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[libc++] Define new/delete in libc++abi only by default 

Previously, we would define new/delete in both libc++ and libc++abi.
Not only does this cause code bloat, but also it's technically an ODR
violation since we don't know which operator will be selected. Furthermore,
since those are weak definitions, we should strive to have as few of them
as possible (to improve load times).

My preferred choice would have been to put the operators in libc++ only
by default, however that would create a circular dependency between
libc++ and libc++abi, which GNU linkers don't handle.

Folks who want to ship new/delete in libc++ instead of libc++abi are
free to do so by turning on LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS at
CMake configure time.

On Apple platforms, this shouldn't be an ABI break because we re-export
the new/delete symbols from libc++abi. This change actually makes libc++
behave closer to the system libc++ shipped on Apple platforms.

On other platforms, this is an ABI break for people linking against libc++
but not libc++abi. However, vendors have been consulted in D68269 and no
objection was raised. Furthermore, the definitions can be controlled to
appear in libc++ instead with the CMake option.

Differential Revision: https://reviews.llvm.org/D68269
This commit is contained in:
Louis Dionne 2019-10-01 09:34:58 -04:00
parent b20918997a
commit 9b40ee8eb0
10 changed files with 121 additions and 61 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
libcxx/CMakeLists.txt
View File

@ -232,10 +232,10 @@ option(LIBCXX_ENABLE_ABI_LINKER_SCRIPT
${ENABLE_LINKER_SCRIPT_DEFAULT_VALUE})
option(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS
"Build libc++ with definitions for operator new/delete. This option can
be used to disable the definitions when libc++abi is expected to provide
them" ON)
"Build libc++ with definitions for operator new/delete. These are normally
defined in libc++abi, but this option can be used to define them in libc++
instead. If you define them in libc++, make sure they are NOT defined in
libc++abi. Doing otherwise is an ODR violation." OFF)
# Build libc++abi with libunwind. We need this option to determine whether to
# link with libunwind or libgcc_s while running the test cases.
option(LIBCXXABI_USE_LLVM_UNWINDER "Build and use the LLVM unwinder." OFF)

2
libcxx/cmake/caches/Apple.cmake
View File

@ -9,11 +9,9 @@ set(LIBCXX_ENABLE_STATIC OFF CACHE BOOL "")
set(LIBCXX_ENABLE_SHARED ON CACHE BOOL "")
set(LIBCXX_TYPEINFO_COMPARISON_IMPLEMENTATION "1" CACHE STRING "")
set(LIBCXX_CXX_ABI libcxxabi CACHE STRING "")
set(LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS OFF CACHE BOOL "")
set(LIBCXX_HIDE_FROM_ABI_PER_TU_BY_DEFAULT ON CACHE BOOL "")
set(LIBCXX_ENABLE_DEBUG_MODE_SUPPORT OFF CACHE BOOL "")
set(LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS ON CACHE BOOL "")
set(LIBCXXABI_ENABLE_PIC OFF CACHE BOOL "")
set(LIBCXXABI_ENABLE_ASSERTIONS OFF CACHE BOOL "")
set(LIBCXXABI_ENABLE_FORGIVING_DYNAMIC_CAST ON CACHE BOOL "")

8
libcxx/docs/ReleaseNotes.rst
View File

@ -42,4 +42,10 @@ New Features
API Changes
-----------
- ...
- By default, libc++ will _not_ include the definition for new and delete,
since those are provided in libc++abi. Vendors wishing to provide new and
delete in libc++ can build the library with ``-DLIBCXX_ENABLE_NEW_DELETE_DEFINITIONS=ON``
to get back the old behavior. This was done to avoid providing new and delete
in both libc++ and libc++abi, which is technically an ODR violation. Also
note that we couldn't decide to put the operators in libc++ only, because
they are needed from libc++abi (which would create a circular dependency).

59
libcxx/lib/abi/CHANGELOG.TXT
View File

@ -16,6 +16,65 @@ New entries should be added directly below the "Version" header.
Version 12.0
------------
* XXXXXXX - [libc++] Define new/delete in libc++abi only by default
By default, libc++ does not include the definition for new and delete anymore.
Those were previously defined in both libc++ and libc++abi, which was an
ODR violation.
x86_64-apple-apple-darwin
-------------------------
The following symbols are now re-exported from libc++abi instead of exported
by libc++ directly (this should not be an ABI break):
Symbol moved: __ZdaPv
Symbol moved: __ZdaPvm
Symbol moved: __ZdaPvmSt11align_val_t
Symbol moved: __ZdaPvRKSt9nothrow_t
Symbol moved: __ZdaPvSt11align_val_t
Symbol moved: __ZdaPvSt11align_val_tRKSt9nothrow_t
Symbol moved: __ZdlPv
Symbol moved: __ZdlPvm
Symbol moved: __ZdlPvmSt11align_val_t
Symbol moved: __ZdlPvRKSt9nothrow_t
Symbol moved: __ZdlPvSt11align_val_t
Symbol moved: __ZdlPvSt11align_val_tRKSt9nothrow_t
Symbol moved: __Znam
Symbol moved: __ZnamRKSt9nothrow_t
Symbol moved: __ZnamSt11align_val_t
Symbol moved: __ZnamSt11align_val_tRKSt9nothrow_t
Symbol moved: __Znwm
Symbol moved: __ZnwmRKSt9nothrow_t
Symbol moved: __ZnwmSt11align_val_t
Symbol moved: __ZnwmSt11align_val_tRKSt9nothrow_t
x86_64-unknown-linux-gnu
------------------------
The following symbols were moved to libc++abi, but are NOT being re-exported
by libc++. This constitutes an ABI break if one links against libc++ but
not libc++abi.
Symbol moved: _ZdaPv
Symbol moved: _ZdaPvm
Symbol moved: _ZdaPvmSt11align_val_t
Symbol moved: _ZdaPvRKSt9nothrow_t
Symbol moved: _ZdaPvSt11align_val_t
Symbol moved: _ZdaPvSt11align_val_tRKSt9nothrow_t
Symbol moved: _ZdlPv
Symbol moved: _ZdlPvm
Symbol moved: _ZdlPvmSt11align_val_t
Symbol moved: _ZdlPvRKSt9nothrow_t
Symbol moved: _ZdlPvSt11align_val_t
Symbol moved: _ZdlPvSt11align_val_tRKSt9nothrow_t
Symbol moved: _Znam
Symbol moved: _ZnamRKSt9nothrow_t
Symbol moved: _ZnamSt11align_val_t
Symbol moved: _ZnamSt11align_val_tRKSt9nothrow_t
Symbol moved: _Znwm
Symbol moved: _ZnwmRKSt9nothrow_t
Symbol moved: _ZnwmSt11align_val_t
Symbol moved: _ZnwmSt11align_val_tRKSt9nothrow_t
* 4f13b9992971 - [libc++] Simplify how we re-export symbols from libc++abi
We re-export some symbols that were exported from libc++abi but not from

2
libcxx/lib/abi/CMakeLists.txt
View File

@ -23,7 +23,7 @@ if (EXISTS "${ABILIST_FILE}"
(APPLE AND "${LIBCXX_CXX_ABI_LIBNAME}" STREQUAL "default"))
AND NOT LIBCXX_ABI_UNSTABLE
AND LIBCXX_ENABLE_EXCEPTIONS
AND LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
AND NOT LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
add_custom_target(check-cxx-abilist
${SYMDIFF_EXE} --only-stdlib-symbols --strict ${ABILIST_FILE}
$<TARGET_SONAME_FILE:cxx_shared>

60
libcxx/lib/abi/x86_64-apple-darwin.v1.abilist
View File

@ -2258,26 +2258,46 @@
{'is_defined': True, 'name': '__ZTv0_n24_NSt3__114basic_iostreamIcNS_11char_traitsIcEEED1Ev', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZTv0_n24_NSt3__19strstreamD0Ev', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZTv0_n24_NSt3__19strstreamD1Ev', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdaPv', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdaPvRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdaPvSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdaPvSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdaPvm', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdaPvmSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdlPv', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdlPvRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdlPvSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdlPvSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdlPvm', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZdlPvmSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__Znam', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZnamRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZnamSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZnamSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__Znwm', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZnwmRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZnwmSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '__ZnwmSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': False, 'name': '__ZdaPv', 'type': 'U'}
{'is_defined': True, 'name': '__ZdaPv', 'type': 'I'}
{'is_defined': False, 'name': '__ZdaPvRKSt9nothrow_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZdaPvRKSt9nothrow_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZdaPvSt11align_val_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZdaPvSt11align_val_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZdaPvSt11align_val_tRKSt9nothrow_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZdaPvSt11align_val_tRKSt9nothrow_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZdaPvm', 'type': 'U'}
{'is_defined': True, 'name': '__ZdaPvm', 'type': 'I'}
{'is_defined': False, 'name': '__ZdaPvmSt11align_val_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZdaPvmSt11align_val_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZdlPv', 'type': 'U'}
{'is_defined': True, 'name': '__ZdlPv', 'type': 'I'}
{'is_defined': False, 'name': '__ZdlPvRKSt9nothrow_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZdlPvRKSt9nothrow_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZdlPvSt11align_val_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZdlPvSt11align_val_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZdlPvSt11align_val_tRKSt9nothrow_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZdlPvSt11align_val_tRKSt9nothrow_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZdlPvm', 'type': 'U'}
{'is_defined': True, 'name': '__ZdlPvm', 'type': 'I'}
{'is_defined': False, 'name': '__ZdlPvmSt11align_val_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZdlPvmSt11align_val_t', 'type': 'I'}
{'is_defined': False, 'name': '__Znam', 'type': 'U'}
{'is_defined': True, 'name': '__Znam', 'type': 'I'}
{'is_defined': False, 'name': '__ZnamRKSt9nothrow_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZnamRKSt9nothrow_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZnamSt11align_val_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZnamSt11align_val_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZnamSt11align_val_tRKSt9nothrow_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZnamSt11align_val_tRKSt9nothrow_t', 'type': 'I'}
{'is_defined': False, 'name': '__Znwm', 'type': 'U'}
{'is_defined': True, 'name': '__Znwm', 'type': 'I'}
{'is_defined': False, 'name': '__ZnwmRKSt9nothrow_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZnwmRKSt9nothrow_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZnwmSt11align_val_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZnwmSt11align_val_t', 'type': 'I'}
{'is_defined': False, 'name': '__ZnwmSt11align_val_tRKSt9nothrow_t', 'type': 'U'}
{'is_defined': True, 'name': '__ZnwmSt11align_val_tRKSt9nothrow_t', 'type': 'I'}
{'is_defined': False, 'name': '___cxa_allocate_exception', 'type': 'U'}
{'is_defined': True, 'name': '___cxa_allocate_exception', 'type': 'I'}
{'is_defined': False, 'name': '___cxa_atexit', 'type': 'U'}

27
libcxx/lib/abi/x86_64-unknown-linux-gnu.v1.abilist
View File

@ -1491,7 +1491,6 @@
{'is_defined': False, 'name': '_ZNSt9bad_allocC1Ev', 'type': 'FUNC'}
{'is_defined': False, 'name': '_ZNSt9bad_allocD1Ev', 'type': 'FUNC'}
{'is_defined': False, 'name': '_ZNSt9exceptionD2Ev', 'type': 'FUNC'}
{'is_defined': False, 'name': '_ZSt15get_new_handlerv', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZSt17__throw_bad_allocv', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZSt17current_exceptionv', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZSt17rethrow_exceptionSt13exception_ptr', 'type': 'FUNC'}
@ -1882,26 +1881,12 @@
{'is_defined': True, 'name': '_ZTv0_n24_NSt3__114basic_iostreamIcNS_11char_traitsIcEEED1Ev', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZTv0_n24_NSt3__19strstreamD0Ev', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZTv0_n24_NSt3__19strstreamD1Ev', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdaPv', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdaPvRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdaPvSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdaPvSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdaPvm', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdaPvmSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdlPv', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdlPvRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdlPvSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdlPvSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdlPvm', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZdlPvmSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_Znam', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZnamRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZnamSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZnamSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_Znwm', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZnwmRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZnwmSt11align_val_t', 'type': 'FUNC'}
{'is_defined': True, 'name': '_ZnwmSt11align_val_tRKSt9nothrow_t', 'type': 'FUNC'}
{'is_defined': False, 'name': '_ZdaPv', 'type': 'FUNC'}
{'is_defined': False, 'name': '_ZdaPvSt11align_val_t', 'type': 'FUNC'}
{'is_defined': False, 'name': '_ZdlPv', 'type': 'FUNC'}
{'is_defined': False, 'name': '_Znam', 'type': 'FUNC'}
{'is_defined': False, 'name': '_ZnamSt11align_val_t', 'type': 'FUNC'}
{'is_defined': False, 'name': '_Znwm', 'type': 'FUNC'}
{'is_defined': False, 'name': '__cxa_allocate_exception', 'type': 'FUNC'}
{'is_defined': False, 'name': '__cxa_begin_catch', 'type': 'FUNC'}
{'is_defined': False, 'name': '__cxa_current_primary_exception', 'type': 'FUNC'}

5
libcxx/src/CMakeLists.txt
View File

@ -222,11 +222,6 @@ if (LIBCXX_ENABLE_SHARED)
"-Wl,-reexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/../lib/libc++abi.v${LIBCXX_LIBCPPABI_VERSION}.exp"
"-Wl,-force_symbols_not_weak_list,${CMAKE_CURRENT_SOURCE_DIR}/../lib/notweak.exp"
"-Wl,-force_symbols_weak_list,${CMAKE_CURRENT_SOURCE_DIR}/../lib/weak.exp")
if (NOT LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
target_link_libraries(cxx_shared PRIVATE
"-Wl,-reexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/../../libcxxabi/lib/new-delete.exp")
endif()
endif()
# Generate a linker script in place of a libc++.so symlink.

9
libcxxabi/CMakeLists.txt
View File

@ -87,13 +87,10 @@ When the dynamic_cast would normally fail, this option will cause the \
library to try comparing the type_info names to see if they are equal \
instead." OFF)
# FIXME: This option should default to off. Unfortunatly GCC 4.9 fails to link
# programs to due undefined references to new/delete in libc++abi. Once this
# has been fixed or worked around the default value should be changed.
# See https://reviews.llvm.org/D68269 for more details.
option(LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS
"Build libc++abi with definitions for operator new/delete. Normally libc++
provides these definitions" ON)
"Build libc++abi with definitions for operator new/delete. These are normally
defined in libc++abi, but it is also possible to define them in libc++, in
which case the definition in libc++abi should be turned off." ON)
option(LIBCXXABI_BUILD_32_BITS "Build 32 bit libc++abi." ${LLVM_BUILD_32_BITS})
option(LIBCXXABI_INCLUDE_TESTS "Generate build targets for the libc++abi unit tests." ${LLVM_INCLUDE_TESTS})
set(LIBCXXABI_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING

2
libcxxabi/src/CMakeLists.txt
View File

@ -215,7 +215,7 @@ if (LIBCXXABI_ENABLE_SHARED)
export_symbols("${CMAKE_CURRENT_SOURCE_DIR}/../lib/itanium-base.exp")
if (LIBCXXABI_ENABLE_NEW_DELETE_DEFINITIONS)
export_symbols("${CMAKE_CURRENT_SOURCE_DIR}/../lib/new-delete.exp")
reexport_symbols("${CMAKE_CURRENT_SOURCE_DIR}/../lib/new-delete.exp")
endif()
if (LIBCXXABI_ENABLE_EXCEPTIONS)