Hey there! I’ve dealt with this exact headache when working on CMake projects in Visual Studio—having to re-run CMake every time you switch build configs is such a waste of time. Let’s get this fixed so VS automatically links the right libraries based on your active Debug/Release configuration.

The Root Problem #

Visual Studio is a multi-config generator, which means it handles all build configurations (Debug, Release, etc.) in a single CMake run. The old approach of setting separate variables for Debug/Release libraries and linking them statically only works if you re-run CMake for each config—we need a way to tell CMake to pass both library options to VS, so it picks the right one at build time.

Fix 1: Use Generator Expressions (Most Flexible) #

Generator expressions are evaluated at build time, not during CMake’s configuration step. This lets you define different libraries for each config in a single CMakeLists.txt, and VS will handle the rest.

Here’s how to modify your example code:

add_executable(App main.cpp)

# Link the appropriate library based on the active build configuration
target_link_libraries(App 
    PRIVATE
        $<$<CONFIG:Debug>:mylibd.lib>   # Debug config links mylibd.lib
        $<$<CONFIG:Release>:mylib.lib> # Release config links mylib.lib
)

If your debug/release libraries are in different directories, add the paths with generator expressions too:

add_executable(App main.cpp)

# Set library directories per configuration
target_link_directories(App
    PRIVATE
        $<$<CONFIG:Debug>:./libs/debug>   # Path to debug libraries
        $<$<CONFIG:Release>:./libs/release> # Path to release libraries
)

# Link the libraries (now CMake can find them in the correct directories)
target_link_libraries(App
    PRIVATE
        $<$<CONFIG:Debug>:mylibd>
        $<$<CONFIG:Release>:mylib>
)

Fix 2: Use CMAKE_DEBUG_POSTFIX (For Standard Naming) #

If your libraries follow a consistent naming pattern (e.g., mylib.lib for Release, mylibd.lib for Debug), you can use CMake’s built-in CMAKE_DEBUG_POSTFIX variable to simplify things:

# Set the debug suffix matching your library naming
set(CMAKE_DEBUG_POSTFIX "d")

add_executable(App main.cpp)

# Just link "mylib"—CMake automatically appends the suffix for Debug builds
target_link_libraries(App PRIVATE mylib)

This works because CMake will look for mylib${CMAKE_DEBUG_POSTFIX}.lib when building in Debug mode, and mylib.lib for Release. Make sure your library directories are properly set so CMake can locate both versions.

How to Verify It Works #

1. Save your modified CMakeLists.txt
2. Re-run CMake once to generate the VS project
3. Open the project in Visual Studio
4. Switch between Debug and Release configurations—you’ll notice the linked libraries update automatically without needing to re-run CMake!

内容的提问来源于stack exchange，提问作者Efrat