[CMake] FIND_LIBRARY - always true - very strange...

[Brad King]

Christian Kienle wrote:
> Hi all,
> 
> I have a strange problem - see my CMakeLists.txt file:
> 
>       1 PROJECT(LIBLOADER)
>       2
>       3 # let's look for libdl (libloader needs this for dlopen()  and 
> so on.
>       4 FIND_LIBRARY(PATH_OF_LIB_DL NAMES dadfdfasdf PATHS /usr/lib)
>       5 MESSAGE("-- checking for aNiceLib... ${PATH_OF_LIB_DL}")
>       6 IF (PATH_OF_LIB_DL)
>       7         MESSAGE("FOUND")
>       8 ELSE (PATH_OF_LIB_DL)
>       9         MESSAGE("-- error: libdl not found.")
>      10 ENDIF (PATH_OF_LIB_DL)
> 
> If I execute cmake . in my source directory I get this:
> 
> cmks-Computer:~/Desktop/cmksql/libloader cmk$ cmake .
> -- Check for working C compiler: gcc -- works
> -- Check for working CXX compiler: c++ -- works
> -- checking for aNiceLib... /usr/lib/libdl.dylib
> FOUND
> -- Configuring done
> -- Generating done
> -- Build files have been written to: /Users/cmk/Desktop/cmksql/libloader
> 
> But why did cmake found "dadfdfasdf"? It's not there... :/

Change your message command to

MESSAGE("FOUND: [${PATH_OF_LIB_DL}]")

and the problem will become clear.  Since you are not doing an 
out-of-source build the CMakeCache.txt in your source tree is being 
used.  It is leftover from some previous run in which your library name 
was found.  Once FIND_LIBRARY finds a library it saves the result in the 
variable given so that it does not have to search again.  This is the 
idea of the cache.

-Brad