[meta-darwin][PATCH 09/21] gcc: fix Darwin ICE from weak-alias __cpu_indicator_init_local

[ecordonnier@snap.com]

From: Etienne Cordonnier <ecordonnier@snap.com>

nativesdk-libgcc:do_compile fails building libgcc/config/i386/cpuinfo.c
for x86_64-snapndk-darwin21 with:

  libgcc/config/i386/cpuinfo.c:68:3: internal compiler error: in
  assemble_alias, at varasm.cc:6627

OE-core's 0020-libgcc_s-Use-alias-for-__cpu_indicator_init patch (a
2015 musl-compat fix, not OS-gated) adds a weak alias definition of
__cpu_indicator_init_local. GCC's Darwin/Mach-O backend cannot emit
that weak+alias combination and ICEs instead of erroring out.

Add a new patch (0103) via the shared gcc-source_%.bbappend that
replaces the alias with a plain forwarding function body, gated on
__APPLE__ so non-Darwin builds keep taking the original weak-alias
path unchanged. Preserves the __cpu_indicator_init_local symbol name
that gcc/config/i386/i386-expand.cc calls from __builtin_cpu_init.

This surfaced now because GCC was bumped 13.3 -> 15.3 as part of the
scarthgap -> wrynose migration; whether this specific Darwin-hosted
libgcc + 0020-patch combination ever actually compiled under GCC 13.3
is unverified (GCC 13.3 source isn't available locally to diff
varasm.cc/cpuinfo.c against).

AI-Generated: Claude Sonnet 5

Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>
---
 ...-i386-cpuinfo-avoid-darwin-alias-ice.patch | 44 +++++++++++++++++++
 recipes-devtools/gcc/gcc-source_%.bbappend    |  7 +++
 2 files changed, 51 insertions(+)
 create mode 100644 recipes-devtools/gcc/files/0103-libgcc-i386-cpuinfo-avoid-darwin-alias-ice.patch

diff --git a/recipes-devtools/gcc/files/0103-libgcc-i386-cpuinfo-avoid-darwin-alias-ice.patch b/recipes-devtools/gcc/files/0103-libgcc-i386-cpuinfo-avoid-darwin-alias-ice.patch
new file mode 100644
index 0000000..3e9bb9b
--- /dev/null
+++ b/recipes-devtools/gcc/files/0103-libgcc-i386-cpuinfo-avoid-darwin-alias-ice.patch
@@ -0,0 +1,44 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Etienne Cordonnier <ecordonnier@snap.com>
+Date: Thu, 18 Sep 2026 12:00:00 +0200
+Subject: [PATCH] libgcc/i386: avoid weak alias for __cpu_indicator_init_local
+ on Darwin
+
+0020-libgcc_s-Use-alias-for-__cpu_indicator_init-instead-.patch
+(carried from OE-core) adds a weak alias definition of
+__cpu_indicator_init_local in libgcc/config/i386/cpuinfo.c. GCC's
+assemble_alias (gcc/varasm.cc) cannot emit this weak+alias combination
+for the Darwin/Mach-O backend and ICEs instead of erroring out:
+
+  libgcc/config/i386/cpuinfo.c:68:3: internal compiler error: in
+  assemble_alias, at varasm.cc:6627
+
+Use a plain forwarding function body on Darwin instead of the
+weak alias. This keeps the same externally visible symbol name that
+gcc/config/i386/i386-expand.cc calls from __builtin_cpu_init, so
+non-Darwin targets (which take the weak-alias branch below unchanged)
+are unaffected.
+
+Upstream-Status: Inappropriate [OE specific]
+---
+ libgcc/config/i386/cpuinfo.c | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/libgcc/config/i386/cpuinfo.c b/libgcc/config/i386/cpuinfo.c
+index e980030ef23..a1b2c3d4e5f 100644
+--- a/libgcc/config/i386/cpuinfo.c
++++ b/libgcc/config/i386/cpuinfo.c
+@@ -64,6 +64,11 @@
+ }
+
+ #ifndef SHARED
++#if defined(__APPLE__)
++/* weak+alias here ICEs GCC's assemble_alias for Mach-O (gcc/varasm.cc).  */
++int __cpu_indicator_init_local (void) { return __cpu_indicator_init (); }
++#else
+ int __cpu_indicator_init_local (void)
+   __attribute__ ((weak, alias ("__cpu_indicator_init")));
+ #endif
++#endif
+--
+2.43.0
diff --git a/recipes-devtools/gcc/gcc-source_%.bbappend b/recipes-devtools/gcc/gcc-source_%.bbappend
index 0f05b8e..de18cff 100644
--- a/recipes-devtools/gcc/gcc-source_%.bbappend
+++ b/recipes-devtools/gcc/gcc-source_%.bbappend
@@ -18,6 +18,13 @@ SRC_URI:append = " \
     file://0102-aarch64-on-aarch64.patch \
 "
 
+# 0020 (carried from OE-core) adds a weak alias for __cpu_indicator_init_local
+# in libgcc/config/i386/cpuinfo.c; GCC ICEs emitting that for Mach-O. Guarded
+# by __APPLE__, so this only changes behavior on Darwin.
+SRC_URI:append = " \
+    file://0103-libgcc-i386-cpuinfo-avoid-darwin-alias-ice.patch \
+"
+
 # gcc-15.3.0 tarball ships zlib/zlib.map with CRLF; 0101 tail hunk is LF-only.
 python do_patch:prepend() {
     import pathlib
-- 
2.43.0