Boost.Test 链接器错误与预编译头文件 (PCH) 一起使用

Question

在使用带有预编译头 (PCH) 的 Boost.Test 时出现链接器错误，如果没有 PCH，该错误不会发生。我使用Usage variants 中描述的动态链接库。 如何修复错误以将 Boost.Test 也与 PCH 一起使用？

问题至少出现在 Fedora 和 boost 1.73（只有动态库）和 g++ 10/clang 11 中。

    $ cmake ../ && make
    -- Configuring done
    -- Generating done
    -- Build files have been written to: /home/.../boost_test_pch/build
    [ 33%] Building CXX object CMakeFiles/boost_utf_pch.dir/test_driver.cpp.o
    [ 66%] Building CXX object CMakeFiles/boost_utf_pch.dir/test.cpp.o
    [100%] Linking CXX executable boost_utf_pch
    [100%] Built target boost_utf_pch

对比

    $ cmake -DEDA_ENABLE_PCH=TRUE ../ && make
    -- Configuring done
    -- Generating done
    -- Build files have been written to: /home/.../boost_test_pch/build
    [ 25%] Building CXX object CMakeFiles/boost_utf_pch.dir/cmake_pch.hxx.gch
    [ 50%] Building CXX object CMakeFiles/boost_utf_pch.dir/test_driver.cpp.o
    cc1plus: warning: /home/.../boost_test_pch/build/CMakeFiles/boost_utf_pch.dir/cmake_pch.hxx.gch: not used because `BOOST_TEST_DYN_LINK' is defined [-Winvalid-pch]
    [ 75%] Building CXX object CMakeFiles/boost_utf_pch.dir/test.cpp.o
    [100%] Linking CXX executable boost_utf_pch
    /usr/bin/ld: /usr/lib/gcc/x86_64-redhat-linux/10/../../../../lib64/crt1.o: in function `_start':
    (.text+0x24): undefined reference to `main'
    collect2: error: ld returned 1 exit status
    make[2]: *** [CMakeFiles/boost_utf_pch.dir/build.make:138: boost_utf_pch] Error 1
    make[1]: *** [CMakeFiles/Makefile2:95: CMakeFiles/boost_utf_pch.dir/all] Error 2
    make: *** [Makefile:103: all] Error 2

我对之前的警告信息无能为力...

这里是操场文件：

• CMakeLists.txt：

    project(boost_utf_pch LANGUAGES CXX)
    cmake_minimum_required(VERSION 3.18)
  
    add_executable(${PROJECT_NAME} "")
  
    find_package(Boost 1.73.0 REQUIRED COMPONENTS 
        unit_test_framework)
  
    target_sources(${PROJECT_NAME} PRIVATE
        test_driver.cpp test.cpp)
    target_link_libraries(${PROJECT_NAME} PRIVATE
        Boost::unit_test_framework)
  
    set_source_files_properties(test_driver.cpp
        APPEND PROPERTIES COMPILE_DEFINITIONS "BOOST_TEST_DYN_LINK")
  
    option(EDA_ENABLE_PCH "Enable PCH" OFF)
    if (EDA_ENABLE_PCH)
        target_precompile_headers(${PROJECT_NAME} PRIVATE pch.hpp)
    endif()
  

• pch.hpp

    #pragma once
    #include <boost/test/unit_test.hpp>
  

• test.cpp

    #include <boost/test/unit_test.hpp>
  
    BOOST_AUTO_TEST_SUITE( my_test )
  
    BOOST_AUTO_TEST_CASE( test_case1 )
    {
      BOOST_TEST_WARN( sizeof(int) < 4U );
    }
  
    BOOST_AUTO_TEST_SUITE_END()
  

• test_driver.cpp

    #define BOOST_TEST_MODULE "Boost.UTF PCH Test Suite"
    #include <boost/test/unit_test.hpp>
  

Answer 1

Alan Birtles 得到了正确方向的提示。我不知道编译器开关 BOOST_TEST_DYN_LINK 对 PCH 上下文中单个文件的影响。项目所有文件的定义，格式为：

    target_compile_definitions(${PROJECT_NAME} PRIVATE
        "BOOST_TEST_DYN_LINK")  

无法理解并不能解决问题。只有在为驱动程序“main”设置属性SKIP_PRECOMPILE_HEADERS 后，它才能按预期编译和链接：

    project(boost_utf_pch LANGUAGES CXX)
    cmake_minimum_required(VERSION 3.18)

    add_executable(${PROJECT_NAME} "")

    find_package(Boost 1.73.0 REQUIRED COMPONENTS 
        unit_test_framework)

    target_sources(${PROJECT_NAME} PRIVATE
        test_driver.cpp test.cpp)

    target_link_libraries(${PROJECT_NAME} PRIVATE
        Boost::unit_test_framework)

    set_source_files_properties(test_driver.cpp
        APPEND PROPERTIES COMPILE_DEFINITIONS "BOOST_TEST_DYN_LINK")
    set_source_files_properties(test_driver.cpp
        PROPERTIES SKIP_PRECOMPILE_HEADERS ON)
        
    option(EDA_ENABLE_PCH "Enable PCH" ON)

    if (EDA_ENABLE_PCH)
        target_precompile_headers(${PROJECT_NAME} PRIVATE pch.hpp)
    endif()