From b46f34452e9dec50eee6ddbe07875f05e421a81c Mon Sep 17 00:00:00 2001 From: Khem Raj Date: Wed, 11 Jun 2025 20:22:08 -0700 Subject: [PATCH] libunwind: Do not use __attribute__((target("gcs"))) with non-clang compilers (#138077) 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 --- libunwind/src/UnwindLevel1.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/libunwind/src/UnwindLevel1.c b/libunwind/src/UnwindLevel1.c index a258a832a9c3..f3b451ad9b73 100644 --- a/libunwind/src/UnwindLevel1.c +++ b/libunwind/src/UnwindLevel1.c @@ -188,10 +188,11 @@ extern int __unw_step_stage2(unw_cursor_t *); #if defined(_LIBUNWIND_USE_GCS) // Enable the GCS target feature to permit gcspop instructions to be used. -__attribute__((target("gcs"))) +__attribute__((target("+gcs"))) #endif static _Unwind_Reason_Code -unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) { +unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, + _Unwind_Exception *exception_object) { __unw_init_local(cursor, uc); _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_obj=%p)", @@ -332,12 +333,12 @@ unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *except #if defined(_LIBUNWIND_USE_GCS) // Enable the GCS target feature to permit gcspop instructions to be used. -__attribute__((target("gcs"))) +__attribute__((target("+gcs"))) #endif static _Unwind_Reason_Code unwind_phase2_forced(unw_context_t *uc, unw_cursor_t *cursor, - _Unwind_Exception *exception_object, - _Unwind_Stop_Fn stop, void *stop_parameter) { + _Unwind_Exception *exception_object, _Unwind_Stop_Fn stop, + void *stop_parameter) { __unw_init_local(cursor, uc); // uc is initialized by __unw_getcontext in the parent frame. The first stack @@ -443,7 +444,6 @@ unwind_phase2_forced(unw_context_t *uc, unw_cursor_t *cursor, return _URC_FATAL_PHASE2_ERROR; } - /// Called by __cxa_throw. Only returns if there is a fatal error. _LIBUNWIND_EXPORT _Unwind_Reason_Code _Unwind_RaiseException(_Unwind_Exception *exception_object) {