Make _LIBUNWIND_SUPPORT_FRAME_APIS a build-time option

Sterling-Augustine · Sterling-Augustine · commit 5eb44df1b64d · 2023-08-23T14:34:40.000-07:00
Previously this was based on target architecture, but that makes very little sense--frame API availability is generally for libgcc compatibility and that is dependent on runtime needs rather than target architecture. Default this to on, so as not to remove the apis from environments that already have them. The functions this macro protects are stubs for libgcc-compatibility. Today, libunwind as a drop-in replacement for libgcc_eh links on x86, x86_64, and powerpc, but not aarch64, which doesn't really make sense. As there is nothing architecture specific about these, they should be provided everywhere or nowhere. The target-specific protection goes all the way back to the original code contribution in 312fcd0 from 2013, so the original reason is lost to history, and probably not relevant today. Differential Revision: https://reviews.llvm.org/D158011
diff --git a/libunwind/CMakeLists.txt b/libunwind/CMakeLists.txt
@@ -51,6 +51,7 @@ option(LIBUNWIND_IS_BAREMETAL "Build libunwind for baremetal targets." OFF)
 option(LIBUNWIND_USE_FRAME_HEADER_CACHE "Cache frame headers for unwinding. Requires locking dl_iterate_phdr." OFF)
 option(LIBUNWIND_REMEMBER_HEAP_ALLOC "Use heap instead of the stack for .cfi_remember_state." OFF)
 option(LIBUNWIND_INSTALL_HEADERS "Install the libunwind headers." ON)
+option(LIBUNWIND_ENABLE_FRAME_APIS "Include libgcc-compatible frame apis." OFF)
 
 set(LIBUNWIND_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING
     "Define suffix of library directory name (32/64)")
@@ -250,6 +251,11 @@ if (NOT LIBUNWIND_ENABLE_CROSS_UNWINDING)
   add_compile_flags(-D_LIBUNWIND_IS_NATIVE_ONLY)
 endif()
 
+# Include stubs for __register_frame_info_bases and related
+if (LIBUNWIND_ENABLE_FRAME_APIS)
+  add_compile_flags(-D_LIBUNWIND_SUPPORT_FRAME_APIS)
+endif()
+
 # Threading-support
 if (NOT LIBUNWIND_ENABLE_THREADS)
   add_compile_flags(-D_LIBUNWIND_HAS_NO_THREADS)
diff --git a/libunwind/src/config.h b/libunwind/src/config.h
@@ -108,10 +108,6 @@
 #define _LIBUNWIND_BUILD_SJLJ_APIS
 #endif
 
-#if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__)
-#define _LIBUNWIND_SUPPORT_FRAME_APIS
-#endif
-
 #if defined(__i386__) || defined(__x86_64__) || defined(__powerpc__) ||        \
     (!defined(__APPLE__) && defined(__arm__)) || defined(__aarch64__) ||       \
     defined(__mips__) || defined(__riscv) || defined(__hexagon__) ||           \
