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#
# SRT - Secure, Reliable, Transport Copyright (c) 2021 Haivision Systems Inc.
#
# This Source Code Form is subject to the terms of the Mozilla Public License,
# v. 2.0. If a copy of the MPL was not distributed with this file, You can
# obtain one at http://mozilla.org/MPL/2.0/.
#
# Check for GCC Atomic Intrinsics and whether libatomic is required.
#
# Sets:
# HAVE_LIBATOMIC
# HAVE_LIBATOMIC_COMPILES
# HAVE_LIBATOMIC_COMPILES_STATIC
# HAVE_GCCATOMIC_INTRINSICS
# HAVE_GCCATOMIC_INTRINSICS_REQUIRES_LIBATOMIC
#
# See
# https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html
# https://gcc.gnu.org/wiki/Atomic/GCCMM/AtomicSync
include(CheckCSourceCompiles)
include(CheckLibraryExists)
function(CheckGCCAtomicIntrinsics)
unset(HAVE_LIBATOMIC CACHE)
unset(HAVE_LIBATOMIC_COMPILES CACHE)
unset(HAVE_LIBATOMIC_COMPILES_STATIC CACHE)
unset(HAVE_GCCATOMIC_INTRINSICS CACHE)
unset(HAVE_GCCATOMIC_INTRINSICS_REQUIRES_LIBATOMIC CACHE)
set(CMAKE_TRY_COMPILE_TARGET_TYPE EXECUTABLE) # CMake 3.6
unset(CMAKE_REQUIRED_FLAGS)
unset(CMAKE_REQUIRED_LIBRARIES)
unset(CMAKE_REQUIRED_LINK_OPTIONS)
# Check for existence of libatomic and whether this symbol is present.
check_library_exists(atomic __atomic_fetch_add_8 "" HAVE_LIBATOMIC)
set(CheckLibAtomicCompiles_CODE
"
int main(void)
{
const int result = 0;
return result;
}
")
set(CMAKE_REQUIRED_LIBRARIES "atomic")
# Check that the compiler can build a simple application and link with
# libatomic.
check_c_source_compiles("${CheckLibAtomicCompiles_CODE}"
HAVE_LIBATOMIC_COMPILES)
if(NOT HAVE_LIBATOMIC_COMPILES)
set(HAVE_LIBATOMIC
0
CACHE INTERNAL "" FORCE)
endif()
if(HAVE_LIBATOMIC AND HAVE_LIBATOMIC_COMPILES)
# CMAKE_REQUIRED_LINK_OPTIONS was introduced in CMake 3.14.
if(CMAKE_VERSION VERSION_LESS "3.14")
set(CMAKE_REQUIRED_LINK_OPTIONS "-static")
else()
set(CMAKE_REQUIRED_FLAGS "-static")
endif()
# Check that the compiler can build a simple application and statically link
# with libatomic.
check_c_source_compiles("${CheckLibAtomicCompiles_CODE}"
HAVE_LIBATOMIC_COMPILES_STATIC)
else()
set(HAVE_LIBATOMIC_COMPILES_STATIC
0
CACHE INTERNAL "" FORCE)
endif()
unset(CMAKE_REQUIRED_FLAGS)
unset(CMAKE_REQUIRED_LIBRARIES)
unset(CMAKE_REQUIRED_LINK_OPTIONS)
set(CheckGCCAtomicIntrinsics_CODE
"
#include<stddef.h>
#include<stdint.h>
int main(void)
{
ptrdiff_t x = 0;
intmax_t y = 0;
__atomic_add_fetch(&x, 1, __ATOMIC_SEQ_CST);
__atomic_add_fetch(&y, 1, __ATOMIC_SEQ_CST);
return __atomic_sub_fetch(&x, 1, __ATOMIC_SEQ_CST)
+ __atomic_sub_fetch(&y, 1, __ATOMIC_SEQ_CST);
}
")
set(CMAKE_TRY_COMPILE_TARGET_TYPE EXECUTABLE) # CMake 3.6
check_c_source_compiles("${CheckGCCAtomicIntrinsics_CODE}"
HAVE_GCCATOMIC_INTRINSICS)
if(NOT HAVE_GCCATOMIC_INTRINSICS AND HAVE_LIBATOMIC)
set(CMAKE_REQUIRED_LIBRARIES "atomic")
check_c_source_compiles("${CheckGCCAtomicIntrinsics_CODE}"
HAVE_GCCATOMIC_INTRINSICS_REQUIRES_LIBATOMIC)
if(HAVE_GCCATOMIC_INTRINSICS_REQUIRES_LIBATOMIC)
set(HAVE_GCCATOMIC_INTRINSICS
1
CACHE INTERNAL "" FORCE)
endif()
endif()
endfunction(CheckGCCAtomicIntrinsics)
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