我正在尝试在Linux上使用cmake构建共享库。负责设置的代码部分是：
if (BUILD_SHARED)
set(BUILD_SHARED_LIBS ON)
set(CMAKE_VERBOSE_MAKEFILE ON)
# shared library
add_library(semsim SHARED "${SEMSIM_HEADERS}" "${SEMSIM_SOURCES}")
#Note: not sure if this command does anything. It was supposed to be to link static libraries into my shared one
# target_link_options(semsim PUBLIC -Wl,--whole-archive)
#
message(STATUS "LIBBZ_INCLUDE_DIR ${LIBBZ_INCLUDE_DIR}")
target_include_directories(semsim PUBLIC # make public so include dirs propagate into test binaries
${CMAKE_SOURCE_DIR}
${LIBXML2_INCLUDE_DIR}
${LIBSBML_DEPS_INCLUDE_DIR}
${LIBSBML_INCLUDE_DIR}
${ZLIB_INCLUDE_DIR}
${ZIPPER_INCLUDE_DIR}
${LIBCOMBINE_INCLUDE_DIR}
${BZ2_INCLUDE_DIR}
${REDLAND_INCLUDE_DIR}
${RASQAL_INCLUDE_DIR}
${RAPTOR2_INCLUDE_DIR}
)
target_link_libraries(semsim PUBLIC # make public so libraries propagate into test binaries
${LIBCOMBINE_STATIC_LIBRARY}
${ZIPPER_STATIC_LIBRARY}
${ZLIB_STATIC_LIBRARY}
${LIBSBML_STATIC_LIB}
${LIBBZ_STATIC_LIBRARY}
${REDLAND_LIBRARY}
${RASQAL_LIBRARY}
${RAPTOR2_LIBRARY}
${LIBXML2_STATIC_LIBRARY}
dl
${BZ2_STATIC_LIBRARY}
curl xslt
)
endif ()
这将产生以下执行命令：
/usr/bin/c++ -fPIC -std=c++14 -g -shared -Wl,-soname,libsemsim.so -o libsemsim.so CMakeFiles/semsim.dir/CurlGet.cpp.o CMakeFiles/semsim.dir/RDFNode.cpp.o CMakeFiles/semsim.dir/Subject.cpp.o CMakeFiles/semsim.dir/Predicate.cpp.o CMakeFiles/semsim.dir/Resource.cpp.o CMakeFiles/semsim.dir/Triple.cpp.o CMakeFiles/semsim.dir/SemsimUtils.cpp.o CMakeFiles/semsim.dir/MetaID.cpp.o CMakeFiles/semsim.dir/XmlAssistant.cpp.o CMakeFiles/semsim.dir/Reader.cpp.o CMakeFiles/semsim.dir/Editor.cpp.o CMakeFiles/semsim.dir/Writer.cpp.o CMakeFiles/semsim.dir/RDF.cpp.o CMakeFiles/semsim.dir/Participant.cpp.o CMakeFiles/semsim.dir/PhysicalEntity.cpp.o CMakeFiles/semsim.dir/PhysicalPhenomenon.cpp.o CMakeFiles/semsim.dir/PhysicalProcess.cpp.o CMakeFiles/semsim.dir/PhysicalPropertyResource.cpp.o CMakeFiles/semsim.dir/PhysicalForce.cpp.o CMakeFiles/semsim.dir/Query.cpp.o CMakeFiles/semsim.dir/SemsimCombineArchive.cpp.o CMakeFiles/semsim.dir/Triples.cpp.o ../../third_party/libCombine-0.2.3/INSTALL/lib/libCombine-static.a ../../third_party/zipper/INSTALL/lib/libZipper-static.a ../../third_party/zlib-1.2.11/INSTALL/lib/libz.a /usr/local/lib/libxml2.a -ldl ../../third_party/libsbml-dependencies/INSTALL/lib/libbz2.a -lcurl -lxslt
如果我让CMake尝试使用此命令进行构建，则会出现以下错误：
/usr/bin/ld: /usr/local/lib/libxml2.a(uri.o): relocation R_X86_64_PC32 against symbol `xmlFree' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
但是，我注意到CMake产生的命令缺少-L标志。所以我将命令更改为：
/usr/bin/c++ -fPIC -std=c++14 -g -shared -o libsemsim.so CMakeFiles/semsim.dir/CurlGet.cpp.o CMakeFiles/semsim.dir/RDFNode.cpp.o CMakeFiles/semsim.dir/Subject.cpp.o CMakeFiles/semsim.dir/Predicate.cpp.o CMakeFiles/semsim.dir/Resource.cpp.o CMakeFiles/semsim.dir/Triple.cpp.o CMakeFiles/semsim.dir/SemsimUtils.cpp.o CMakeFiles/semsim.dir/MetaID.cpp.o CMakeFiles/semsim.dir/XmlAssistant.cpp.o CMakeFiles/semsim.dir/Reader.cpp.o CMakeFiles/semsim.dir/Editor.cpp.o CMakeFiles/semsim.dir/Writer.cpp.o CMakeFiles/semsim.dir/RDF.cpp.o CMakeFiles/semsim.dir/Participant.cpp.o CMakeFiles/semsim.dir/PhysicalEntity.cpp.o CMakeFiles/semsim.dir/PhysicalPhenomenon.cpp.o CMakeFiles/semsim.dir/PhysicalProcess.cpp.o CMakeFiles/semsim.dir/PhysicalPropertyResource.cpp.o CMakeFiles/semsim.dir/PhysicalForce.cpp.o CMakeFiles/semsim.dir/Query.cpp.o CMakeFiles/semsim.dir/SemsimCombineArchive.cpp.o CMakeFiles/semsim.dir/Triples.cpp.o -L ../../third_party/libCombine-0.2.3/INSTALL/lib/libCombine-static.a -L ../../third_party/
zipper/INSTALL/lib/libZipper-static.a -L ../../third_party/zlib-1.2.11/INSTALL/lib/libz.a -L /usr/local/lib/libxml2.a -l
dl -L ../../third_party/libsbml-dependencies/INSTALL/lib/libbz2.a -lcurl -lxslt
在外壳中运行它，它可以正常工作。有人可以建议为什么CMake不在适当的地方使用-L标志吗？