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[libcxxabi] Fix cmake order dependency wrt dllexporting 

If LIBCXX_ENABLE_SHARED isn't explicitly set on the cmake command
line, isn't set in the cache, and the libcxxabi project is configured
before libcxx, then LIBCXX_ENABLE_SHARED isn't defined yet. Once
the libcxx cmake project has been parsed, LIBCXX_ENABLE_SHARED would
have been set to its default value of ON.

This makes sure that the symbols are properly dllexported in such
a configuration scenario.

Differential Revision: https://reviews.llvm.org/D120982
This commit is contained in:
Martin Storsjö 2022-03-07 13:32:52 -05:00 committed by Louis Dionne
parent bed3240bf7
commit ebde6fc23b
2 changed files with 13 additions and 1 deletions
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5
libcxx/docs/ReleaseNotes.rst
View File

@ -93,3 +93,8 @@ Build System Changes
``{LIBCXX,LIBCXXABI,LIBUNWIND}_GCC_TOOLCHAIN`` CMake variables have been removed. Instead, please
use the ``CMAKE_CXX_COMPILER_TARGET``, ``CMAKE_SYSROOT`` and ``CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN``
variables provided by CMake.
- When building for Windows, vendors who want to avoid dll-exporting symbols from the static libc++abi
library should set ``LIBCXXABI_HERMETIC_STATIC_LIBRARY=ON`` when configuring CMake. The current
behavior, which tries to guess the correct dll-export semantics based on whether we're building
the libc++ shared library, will be removed in LLVM 16.

9
libcxxabi/CMakeLists.txt
View File

@ -302,13 +302,20 @@ add_definitions(-D_LIBCPP_BUILDING_LIBRARY)
# Disable DLL annotations on Windows for static builds.
if (WIN32 AND LIBCXXABI_ENABLE_STATIC AND NOT LIBCXXABI_ENABLE_SHARED)
if (LIBCXX_ENABLE_SHARED AND LIBCXX_ENABLE_STATIC_ABI_LIBRARY)
# If LIBCXX_ENABLE_SHARED isn't set (by the user on the cmake command
# line or via a cache file), use its expected default value (enabled).
if ((LIBCXX_ENABLE_SHARED OR NOT DEFINED LIBCXX_ENABLE_SHARED) AND LIBCXX_ENABLE_STATIC_ABI_LIBRARY)
# Building libcxxabi statically, but intending for it to be statically
# linked into a shared libcxx; keep dllexport enabled within libcxxabi,
# as the symbols will need to be exported from libcxx.
else()
# Regular static build; disable dllexports.
add_definitions(-D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS)
if (NOT LIBCXXABI_HERMETIC_STATIC_LIBRARY)
# TODO: Enable this warning message as soon as we're sure this is the solution.
# message(WARNING "Implicitly disabling dllexport on Win32 is not supported anymore. Please build with "
# "LIBCXXABI_HERMETIC_STATIC_LIBRARY=ON instead. This will become an error in LLVM 16.")
endif()
endif()
endif()