c++ - 嵌套的静态链接库和一个怪异的错误

（平台：C ++ 14，Clang 3.8，Ubuntu 16.04，CMake 3.5.1）

我有两个静态库（PawLIB，CalikoCat）和一个依赖OtherLibrary的可执行文件。 CalkoCat中有一个单一类Dummy。（我只是确保在开始对该库进行认真开发之前，所有内容都正确链接。）

Dummy类当前依赖于PawLIB的功能进行测试。

calikocat-source/include/calikocat/dummy.hpp

#include "pawlib/iochannel.hpp"

class Dummy
{
    public:
        Dummy(){}
        static void speak();
        ~Dummy(){}
};

calikocat-source/src/dummy.cpp

#include "otherlibrary/dummy.hpp"

void Dummy::speak()
{
    pawlib::ioc << "Hello, world!" << pawlib::io_end;
}

没问题。它可以正确编译并与CMake链接。

注意：您可以放心地假设此问题中两个CMakeLists.txt文件中的所有变量都经过了仔细的测试和工作。我已经三遍了。

calikocat-source/CMakeLists.txt（摘要）

include_directories(include)

# Include headers of dependencies.
include_directories(${PAWLIB_DIR}/include)

add_library(${TARGET_NAME} STATIC
    include/calikocat/dummy.hpp
    src/dummy.cpp
)

# Link against dependencies.
target_link_libraries(${TARGET_NAME} ${PAWLIB_DIR}/lib/libpawlib.a)

现在，我喜欢在我的库中包含测试器应用程序，这也不例外。在回购中，我将库和测试程序代码分为calikocat-source和calikocat-tester目录。我也将CMake用于测试仪...

calikocat-tester/CMakeLists.txt（摘要）

include_directories(include)

# Include headers of dependencies.
include_directories(${PAWLIB_DIR}/include)
include_directories(../calikocat-source/include)

add_executable(calikocat-tester
    main.cpp
)

# Link against dependencies.
target_link_libraries(${TARGET_NAME} ${CPGF_DIR}/lib/libcpgf.a)
target_link_libraries(${TARGET_NAME} ${PAWLIB_DIR}/lib/libpawlib.a)
target_link_libraries(${TARGET_NAME} ${CMAKE_HOME_DIRECTORY}/../calikocat-source/lib/$<CONFIG>/libcalikocat.a)

这是否正确构建完全取决于main.cpp上是否存在一行！请仔细阅读以下内容。

calikocat-tester/main.cpp，工作版本

#include <calikocat/dummy.hpp>
#include <pawlib/iochannel.hpp>

int main()
{
    pawlib::ioc << "Hello, world!" << pawlib::io_end;
    Dummy::speak();

    return 0;
}

编译并运行此版本可按预期工作，将Hello, world!打印两次到终端。

calikocat-tester/main.cpp，非工作版本

#include <calikocat/dummy.hpp>
#include <pawlib/iochannel.hpp>

int main()
{
    //pawlib::ioc << "Hello, world!" << pawlib::io_end;
    Dummy::speak();

    return 0;
}

我无法直接使用PawLIB注释掉该文件的此版本。这是错误...

[100%] Linking CXX executable ../../bin/Debug/calikocat-tester
../../../calikocat-source/lib/Debug/libcalikocat.a(dummy.cpp.o): In function `Dummy::speak()':
/home/jason/Code/Repositories/calikocat/calikocat-source/src/dummy.cpp:4: undefined reference to `pawlib::ioc'
/home/jason/Code/Repositories/calikocat/calikocat-source/src/dummy.cpp:5: undefined reference to `pawlib::iochannel::operator<<(pawlib::ioformat::IOControl const&)'
../../../calikocat-source/lib/Debug/libcalikocat.a(dummy.cpp.o): In function `pawlib::iochannel::operator<<(char const*)':
/home/jason/Code/Repositories/calikocat/calikocat-source/../../pawlib/pawlib/include/pawlib/iochannel.hpp:521: undefined reference to `pawlib::iochannel::resolve_pointer(char const*)'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
CMakeFiles/calikocat-tester.dir/build.make:99: recipe for target '../../bin/Debug/calikocat-tester' failed

我希望它可以编译，并且在运行时，只需将Hello, world!打印到终端一次即可。

这是怎么回事，我想念什么？

最佳答案

您应该尝试反转这两行：

target_link_libraries(${TARGET_NAME} ${PAWLIB_DIR}/lib/libpawlib.a)
target_link_libraries(${TARGET_NAME} ${CMAKE_HOME_DIRECTORY}/../calikocat-source/lib/$<CONFIG>/libcalikocat.a)

因为libcalikocat.a使用的是libpawlib.a中的符号，所以它应该首先出现在命令行上。