making conditions for linux and windows when linking libraries

Question

Hello,

Windows VC++ 2008
linux gcc 4.4.3

I have the following problem. When I compile on windows I need the ws2_32 library. However, when I compile on linux, I don't need to link this.

My CMakeLists.txt

INCLUDE_DIRECTORIES($CLIENT_SERVER_SOURCE_DIR/client)
INCLUDE_DIRECTORIES($CLIENT_SERVER_SOURCE_DIR/cltsvr_ults)

# Link the library
LINK_DIRECTORIES($CLIENT_SERVER_DIR/client)

# Add the executable 
ADD_EXECUTABLE(clt test_clt)

# Link the executable to the client library
IF(WIN32)
    TARGET_LINK_LIBRARIES(clt client ws2_32)
ENDIF(WIN32)

IF(CMAKE_COMPILER_IS_GNUCXXX)
  TARGET_LINK_LIBRARIES(clt client)
ENDIF(CMAKE_COMPILER_IS_GNUCXXX)

I have tried unsuccessfully to compile under linux. Using the above conditions. However, It always tries to link the ws2_32 and I get a compile error. I think that the conditions aren't working, as it always falls through the WIN32 condition.

many thanks for any suggestions,

Answer 1

Since the WIN32 thing is such a fundamental part of CMake, I'd guess that there is more to this than what you mention.

Are you doing a clean check out of your code, or just copying up a whole directory on Linux? If you have all your CMake build files cached from the Windows build, maybe (just maybe!) something has snuck in there and "detects" itself as WIN32 on Linux?

Are you sure it is that line and not something else that causes the link to the stray Win-library? Maybe try a MESSAGE(STATUS "I am here")line within the IF(WIN32) just to make sure.

Are you sure the error is caused by linking that library? I can see a typo in your script, it should be IF(CMAKE_COMPILER_IS_GNUCXX) - you have an extra X on there. Perhaps you are not linking in what you thing you are, and that is why it fails.