如何修改CMake生成的链接命令中的-Ldir1为-Ldir2？

Hey there, let’s work through this library path issue you’re facing—where your CMake-generated Makefile is using -Ldir1 instead of -Ldir2 during linking, even with devtoolset-3 installed. Here’s a step-by-step breakdown of how to resolve this:

1. Track Down Where dir1 Is Coming From #

First, we need to pinpoint why CMake is picking up dir1 in the first place. Devtoolset-3 sets environment variables that can influence CMake’s library search logic, so let’s check those:

• Activate devtoolset-3 with scl enable devtoolset-3 bash
• Run these commands to see if dir1 appears in library-related environment variables:

  echo $LIBRARY_PATH
  echo $LD_LIBRARY_PATH
  echo $CMAKE_LIBRARY_PATH
  

If dir1 shows up in any of these, that’s almost certainly the source of your problem.

2. Explicitly Set the Correct Path in CMakeLists.txt (Most Reliable) #

The most foolproof way to ensure CMake uses dir2 is to specify it directly in your CMakeLists.txt. This avoids relying on environment variables entirely:

• Use find_library to locate your library in dir2 (preferred over link_directories for better portability):

  # Replace "mylib" with your actual library name
  find_library(TARGET_LIB NAMES mylib PATHS /path/to/dir2 NO_DEFAULT_PATH)
  # Link the library to your target executable
  target_link_libraries(your_executable_name ${TARGET_LIB})
  

• Alternatively, if you need to add dir2 as a general search path for multiple libraries:

  link_directories(/path/to/dir2)
  

3. Override Paths via Environment Variables (For .bashrc Auto-Enable) #

If you want this to work automatically like devtoolset-3 does, set the CMAKE_LIBRARY_PATH environment variable in your .bashrc—CMake prioritizes this variable when searching for libraries:

• Add this line to ~/.bashrc:

  export CMAKE_LIBRARY_PATH=/path/to/dir2:$CMAKE_LIBRARY_PATH
  

• Reload your .bashrc with source ~/.bashrc, then clear CMake’s cache and regenerate the Makefile:

  rm -f CMakeCache.txt
  rm -rf CMakeFiles
  ccmake ..
  make
  

4. Adjust Devtoolset-3’s Environment Variables #

If devtoolset-3’s activation script is adding dir1 to your library paths, you can override this in .bashrc immediately after loading devtoolset’s config:

• Add these lines to ~/.bashrc:

  # Activate devtoolset-3
  source /opt/rh/devtoolset-3/enable
  # Prepend dir2 to library paths to prioritize it over dir1
  export LIBRARY_PATH=/path/to/dir2:$LIBRARY_PATH
  export LD_LIBRARY_PATH=/path/to/dir2:$LD_LIBRARY_PATH
  

This ensures every time you open a terminal, dir2 is the first path searched for libraries.

5. Clear CMake’s Cache #

Don’t forget that CMake caches previous path settings, so even after making changes, you need to clear the cache to force it to pick up the new paths:

rm -f CMakeCache.txt
rm -rf CMakeFiles

Then re-run ccmake or cmake to generate a fresh Makefile.

内容的提问来源于stack exchange，提问作者sancho.s ReinstateMonicaCellio