尽管我已经用 C++ 开发应用程序大约两到三年了，但我从来不需要自己建立一个项目。大多数项目都是预先配置的，因此我从未学会自己做。此刻有空闲时间，我心想:“我要创建我自己的第一个 CMake C++ 项目”。

因为我知道我想在数据库中存储信息，所以我开始创建一个简单的 CMake 项目，其中一个可执行文件链接到 MySQL Connector for C++，但立即失败了...

由于我 - 奇怪的是 - 在其他地方找不到有用的信息，我希望你们中的一个人可以成为我的救星。

我的项目设置如下:

Root 
- CMakeLists.txt 
- build 
- src 
- tests 
-- main.cpp 
- include 
-- mysql_connection.h 
-- cppconn 
--- driver.h 
--- exception.h 
--- resultset.h 
--- statement.h 
--- ... 
-- ... 
- libs 
-- libmysqlcppconn.dylib -> libmysqlcppconn.7.8.0.12.dylib (symlink) 
-- libmysqlcppconn.7.8.0.12.dylib 
-- libmysqlcppconn8.1.8.0.12.dylib 
-- libmysqlcppconn8.1.dylib  -> libmysqlcppconn8.1.8.0.12.dylib (symlink) 
-- libmysqlcppconn8.dylib -> libmysqlcppconn8.1.8.0.12.dylib (symlink) 
-- libssl.dylib 
-- libcrypto.dylib 
-- ... 

我的main.cpp包含:

#include "mysql_connection.h" 
#include <cppconn/driver.h> 
#include <cppconn/exception.h>  
#include <cppconn/resultset.h> 
#include <cppconn/statement.h> 
 
int main(int argc, char const *argv[]) 
{ 
    sql::Driver *driver; 
    sql::Connection *con; 
 
    driver = get_driver_instance(); 
    con = driver->connect("tcp://127.0.0.1:3306","root","securepw"); 
    return 0; 
} 

还有我的CMakeLists.txt:

cmake_minimum_required(VERSION 3.0) 
project(EconSim) 
 
add_executable(EconSim ${PROJECT_SOURCE_DIR}/tests/main.cpp) 
target_include_directories(EconSim PUBLIC ${PROJECT_SOURCE_DIR}/include) 
target_link_libraries(EconSim ${PROJECT_SOURCE_DIR}/libs/libmysqlcppconn.dylib) 
target_compile_features(EconSim PUBLIC cxx_std_17) 

我能够编译该应用程序，但在执行时出现以下错误:

dyld: Library not loaded: libmysqlcppconn.7.dylib 
  Referenced from: /Users/aosterthun/Documents/Programming/EconSim/build/./EconSim 
  Reason: image not found 
Abort trap: 6 

当在 CMakeLists.txt 中使用 libmysqlcppconn8.dylib 时: 还有我的 CMakeLists.txt:

cmake_minimum_required(VERSION 3.0) 
project(EconSim) 
 
add_executable(EconSim ${PROJECT_SOURCE_DIR}/tests/main.cpp) 
target_include_directories(EconSim PUBLIC ${PROJECT_SOURCE_DIR}/include) 
target_link_libraries(EconSim ${PROJECT_SOURCE_DIR}/libs/libmysqlcppconn8.dylib) 
target_compile_features(EconSim PUBLIC cxx_std_17) 

我收到编译错误:

[build] Starting build 
[proc] Executing command: /usr/local/bin/cmake --build /Users/aosterthun/Documents/Programming/EconSim/build --config Debug --target all -- -j 6 
[build] [ 50%] Linking CXX executable EconSim 
[build] Undefined symbols for architecture x86_64: 
[build]   "_get_driver_instance", referenced from: 
[build]       _main in main.cpp.o 
[build] ld: symbol(s) not found for architecture x86_64 
[build] clang: error: linker command failed with exit code 1 (use -v to see invocation) 
[build] make[2]: *** [EconSim] Error 1 
[build] make[1]: *** [CMakeFiles/EconSim.dir/all] Error 2 
[build] make: *** [all] Error 2 
[build] Build finished with exit code 2 

我发现了这个:How do I link C++ MySQL Connector Libraries to Cmake?但遗憾的是这并没有解决我的问题。

我还发现了CLion: undefined “_get_driver_instance”这导致了这个CMakeLists.txt:

cmake_minimum_required(VERSION 3.0) 
project(EconSim) 
 
include_directories(${PROJECT_SOURCE_DIR}/include) 
add_library(libmysqlcppconn STATIC IMPORTED) 
 
add_executable(EconSim ${PROJECT_SOURCE_DIR}/tests/main.cpp) 
set_property(TARGET libmysqlcppconn PROPERTY IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/libs/libmysqlcppconn-static.a) 
target_compile_features(EconSim PUBLIC cxx_std_17) 
target_link_libraries(EconSim libmysqlcppconn) 

这会导致此错误:

[build] Starting build 
[proc] Executing command: /usr/local/bin/cmake --build /Users/aosterthun/Documents/Programming/EconSim/build --config Debug --target all -- -j 6 
[build] [ 50%] Linking CXX executable EconSim 
[build] Undefined symbols for architecture x86_64: 
[build]   "_BIO_free", referenced from: 
[build]       sha256_password_auth_client(MYSQL_PLUGIN_VIO*, MYSQL*) in libmysqlcppconn-static.a(client_authentication.cc.o) 
[build]       caching_sha2_password_auth_client(MYSQL_PLUGIN_VIO*, MYSQL*) in libmysqlcppconn-static.a(client_authentication.cc.o) 
[build]   "_BIO_new_bio_pair", referenced from: 
[build]       dummy_function_needed_by_xplugin() in libmysqlcppconn-static.a(my_aes_openssl.cc.o) 
[build]   "_BIO_new_mem_buf", referenced from: 
[build]       sha256_password_auth_client(MYSQL_PLUGIN_VIO*, MYSQL*) in libmysqlcppconn-static.a(client_authentication.cc.o) 
[build]       caching_sha2_password_auth_client(MYSQL_PLUGIN_VIO*, MYSQL*) in libmysqlcppconn-static.a(client_authentication.cc.o) 
[build]   "_BN_bin2bn", refer... 

如果有任何帮助，我将不胜感激。甚至我还没有找到一个明显的解决方案的提示。我仍然有点困惑为什么我没有找到有关该主题的有用信息。因为应该有很多人使用这项技术进行开发。

如果我遗漏了任何信息，请询问更多信息。

请您参考如下方法:

您需要安装 openssl 和链接库 libcrypto、libssl、libresolv。 我解决这个问题的方法如下:

target_link_libraries(${PROJECT_NAME} 
PUBLIC 
    mysqlclient 
    mysqlcppconn-static 
    crypto 
    ssl 
    resolv 
)