[libunwind] Remove the legacy Unwind_AppleExtras.cpp

[ldionne]

Summary

Unwind_AppleExtras.cpp contained annotations telling the linker that
some symbols are not available on some very old platforms. However,
those platforms are not supported anymore, so the annotations are not
used.

Why remove this? In addition to cleaning up the code base, this also
removes the possibility of implementing those annotations incorrectly
(which was the case previously), which could lead to important symbols
being hidden when they should have been visible.

[ldionne]

libunwind/src/Unwind_AppleExtras.cpp

63–82

I am very confident this isn't useful anymore.

88–94

These ones I have a bit more doubt. I think either we don't care about hiding those anymore, or we do but in that case the current annotations are out of date, since they only hide the symbols for os10.4, os10.5 and os10.6, which is far from the only "os"es released by Apple.

106–119

I am very confident this isn't useful anymore.

[al45tair]

Agree with Louis; these symbols aren’t hidden on newer systems as we haven’t kept this up to date, so removing it seems sensible.

[MaskRay]

Rubber stamp from #libunwind

[steven_wu]

I am pretty sure if they are not useful anymore. Those symbols are only useful for back-deployment (linking application to system libunwind). Even if someone decides to build libunwind for 10.4, they don't need those symbols as long as they link their application against the newly built libunwind.

[ldionne]

The CI is passing modulo some unrelated failures, so I'll ship this!

libunwind/src/CMakeLists.txt

 # Get sources
 
 set(LIBUNWIND_CXX_SOURCES
     libunwind.cpp
     Unwind-EHABI.cpp
     Unwind-seh.cpp
     )
-if(APPLE)
-  list(APPEND LIBUNWIND_CXX_SOURCES
-    Unwind_AppleExtras.cpp
-    )
-endif()
 
 if(${CMAKE_SYSTEM_NAME} MATCHES "AIX")
   list(APPEND LIBUNWIND_CXX_SOURCES
     Unwind_AIXExtras.cpp
     )
 endif()
 
 set(LIBUNWIND_C_SOURCES

libunwind/src/Unwind_AppleExtras.cpp

-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//
-//===----------------------------------------------------------------------===//
-
-#include "config.h"
-
-#include <TargetConditionals.h>
-
-
-// static linker symbols to prevent wrong two level namespace for _Unwind symbols
-#if defined(__arm__)
-#  if defined(__USING_SJLJ_EXCEPTIONS__) && TARGET_OS_IOS
-#     define NOT_HERE_BEFORE_5_0(sym)     \
-       extern const char sym##_tmp30 __asm("$ld$hide$os3.0$_" #sym ); \
-       __attribute__((visibility("default"))) const char sym##_tmp30 = 0; \
-       extern const char sym##_tmp31 __asm("$ld$hide$os3.1$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp31 = 0; \
-       extern const char sym##_tmp32 __asm("$ld$hide$os3.2$_" #sym );\
-           __attribute__((visibility("default"))) const char sym##_tmp32 = 0; \
-       extern const char sym##_tmp40 __asm("$ld$hide$os4.0$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp40 = 0; \
-       extern const char sym##_tmp41 __asm("$ld$hide$os4.1$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp41 = 0; \
-       extern const char sym##_tmp42 __asm("$ld$hide$os4.2$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp42 = 0; \
-       extern const char sym##_tmp43 __asm("$ld$hide$os4.3$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp43 = 0;
-#  else // defined(__USING_SJLJ_EXCEPTIONS__) && TARGET_OS_IOS
-#     define NOT_HERE_BEFORE_5_0(sym)
-#     define NOT_HERE_BEFORE_10_6(sym)
-#     define NEVER_HERE(sym)
-#  endif // defined(__USING_SJLJ_EXCEPTIONS__) && TARGET_OS_IOS
-#elif TARGET_OS_OSX && !defined(__aarch64__)
-#  define NOT_HERE_BEFORE_10_6(sym) \
-    extern const char sym##_tmp4 __asm("$ld$hide$os10.4$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp4 = 0; \
-    extern const char sym##_tmp5 __asm("$ld$hide$os10.5$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp5 = 0;
-#  define NEVER_HERE(sym) \
-    extern const char sym##_tmp4 __asm("$ld$hide$os10.4$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp4 = 0; \
-    extern const char sym##_tmp5 __asm("$ld$hide$os10.5$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp5 = 0; \
-    extern const char sym##_tmp6 __asm("$ld$hide$os10.6$_" #sym ); \
-          __attribute__((visibility("default"))) const char sym##_tmp6 = 0;
-#else
-#  define NOT_HERE_BEFORE_10_6(sym)
-#  define NEVER_HERE(sym)
-#endif
-
-
-#if defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)
-
-//
-// symbols in libSystem.dylib in 10.6 and later, but are in libgcc_s.dylib in
-// earlier versions
-//
-NOT_HERE_BEFORE_10_6(_Unwind_DeleteException)
-NOT_HERE_BEFORE_10_6(_Unwind_Find_FDE)
-NOT_HERE_BEFORE_10_6(_Unwind_ForcedUnwind)
-NOT_HERE_BEFORE_10_6(_Unwind_GetGR)
-NOT_HERE_BEFORE_10_6(_Unwind_GetIP)
-NOT_HERE_BEFORE_10_6(_Unwind_GetLanguageSpecificData)
-NOT_HERE_BEFORE_10_6(_Unwind_GetRegionStart)
-NOT_HERE_BEFORE_10_6(_Unwind_RaiseException)
-NOT_HERE_BEFORE_10_6(_Unwind_Resume)
-NOT_HERE_BEFORE_10_6(_Unwind_SetGR)
-NOT_HERE_BEFORE_10_6(_Unwind_SetIP)
-NOT_HERE_BEFORE_10_6(_Unwind_Backtrace)
-NOT_HERE_BEFORE_10_6(_Unwind_FindEnclosingFunction)
-NOT_HERE_BEFORE_10_6(_Unwind_GetCFA)
-NOT_HERE_BEFORE_10_6(_Unwind_GetDataRelBase)
-NOT_HERE_BEFORE_10_6(_Unwind_GetTextRelBase)
-NOT_HERE_BEFORE_10_6(_Unwind_Resume_or_Rethrow)
-NOT_HERE_BEFORE_10_6(_Unwind_GetIPInfo)
-NOT_HERE_BEFORE_10_6(__register_frame)
-NOT_HERE_BEFORE_10_6(__deregister_frame)
-
-//
-// symbols in libSystem.dylib for compatibility, but we don't want any new code
-// using them
-//
-NEVER_HERE(__register_frame_info_bases)
-NEVER_HERE(__register_frame_info)
-NEVER_HERE(__register_frame_info_table_bases)
-NEVER_HERE(__register_frame_info_table)
-NEVER_HERE(__register_frame_table)
-NEVER_HERE(__deregister_frame_info)
-NEVER_HERE(__deregister_frame_info_bases)
-
-#endif // defined(_LIBUNWIND_BUILD_ZERO_COST_APIS)
-
-
-
-
-#if defined(_LIBUNWIND_BUILD_SJLJ_APIS)
-//
-// symbols in libSystem.dylib in iOS 5.0 and later, but are in libgcc_s.dylib in
-// earlier versions
-//
-NOT_HERE_BEFORE_5_0(_Unwind_GetLanguageSpecificData)
-NOT_HERE_BEFORE_5_0(_Unwind_GetRegionStart)
-NOT_HERE_BEFORE_5_0(_Unwind_GetIP)
-NOT_HERE_BEFORE_5_0(_Unwind_SetGR)
-NOT_HERE_BEFORE_5_0(_Unwind_SetIP)
-NOT_HERE_BEFORE_5_0(_Unwind_DeleteException)
-NOT_HERE_BEFORE_5_0(_Unwind_SjLj_Register)
-NOT_HERE_BEFORE_5_0(_Unwind_GetGR)
-NOT_HERE_BEFORE_5_0(_Unwind_GetIPInfo)
-NOT_HERE_BEFORE_5_0(_Unwind_GetCFA)
-NOT_HERE_BEFORE_5_0(_Unwind_SjLj_Resume)
-NOT_HERE_BEFORE_5_0(_Unwind_SjLj_RaiseException)
-NOT_HERE_BEFORE_5_0(_Unwind_SjLj_Resume_or_Rethrow)
-NOT_HERE_BEFORE_5_0(_Unwind_SjLj_Unregister)
-
-#endif // defined(_LIBUNWIND_BUILD_SJLJ_APIS)