如何在CMake的try_compile函数中为OpenMP设置链接器标志 [英] How to set linker flags for OpenMP in CMake's try_compile function

问题描述

我想验证当前编译器是否可以使用openmp支持进行构建。应用程序已经部署在各种各样的unix系统上，其中一些可能有旧版本的OpenMP，我想测试重要的OpenMP功能。所以，我想构建一个包含一些OpenMP调用的测试源文件。

I would like to verify that the current compiler can build with openmp support. The application has do deploy across a wide variety of unix systems, some of which might have old versions of OpenMP, and I would like to test for important OpenMP functionality. So, I want to build a test source file that incorporates some of the OpenMP calls.

因此，我创建了一个非常简单的测试文件，并尝试使用try_compile函数从CMake。不幸的是，它似乎没有正确应用-fopenmp链接器标志。有没有人知道如何强制链接器标志或看看链接器标志是否正在任何地方应用？

Thus, I created a very simple test file, and attempted to use the try_compile function from CMake. Ufortunately, it doesn't seem to apply the -fopenmp linker flag correctly. Does anyone know how to either force the linker flag or to see if the linker flag is being applied anywhere?

来自CMakeLists.txt

from CMakeLists.txt

try_compile(
    HAVE_OPENMP
    ${APBS_ROOT}/src/config
    ${APBS_ROOT}/src/config/omp_test.c
    CMAKE_FLAGS "-DCMAKE_C_FLAGS=-fopenmp -DCMAKE_EXE_LINKER_FLAGS=-fopenmp"
    OUTPUT_VARIABLE TRY_COMPILE_OUTPUT
    )

来自omp_test.c

from omp_test.c

#include <stdio.h>
#include <omp.h>

int main()
{
    int i;
    int threadID = 0;
    #pragma omp parallel for private(i, threadID)
    for(i = 0; i < 16; i++ )
    {
        threadID = omp_get_thread_num();
        #pragma omp critical
        {
            printf("Thread %d reporting\n", threadID);
        }
    }
    return 0;
}

结果输出为

Change Dir: src/config/CMakeFiles/CMakeTmp

Run Build Command:/usr/bin/make "cmTryCompileExec/fast"
/usr/bin/make -f CMakeFiles/cmTryCompileExec.dir/build.make CMakeFiles/cmTryCompileExec.dir/build
make[1]: Entering directory `src/config/CMakeFiles/CMakeTmp'
/usr/bin/cmake -E cmake_progress_report /data/work/source/apbs/src/config/CMakeFiles/CMakeTmp/CMakeFiles 1
Building C object CMakeFiles/cmTryCompileExec.dir/omp_test.c.o
/usr/bin/gcc    -o CMakeFiles/cmTryCompileExec.dir/omp_test.c.o   -c /data/work/source/apbs/src/config/omp_test.c
Linking C executable cmTryCompileExec
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTryCompileExec.dir/link.txt --verbose=1
/usr/bin/gcc         CMakeFiles/cmTryCompileExec.dir/omp_test.c.o  -o cmTryCompileExec -rdynamic 
CMakeFiles/cmTryCompileExec.dir/omp_test.c.o: In function `main':
omp_test.c:(.text+0x19): undefined reference to `omp_get_thread_num'
collect2: ld returned 1 exit status
make[1]: *** [cmTryCompileExec] Error 1
make[1]: Leaving directory `src/config/CMakeFiles/CMakeTmp'
make: *** [cmTryCompileExec/fast] Error 2

CMake Error at CMakeLists.txt:688 (message):
  Test OpenMP program would not build.  OpenMP disabled

当我尝试在命令行上编译测试程序时，它工作正常

When I try to compile the test program on the command line, it works fine

src/config$ gcc -fopenmp omp_test.c -o omp_test && ./omp_test
Thread 1 reporting
Thread 4 reporting
Thread 7 reporting
Thread 11 reporting
Thread 9 reporting
Thread 12 reporting
Thread 6 reporting
Thread 8 reporting
Thread 15 reporting
Thread 13 reporting
Thread 10 reporting
Thread 0 reporting
Thread 3 reporting
Thread 2 reporting
Thread 5 reporting
Thread 14 reporting

推荐答案

CMake有一个标准模块用于测试编译器是否支持OpenMP：

CMake has a standard module for testing if the compiler supports OpenMP:

find_package(OpenMP)
if (OPENMP_FOUND)
    set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${OpenMP_C_FLAGS}")
    set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}")
endif()

这篇关于如何在CMake的try_compile函数中为OpenMP设置链接器标志的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！