Do not require libatomic on FreeBSD

f3e09f36 hooked a dependency on libatomic on 32 bit machines if Clang is
used because compilation failed with:

`std::__atomic_base<unsigned long long>::load(std::memory_order) const':
/usr/bin/../lib/gcc/i686-pc-linux-gnu/6.1.1/../../../../include/c++/6.1.1/bits/atomic_base.h:396:
undefined reference to `__atomic_load_8'

But that does not happen on FreeBSD. The problem is likely that on Linux
Clang tries to use GCC-provided C++11 library. Further,
__atomic_load_8() (for 8-byte integers) is not readily available on 32
bit machines. From https://gcc.gnu.org/wiki/Atomic/GCCMM: "When lock
free instructions are not available (either through hardware or OS
support) atomic operations are left as function calls to be resolved by
a library."
This commit is contained in:
Vasil Dimov 2017-11-11 15:29:42 +02:00
parent af448d3883
commit 3501ed1fdf
No known key found for this signature in database
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1 changed files with 1 additions and 1 deletions

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@ -698,7 +698,7 @@ endif()
if(ANDROID)
set(ATOMIC libatomic.a)
endif()
if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND ARCH_WIDTH EQUAL "32" AND NOT IOS)
if(CMAKE_C_COMPILER_ID STREQUAL "Clang" AND ARCH_WIDTH EQUAL "32" AND NOT IOS AND NOT FREEBSD)
find_library(ATOMIC atomic)
list(APPEND EXTRA_LIBRARIES ${ATOMIC})
endif()