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release/19.x: [libc++] Avoid re-exporting a few specific symbols from libc++abi (#109054) #110677

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release/19.x: [libc++] Avoid re-exporting a few specific symbols from libc++abi (#109054) #110677

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30 changes: 30 additions & 0 deletions libcxx/lib/abi/CHANGELOG.TXT
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Expand Up @@ -16,6 +16,36 @@ New entries should be added directly below the "Version" header.
Version 19.0
------------

* [libc++] Avoid re-exporting a few specific symbols from libc++abi

In 6a884a9aef39, I synchronized the export list of libc++abi to the
export list of libc++. From the linker's perspective, this caused
these symbols to be taken from libc++.dylib instead of libc++abi.dylib.

However, that can be problematic when back-deploying. Indeed, this means
that the linker will encode an undefined reference to be fullfilled by
libc++.dylib, but when backdeploying against an older system, that symbol
might only be available in libc++abi.dylib.

Most of the symbols that started being re-exported after 6a884a9aef39
turn out to be implementation details of libc++abi, so nobody really
depends on them and this back-deployment issue is inconsequential.

However, we ran into issues with a few of these symbols while testing
LLVM 19, which led to this patch.

In the future, a follow-up cleanup would be to stop exporting most of
the _cxxabiv1_foo_type_infoE symbols from both libc++abi and libc++
since they are implementation details that nobody should be relying
on.

<arch>-apple-darwin
-------------------
Symbol not reexported anymore: ___cxa_rethrow_primary_exception
Symbol not reexported anymore: __ZTIN10__cxxabiv117__class_type_infoE
Symbol not reexported anymore: __ZTIN10__cxxabiv120__si_class_type_infoE
Symbol not reexported anymore: __ZTIN10__cxxabiv121__vmi_class_type_infoE

* [libc++] Always keep libc++abi re-exports up-to-date

This patch makes sure that the set of libc++abi symbols re-exported from libc++
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7 changes: 0 additions & 7 deletions libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
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Expand Up @@ -78,12 +78,9 @@
{'is_defined': False, 'name': '__ZTIN10__cxxabiv116__enum_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv116__shim_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv117__array_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv117__class_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv117__pbase_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv119__pointer_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv120__function_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv120__si_class_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv121__vmi_class_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv123__fundamental_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv129__pointer_to_member_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIPDh', 'type': 'U'}
Expand Down Expand Up @@ -2002,12 +1999,9 @@
{'is_defined': True, 'name': '__ZTIN10__cxxabiv116__enum_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv116__shim_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv117__array_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv117__class_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv117__pbase_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv119__pointer_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv120__function_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv120__si_class_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv121__vmi_class_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv123__fundamental_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv129__pointer_to_member_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTINSt12experimental15fundamentals_v112bad_any_castE', 'size': 0, 'type': 'OBJECT'}
Expand Down Expand Up @@ -2615,7 +2609,6 @@
{'is_defined': True, 'name': '___cxa_new_handler', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_pure_virtual', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_rethrow', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_rethrow_primary_exception', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_terminate_handler', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_throw', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_throw_bad_array_new_length', 'type': 'I'}
Expand Down
7 changes: 0 additions & 7 deletions libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.nonew.abilist
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Expand Up @@ -78,12 +78,9 @@
{'is_defined': False, 'name': '__ZTIN10__cxxabiv116__enum_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv116__shim_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv117__array_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv117__class_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv117__pbase_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv119__pointer_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv120__function_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv120__si_class_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv121__vmi_class_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv123__fundamental_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIN10__cxxabiv129__pointer_to_member_type_infoE', 'type': 'U'}
{'is_defined': False, 'name': '__ZTIPDh', 'type': 'U'}
Expand Down Expand Up @@ -2002,12 +1999,9 @@
{'is_defined': True, 'name': '__ZTIN10__cxxabiv116__enum_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv116__shim_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv117__array_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv117__class_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv117__pbase_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv119__pointer_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv120__function_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv120__si_class_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv121__vmi_class_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv123__fundamental_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTIN10__cxxabiv129__pointer_to_member_type_infoE', 'type': 'I'}
{'is_defined': True, 'name': '__ZTINSt12experimental15fundamentals_v112bad_any_castE', 'size': 0, 'type': 'OBJECT'}
Expand Down Expand Up @@ -2649,7 +2643,6 @@
{'is_defined': True, 'name': '___cxa_new_handler', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_pure_virtual', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_rethrow', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_rethrow_primary_exception', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_terminate_handler', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_throw', 'type': 'I'}
{'is_defined': True, 'name': '___cxa_throw_bad_array_new_length', 'type': 'I'}
Expand Down
3 changes: 0 additions & 3 deletions libcxxabi/lib/cxxabiv1.exp
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Expand Up @@ -2,12 +2,9 @@
__ZTIN10__cxxabiv116__enum_type_infoE
__ZTIN10__cxxabiv116__shim_type_infoE
__ZTIN10__cxxabiv117__array_type_infoE
__ZTIN10__cxxabiv117__class_type_infoE
__ZTIN10__cxxabiv117__pbase_type_infoE
__ZTIN10__cxxabiv119__pointer_type_infoE
__ZTIN10__cxxabiv120__function_type_infoE
__ZTIN10__cxxabiv120__si_class_type_infoE
__ZTIN10__cxxabiv121__vmi_class_type_infoE
__ZTIN10__cxxabiv123__fundamental_type_infoE
__ZTIN10__cxxabiv129__pointer_to_member_type_infoE

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1 change: 0 additions & 1 deletion libcxxabi/lib/itanium-base.exp
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Expand Up @@ -12,7 +12,6 @@ ___cxa_guard_acquire
___cxa_guard_release
___cxa_increment_exception_refcount
___cxa_pure_virtual
___cxa_rethrow_primary_exception
___cxa_throw_bad_array_new_length
___cxa_uncaught_exception
___cxa_uncaught_exceptions
Expand Down
13 changes: 13 additions & 0 deletions libcxxabi/lib/symbols-not-reexported.exp
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@@ -0,0 +1,13 @@
# These symbols are not re-exported from libc++ because providing a definition in libc++ causes
# issues with some clients when backdeploying.

# These symbols are implementation details of libc++abi, but they are referenced from UBSan
# (which is a total hack). We'll need to figure out how to decouple UBSan from these details
# before we can stop exporting them from libc++abi.
__ZTIN10__cxxabiv117__class_type_infoE
__ZTIN10__cxxabiv120__si_class_type_infoE
__ZTIN10__cxxabiv121__vmi_class_type_infoE

# This symbol is not an implementation detail of libc++abi, but it also causes issues when moving
# to libc++. This needs further investigation.
___cxa_rethrow_primary_exception
10 changes: 9 additions & 1 deletion libcxxabi/src/CMakeLists.txt
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Expand Up @@ -214,14 +214,22 @@ if (LIBCXXABI_ENABLE_SHARED)
endif()

add_library(cxxabi-reexports INTERFACE)
function(reexport_symbols file)
function(export_symbols file)
# -exported_symbols_list is only available on Apple platforms
if (APPLE)
target_link_libraries(cxxabi_shared PRIVATE "-Wl,-exported_symbols_list,${file}")
endif()
endfunction()

function(reexport_symbols file)
export_symbols("${file}")
# -reexported_symbols_list is only available on Apple platforms
if (APPLE)
target_link_libraries(cxxabi-reexports INTERFACE "-Wl,-reexported_symbols_list,${file}")
endif()
endfunction()

export_symbols("${CMAKE_CURRENT_SOURCE_DIR}/../lib/symbols-not-reexported.exp")
reexport_symbols("${CMAKE_CURRENT_SOURCE_DIR}/../lib/cxxabiv1.exp")
reexport_symbols("${CMAKE_CURRENT_SOURCE_DIR}/../lib/fundamental-types.exp")
reexport_symbols("${CMAKE_CURRENT_SOURCE_DIR}/../lib/itanium-base.exp")
Expand Down
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