CMake link shared library(lib) on Windows but cannot find dll

When you're linking a shared library (lib) with CMake on Windows and encounter issues with finding the corresponding DLLs, there are a few steps you can take to resolve the problem:

1. Check DLL Locations: Make sure that the DLL files are located in a directory that's included in the system's PATH environment variable. If the DLLs are in the same directory as the executable, they should be found automatically.

2. CMake RPATH Configuration: CMake provides the CMAKE_INSTALL_RPATH and CMAKE_INSTALL_RPATH_USE_LINK_PATH variables that can help manage library paths. Set CMAKE_INSTALL_RPATH to the location where the DLLs will be at runtime. For example:

   cmakeCopy code
   set(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
   
   set(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
   
   

   This instructs the executable to look for DLLs in the same location as the linked libraries.

3. Copying DLLs: If the DLLs are not in the system PATH or the executable's directory, you can copy the required DLLs to the output directory during the build process. You can use CMake's add_custom_command to copy the DLLs. For example:

   cmakeCopy code
   add_custom_command(TARGET your_target POST_BUILD
   
                      COMMAND ${CMAKE_COMMAND} -E copy_if_different
   
                      "${CMAKE_BINARY_DIR}/path/to/dll.dll"
   
                      $<TARGET_FILE_DIR:your_target>)
   
   

   Replace "${CMAKE_BINARY_DIR}/path/to/dll.dll" with the actual path to the DLL and adjust your_target to the name of your target.

4. DLL Naming Conventions: Make sure that the DLL file name matches the library name specified in CMake. On Windows, DLLs usually have a lib prefix and a .dll extension. For example, if you're linking against mylib, the corresponding DLL should be named libmylib.dll.

5. Working Directory: When running the executable, ensure that the working directory is set to the location where the DLLs are located or that the DLLs are available in the system PATH.

By following these steps, you should be able to ensure that your program can find the required DLLs at runtime when linking a shared library with CMake on Windows.