patch			\
   %D%/packages/patches/gcc-8-cross-environment-variables.patch	\
   %D%/packages/patches/gcc-8-strmov-store-file-names.patch	\
   %D%/packages/patches/gcc-9-asan-fix-limits-include.patch	\
diff --git a/gnu/packages/cross-base.scm b/gnu/packages/cross-base.scm
index 78dae7431a..36f2f5961f 100644
--- a/gnu/packages/cross-base.scm
+++ b/gnu/packages/cross-base.scm
@@ -229,7 +229,11 @@ target that libc."
                        ((version>=? (package-version xgcc) "8.0") (search-patch "gcc-8-cross-environment-variables.patch"))
                        ((version>=? (package-version xgcc) "6.0") (search-patch "gcc-6-cross-environment-variables.patch"))
                        (else  (search-patch "gcc-cross-environment-variables.patch")))
-                      (cross-gcc-patches target))))
+                      (cross-gcc-patches target))
+                (if (and (target-mingw? target)
+                         (version>=? (package-version xgcc) "7.0"))
+                    (search-patches "gcc-7-cross-mingw.patch")
+                    '())))
               (modules '((guix build utils)))
               (snippet
                (cross-gcc-snippet target))))
diff --git a/gnu/packages/patches/gcc-7-cross-mingw.patch b/gnu/packages/patches/gcc-7-cross-mingw.patch
new file mode 100644
index 0000000000..eec6f88953
--- /dev/null
+++ b/gnu/packages/patches/gcc-7-cross-mingw.patch
@@ -0,0 +1,24 @@
+This fixes
+
+../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc: In function ‘void* __gnu_cxx::aligned_alloc(std::size_t, std::size_t)’:
+../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc:78:10: error: ‘memalign’ was not declared in this scope
+   return memalign (al, sz);
+          ^~~~~~~~
+../../../../gcc-7.4.0/libstdc++-v3/libsupc++/new_opa.cc:78:10: note: suggested alternative: ‘max_align_t’
+   return memalign (al, sz);
+          ^~~~~~~~
+          max_align_t
+
+diff --git a/libstdc++-v3/libsupc++/new_opa.cc b/libstdc++-v3/libsupc++/new_opa.cc
+index 94e79cadb0e..084900e0daf 100644
+--- a/libstdc++-v3/libsupc++/new_opa.cc
++++ b/libstdc++-v3/libsupc++/new_opa.cc
+@@ -39,6 +39,8 @@ extern "C" void *memalign(std::size_t boundary, std::size_t size);
+ # endif
+ #endif
+ 
++#define memalign _aligned_malloc
++
+ using std::new_handler;
+ using std::bad_alloc;
+ 
-- 
2.23.0


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-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
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