[CMake] Need help using libraries in non-standard locations

[Bill Hoffman]

Guido W. wrote:
> Hi,
>
> I'm trying to write a CMakeLists.txt for a small program that needs to use the 
> Sybase client libraries. These libraries are often in different locations, on 
> my system they are in /opt/sybase/ase/OCS-15_0/lib. So, my first thought was 
> to write something like this:
>
> [...]
> ADD_LIBRARY (dbconns SHARED ${DBCONNS_SRC})
> FIND_LIBRARY (SYBLIB15 NAMES sybct PATHS 
> $ENV{SYBASE}/$ENV{SYBASE_OCS} /opt/sybase/OCS-15_0 /opt/sybase/ase/OCS-15_0 
> PATH_SUFFIXES /lib)
> IF(NOT SYBLIB15)
> 	MESSAGE (FATAL_ERROR "Sybase libraries not found")
> MESSAGE ("Sybase libraries found in ${SYBLIB15}")
> LINK_DIRECTORIES (${SYBLIB15})
> TARGET_LINK_LIBRARIES (dbconns sybtcl sybintl sybcomn sybct sybcs)
> [...]
>
> This didn't work. The output from that MESSAGE command was:
>
> Sybase libraries found in /opt/sybase/ase/OCS-15_0/lib/libsybct.so
>
> So, the output from FIND_LIBRARY was the complete path to the file I told it 
> to look for and not, as I was expecting, just the directory in which the file 
> was found. (BTW, why is that so? What am I to do with that output anyway? I 
> can't use it for either LINK_DIRECTORIES or TARGET_LINK_LIBRARIES...)
>
> Anyway, I went on to do something like this instead:
>
> [...]
> FIND_PATH (SYB15_LIBDIR libsybct.so PATHS 
> $ENV{SYBASE}/$ENV{SYBASE_OCS}/lib /opt/sybase/OCS-15_0/lib /opt/sybase/ase/OCS-15_0/lib)
> MESSAGE ("Sybase libraries found in ${SYB15_LIBDIR}")
> [...]
> LINK_DIRECTORIES (${SYB15_LIBDIR})
> [...]
>
> Okay, so this obviously sucks, because it's not portable and doesn't work with 
> static libraries.
> Also, it _still_ doesn't work - the compiler can't find the library when 
> linking.
> This is how the linker commandline looks like when running make VERBOSE=1:
>
> /usr/bin/c++  -fPIC    -shared -Wl,-soname,libdbconns.so -o libdbconns.so \ 
> "CMakeFiles/dbconns.dir/dbconn.o" "CMakeFiles/dbconns.dir/dbconnfactory.o" \ 
> "CMakeFiles/dbconns.dir/dbconnpg.o" "CMakeFiles/dbconns.dir/dbconnsyb.o" \ 
> -lsybtcl -lsybintl -lsybcomn -lsybct -lsybcs
> /usr/lib/gcc-lib/i586-suse-linux/3.3.5/../../../../i586-suse-linux/bin/ld: \ 
> cannot find -lsybtcl
> collect2: ld returned 1 exit status
>
> There is no -L or -Wl,-R anywhere in there. It looks like cmake is just 
> ignoring the LINK_DIRECTORIES command...
>
> Can anyone help me with this?
>   
You should be using the full path to the libraries in 
target_link_library.  The link_directories must come before the target 
is added for it to take effect.   But the full path should be used.  You 
can also add to where cmake search by setting the environment variable 
CMAKE_LIBRARY_PATH so it can find the libs you want.


-Bill