How to link multiple libraries using CMake

Question

I have some code to do with DCMTK. I can successfully build and run it if I use g++ from the command line. This is the code:

#include "dcmtk/config/osconfig.h"
#include "dcmtk/dcmdata/dctk.h"

int main()
{
DcmFileFormat fileformat;
OFCondition status = fileformat.loadFile("test.dcm");
if (status.good())
{
   OFString patientsName;
   if (fileformat.getDataset()->findAndGetOFString(DCM_PatientsName, patientsName).good())
   {
      cout << "Patient's Name: " << patientsName << endl;
   } else
     cerr << "Error: cannot access Patient's Name!" << endl;
} else
cerr << "Error: cannot read DICOM file (" << status.text() << ")" << endl;
return 0;
}

This is the build command:

g++ testeapp.cxx -DHAVE_CONFIG_H -I/path_to_dcmtk/include -L/path_to_dcmtk/lib -pthread -ldcmdata -lz -loflog -lofstd -o main

I want to make a CMakeLists.txt to build it in Kdevelop. This is what I currently have:

    # Configure toplevel directories
    SET( PREFIX     ${CMAKE_INSTALL_PREFIX} CACHE PATH "Top level.")
    SET( INCLUDEDIR ${PREFIX}/include       CACHE PATH "Include files.")
    SET( LIBDIR     ${PREFIX}/lib           CACHE PATH "Libraries.")
    FIND_PACKAGE ( Threads REQUIRED )
    # Configure DCMTK
    FIND_PATH( DINIFTI_DCMTK_INCLUDE dcmtk
               PATHS ${INCLUDEDIR}
               PATH_SUFFIXES dcmtk
               DOC "Path to the DCMTK headers." )
    FIND_LIBRARY(DINIFTI_DCMTK_LIB NAMES dcmdata ofstd oflog 
                 HINTS ${LIBDIR} ${LIBDIR})
TARGET_LINK_LIBRARIES( dinifti ${DINIFTI_DCMTK_LIB}
                               ${DINIFTI_ZNZ_LIB}
                               ${CMAKE_THREAD_LIBS_INIT}
                               z )             

But when I build it, it has this error:

/usr/local/lib/libdcmdata.a(dcfilefo.o): In function `DcmFileFormat::remove(DcmItem*)':
dcfilefo.cc:(.text+0x1788): undefined reference to `log4cplus::Logger::forcedLog(int, OFString const&, char const*, int, char const*) const'

Can you help me to fix the error? Thank you.

Solution

It looks like you expect the find_library call to populate the variable DINIFTI_DCMTK_LIB with 3 separate libraries.

This isn't how find_library works. The different arguments after NAMES represent all the various names a single library could be called. This allows the command to work cross-platform, where the same library could be called different things on different platforms.

A minor issue is that you probably should prefer using PATHS instead of HINTS here. Form the docs:

... the HINTS option ... should be paths computed by system introspection, such as a hint provided by the location of another item already found. Hard-coded guesses should be specified with the PATHS option.

I imagine you want something more like:

find_library(DINIFTI_DCMTK_LIB NAMES dcmdata PATHS ${LIBDIR})
find_library(OFSTD_LIB NAMES ofstd PATHS ${LIBDIR})
find_library(OFLOG_LIB NAMES oflog PATHS ${LIBDIR})
target_link_libraries(dinifti ${DINIFTI_DCMTK_LIB}
                              ${OFLOG_LIB}
                              ${OFSTD_LIB}
                              ${DINIFTI_ZNZ_LIB}
                              ${CMAKE_THREAD_LIBS_INIT}
                              z)

Comments

[Angew is no longer proud of SO]

There is also a find module for DCMTK; perhaps find_package(DCMTK REQUIRED) would be of help?

[Fraser]

@Angew Good point, but the docs are a bit lacking :-)