如何通过cmake与-fPIC编译jsoncpp

Question

我想编译jsoncpp与-fPIC到cmake。

在jsoncpp的网站中，它通常会解释如下的编译方式。

mkdir -p build/debug 
cd build/debug 
cmake -DCMAKE_BUILD_TYPE=debug -DJSONCPP_LIB_BUILD_STATIC=ON -DJSONCPP_LIB_BUILD_SHARED=OFF -G "Unix Makefiles" ../.. 
make 

如何在此步骤中使用-fPIC标志进行编译？

--------------------------------------------- - - - - - - 编辑 - - - - - - - - - - - - - - - - - - - ----------------------

我假设我必须把一些行放在生成文件中-fPIC。

所以我通过cmake添加makefile的内容。

我怎样才能改变这个生成文件为-fPIC国旗？

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Answer 1

你必须改变CMAKE_CXX_FLAGS和CMAKE_CXX_FLAGS变量。你可以做到这一点通过ccmake或cmake-gui（你将不得不切换高级），或者你可以将它作为你在做：

cmake -DCMAKE_CXX_FLAGS=-fPIC -DCMAKE_C_FLAGS=-fPIC -DCMAKE_BUILD_TYPE=debug -DJSONCPP_LIB_BUILD_STATIC=ON -DJSONCPP_LIB_BUILD_SHARED=OFF -G "Unix Makefiles" ../.. 

不要刻意改变Makefile，因为它会被覆盖下一个你跑了cmake。

在CMake 2.8.9中，您可以在目标上设置POSITION_INDEPENDENT_CODE属性 以使所有跟随的目标位置独立。或者你也可以设置内的CMakeLists.txt

set(CMAKE_POSITION_INDEPENDENT_CODE ON) 

或

cmake -DCMAKE_POSITION_INDEPENDENT_CODE=ON ..