跨平台动态库导出符号最佳实现

定义良好的EXPORTED宏实现

#pragma once

#if defined _WIN32 || defined __CYGWIN__
  // Win32或者Cygwin
  #ifdef MYLIB_STATIC_DEFINE
    // 静态库
    #define MYLIB_EXPORT
    #define MYLIB_NO_EXPORT
  #elif
    // 动态库
    #ifdef MYLIB_EXPORTS
      // 库导出
      #ifdef __GNUC__
        #define MYLIB_EXPORT __attribute__ ((dllexport))
      #else
        #define MYLIB_EXPORT __declspec(dllexport)
      #endif
    #else
      // 用户库导入
      #ifdef __GNUC__
        #define MYLIB_EXPORT __attribute__ ((dllimport))
      #else
        #define MYLIB_EXPORT __declspec(dllimport)
      #endif
    #endif
  #endif
#else
  // Linux
  #ifdef MYLIB_STATIC_DEFINE
    // 静态库
    #define MYLIB_EXPORT
    #define MYLIB_NO_EXPORT
  #else
    // 动态库
    #ifdef MYLIB_EXPORTS
      #define MYLIB_EXPORT __attribute__ ((visibility ("default")))
      #define MYLIB_NO_EXPORT  __attribute__ ((visibility ("hidden")))
    #else
      #define MYLIB_EXPORT
      #define MYLIB_NO_EXPORT
    #endif
  #endif
#endif

CMake脚本示例

# CMakeLists.txt

# 设置cmake版本需求
cmake_minimum_required(VERSION 3.4)

set (PROJECT_VERSION "1.0")

# 定义项目名称并设定版本号，cmake自动解析MAJOR MINOR PATCH TWEAK[1]
project(mylib VERSION ${PROJECT_VERSION})

# 定义库名称
add_library(mylib SHARED)

# 添加源码
target_sources(mylib
  ${CMAKE_CURRENT_SOURCE_DIR}/main.cpp
)

# 设置库版本属性
set_target_properties(mylib
PROPERTIES
    VERSION ${PROJECT_VERSION}
    SOVERSION ${PROJECT_VERSION}
)

# 设置宏定义导出符号
target_compile_definitions(mylib PRIVATE mylib_EXPORT)

# 设置编译器选项
if (${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU")
    # G++ 默认所有符号隐藏[2]
    target_compile_options(mylib PRIVATE -Wall -Wextra "-fvisibility=hidden")
endif()

参考

1. https://cmake.org/cmake/help/v3.19/command/project.html ↩
2. https://cmake.org/cmake/help/v3.19/command/target_compile_options.html ↩