https://github.com/kraj created https://github.com/llvm/llvm-project/pull/138077
…compilers
This attribute is unsupported in GCC, so far it worked because before GCC15 did
not define this macros in _CHKFEAT_GCS in arm_acle.h [1]
With gcc15 compiler libunwind's check for this macros is succeeding and it ends
up enabling 'gcs' by using function attribute, this works with clang but not
with gcc.
We can see this in rust compiler bootstrap for aarch64/musl when system uses
gcc15, it ends up with these errors
Building libunwind.a for aarch64-poky-linux-musl
cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:191:1:
error: arch extension 'gcs' should be prefixed by '+' cargo:warning= 191 |
unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception
*exception_object) {
cargo:warning= | ^~~~~~~~~~~~~
cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:337:22:
error: arch extension 'gcs' should be prefixed by '+'
cargo:warning= 337 | _Unwind_Stop_Fn stop, void
*stop_parameter) {
cargo:warning= | ^~~~~~~~~~~~~~~
[1] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=5a6af707f0af
>From 13d2bffa06845d9c2005e9d3871632a88a17d0d9 Mon Sep 17 00:00:00 2001
From: Khem Raj <raj.k...@gmail.com>
Date: Wed, 30 Apr 2025 19:51:19 -0700
Subject: [PATCH] libunwind: Do not use __attribute__((target("gcs"))) with
non-clang compilers
This attribute is unsupported in GCC, so far it worked because before GCC15
did not define this macros in _CHKFEAT_GCS in arm_acle.h [1]
With gcc15 compiler libunwind's check for this macros is succeeding and it
ends up enabling 'gcs' by using function attribute, this works with clang
but not with gcc.
We can see this in rust compiler bootstrap for aarch64/musl when system
uses gcc15, it ends up with these errors
Building libunwind.a for aarch64-poky-linux-musl
cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:191:1:
error: arch extension 'gcs' should be prefixed by '+'
cargo:warning= 191 | unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor,
_Unwind_Exception *exception_object) {
cargo:warning= | ^~~~~~~~~~~~~
cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:337:22:
error: arch extension 'gcs' should be prefixed by '+'
cargo:warning= 337 | _Unwind_Stop_Fn stop, void
*stop_parameter) {
cargo:warning= | ^~~~~~~~~~~~~~~
[1] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=5a6af707f0af
Signed-off-by: Khem Raj <raj.k...@gmail.com>
---
libunwind/src/UnwindLevel1.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libunwind/src/UnwindLevel1.c b/libunwind/src/UnwindLevel1.c
index a258a832a9c31..4771632c49c31 100644
--- a/libunwind/src/UnwindLevel1.c
+++ b/libunwind/src/UnwindLevel1.c
@@ -186,7 +186,7 @@ unwind_phase1(unw_context_t *uc, unw_cursor_t *cursor,
_Unwind_Exception *except
}
extern int __unw_step_stage2(unw_cursor_t *);
-#if defined(_LIBUNWIND_USE_GCS)
+#if defined(_LIBUNWIND_USE_GCS) && defined(__clang__)
// Enable the GCS target feature to permit gcspop instructions to be used.
__attribute__((target("gcs")))
#endif
@@ -330,7 +330,7 @@ unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor,
_Unwind_Exception *except
return _URC_FATAL_PHASE2_ERROR;
}
-#if defined(_LIBUNWIND_USE_GCS)
+#if defined(_LIBUNWIND_USE_GCS) && defined(__clang__)
// Enable the GCS target feature to permit gcspop instructions to be used.
__attribute__((target("gcs")))
#endif
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