commit 062cfada643c1aa48a1bb81894e2920d390fe8cf
author Fangrui Song <i@maskray.me> Tue Feb 27 16:32:53 2024 -0800
committer GitHub <noreply@github.com> Tue Feb 27 16:32:53 2024 -0800
tree c614265ec4b33ffeb05a33e73af77506e249110d
parent d699d9d609a24d80809df15efe47ac539da90e93

[builtins] Disable COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY by default (#83201)

Most of GCC's Linux targets have a link spec
`%{!static|static-pie:--eh-frame-hdr}` that doesn't pass --eh-frame-hdr
for `-static` links. `-static` links are supposed to utilize
`__register_frame_info` (called by `crtbeginT.o`, not by crtbegin.o or
crtbeginS.o) as a replacement.

compiler-rt crtbegin (not used with GCC) has some ehframe code, which is
not utilized because Clang driver unconditionally passes --eh-frame-hdr
for Linux targets, even for -static. In addition, LLVM libunwind
implements `__register_frame_info` as an empty stub.

Furthermore, in a non-static link, the `__register_frame_info`
references can cause an undesired weak dynamic symbol.

For now, just disable the config by default.

compiler-rt/lib/builtins/CMakeLists.txt

diff --git a/compiler-rt/lib/builtins/CMakeLists.txt b/compiler-rt/lib/builtins/CMakeLists.txt
index 28ded87..83f7697 100644
--- a/compiler-rt/lib/builtins/CMakeLists.txt
+++ b/compiler-rt/lib/builtins/CMakeLists.txt
@@ -916,7 +916,7 @@
 if (COMPILER_RT_BUILD_CRT)
   add_compiler_rt_component(crt)
 
-  option(COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY "Use eh_frame in crtbegin.o/crtend.o" ON)
+  option(COMPILER_RT_CRT_USE_EH_FRAME_REGISTRY "Use eh_frame in crtbegin.o/crtend.o" OFF)
 
   include(CheckSectionExists)
   check_section_exists(".init_array" COMPILER_RT_HAS_INITFINI_ARRAY

compiler-rt/test/builtins/Unit/ctor_dtor.c

diff --git a/compiler-rt/test/builtins/Unit/ctor_dtor.c b/compiler-rt/test/builtins/Unit/ctor_dtor.c
index 4756072..3d5f895 100644
--- a/compiler-rt/test/builtins/Unit/ctor_dtor.c
+++ b/compiler-rt/test/builtins/Unit/ctor_dtor.c
@@ -9,23 +9,13 @@
 
 // Ensure the various startup functions are called in the proper order.
 
-// CHECK: __register_frame_info()
 /// ctor() is here if ld.so/libc supports DT_INIT/DT_FINI
 // CHECK:      main()
 /// dtor() is here if ld.so/libc supports DT_INIT/DT_FINI
-// CHECK:      __deregister_frame_info()
 
 struct object;
 static int counter;
 
-void __register_frame_info(const void *fi, struct object *obj) {
-  printf("__register_frame_info()\n");
-}
-
-void __deregister_frame_info(const void *fi) {
-  printf("__deregister_frame_info()\n");
-}
-
 void __attribute__((constructor)) ctor() {
   printf("ctor()\n");
   ++counter;