[CMake] static versus shared libraries with BUILD_SHARED_LIBS

[James Bigler]

I'm using CMake 2.4.3 on Linux.  When I do:

OPTION(TEEM_BUILD_SHARED_LIBS "Build Teem with shared libraries." OFF)
OPTION(BUILD_SHARED_LIBS ${TEEM_BUILD_SHARED_LIBS})

or

OPTION(BUILD_SHARED_LIBS "Build package with shared libraries." OFF)

and later:

     FIND_PACKAGE(PNG)
     IF(PNG_FOUND)
       ADD_DEFINITIONS(-DTEEM_PNG=1 ${PNG_DEFINITIONS})
       SET(TEEM_PNG_LIB ${PNG_LIBRARIES})
       SET(TEEM_PNG_IPATH ${PNG_INCLUDE_DIR})
     ENDIF(PNG_FOUND)

Now I see in my cmake configuration:

  PNG_LIBRARY                      /usr/lib64/libpng.so
  PNG_PNG_INCLUDE_DIR              /usr/include

My packages libraries are built static, but I'm pulling in shared 
versions of external libraries.

I also have a static version of the library:

libpng-devel              /usr/lib64/libpng.a
libpng-devel              /usr/lib64/libpng.so

Why did FIND_PACKAGE and eventually FIND_LIBRARY expand this to the full 
path and name of the library?

When I look at the build output I see a spurious -rdynamic instead of 
-static.

Linking C executable ../../bin/unu
cd /home/sci/bigler/pub/src/teem/octagon/src/bin && /usr/local/bin/cmake 
-P CMakeFiles/unu.dir/cmake_clean_target.cmake
cd /home/sci/bigler/pub/src/teem/octagon/src/bin && /usr/bin/gcc    -O3 
-DNDEBUG  -fPIC "CMakeFiles/unu.dir/unu.o"   -o ../../bin/unu -rdynamic 
-L/home/sci/bigler/pub/src/teem/octagon/bin -L/usr/lib64 -lteem -lbz2 
-lz -lpng -lz -lm 
-Wl,-rpath,/home/sci/bigler/pub/src/teem/octagon/bin:/usr/lib64

I've verified that if I pass -static instead of -rdynamic it does what I 
think it should.

Thanks,
James