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Merge #4571

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4571: Add CheckAtomic.cmake r=def- a=yangfl

Sometimes linking against libatomic is required for atomic ops, if
the platform doesn't support lock-free atomics.

This is a fixup for #4556, which does not work as intended.

<!-- What is the motivation for the changes of this pull request -->

## Checklist

- [ ] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test if it works standalone, system.c especially
- [ ] Considered possible null pointers and out of bounds array indexing
- [ ] Changed no physics that affect existing maps
- [ ] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: yangfl <yangfl@users.noreply.github.com>
This commit is contained in:
bors[bot] 2022-01-07 16:41:55 +00:00 committed by GitHub
parent f3f6db1794 b072c44c08
commit cd992e8fdc
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2 changed files with 53 additions and 0 deletions
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1
CMakeLists.txt
View file

@ -83,6 +83,7 @@ endif()
include(CheckCCompilerFlag)
include(CheckCXXCompilerFlag)
include(CheckSymbolExists)
include(CheckAtomic)
check_symbol_exists(__i386 "" TARGET_ARCH_X86_i386)
if(TARGET_ARCH_X86_i386)

52
cmake/CheckAtomic.cmake Normal file
View file

@ -0,0 +1,52 @@
include(CheckCXXSourceCompiles)
include(CheckLibraryExists)
# Sometimes linking against libatomic is required for atomic ops, if
# the platform doesn't support lock-free atomics.
function(check_working_cxx_atomics varname)
set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++11")
check_cxx_source_compiles("
#include <atomic>
#include <cstdint>
std::atomic<uint64_t> x (0);
int main() {
uint64_t i = x.load(std::memory_order_relaxed);
(void)i;
return 0;
}
" ${varname})
set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
endfunction(check_working_cxx_atomics)
if(NOT DEFINED COMPILER_IS_GCC_COMPATIBLE)
if(MSVC OR APPLE)
set(COMPILER_IS_GCC_COMPATIBLE OFF)
else()
set(COMPILER_IS_GCC_COMPATIBLE ON)
endif()
endif()
if(NOT COMPILER_IS_GCC_COMPATIBLE)
set(HAVE_ATOMICS_WITHOUT_LIB ON)
else()
# Check for 64 bit atomic operations.
# First check if atomics work without the library.
check_working_cxx_atomics(HAVE_ATOMICS_WITHOUT_LIB)
# If not, check if the library exists, and atomics work with it.
if(NOT HAVE_ATOMICS_WITHOUT_LIB)
check_library_exists(atomic __atomic_load_8 "" HAVE_LIBATOMICS)
mark_as_advanced(HAVE_LIBATOMICS)
if(NOT HAVE_LIBATOMICS)
message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
endif()
list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
check_working_cxx_atomics(HAVE_ATOMICS_WITH_LIB)
if(NOT HAVE_ATOMICS_WITH_LIB)
message(FATAL_ERROR "Host compiler must support std::atomic!")
endif()
list(APPEND CMAKE_C_STANDARD_LIBRARIES "-latomic")
list(APPEND CMAKE_CXX_STANDARD_LIBRARIES "-latomic")
endif()
endif()