[CMake] how to use external gnu make library

[Jan Woetzel]

kdsfinger at gmail.com wrote:

> I am trying to use the gnu gsl package in vtk. The gsl is make 
> installed by gnu, not cmake. How can I use the library in my vtk 
> project? I put something like
> FIND_PACKAGE(GSL)

Does a "FindGSL.cmake" script exist and does cmake find it?
See the cmake  FIND_PACKAGE help.

As far as I know CMake does not come with a "standard" find script for
GSL, thus you have to write one yourself .
The CMake "Modules" directory contains examples.

We already created our own simple GSL find, see teh attached file.
It is simply based on "gsl-config", actually and works only on Linux.

Jan.

-- 

   Dipl.-Ing. Jan Woetzel
--------------------------------------------------
   Uni Kiel
   Institut f. Informatik und Praktische Mathematik
   Hermann-Rodewaldstr. 3  [Raum 310]
   24098 Kiel/Germany
--------------------------------------------------
   Tel    +49-431-880-4477
   Fax    +49-431-880-4054
   Privat +49-431-802872
   Mob.   +49-179-2937346
--------------------------------------------------
   Url    www.mip.informatik.uni-kiel.de/~jw
   Email  jw at mip.informatik.uni-kiel.de
   Privat jw at WoetzelWeb.de


-------------- next part --------------
## 
## Try to find gnu scientific library GSL  
## (see http://www.gnu.org/software/gsl/)
## Once run this will define: 
## 
## GSL_FOUND       = system has GSL lib
##
## GSL_LIBRARIES   = full path to the libraries
##    on Unix/Linux with additional linker flags from "gsl-config --libs"
## 
## CMAKE_GSL_CXX_FLAGS  = Unix compiler flags for GSL, essentially "`gsl-config --cxxflags`"
##
## GSL_INCLUDE_DIR      = where to find headers 
##
## GSL_LINK_DIRECTORIES = link directories, useful for rpath on Unix
## GSL_EXE_LINKER_FLAGS = rpath on Unix
##
## Felix Woelk 07/2004
## minor corrections Jan Woetzel
##
## www.mip.informatik.uni-kiel.de
## --------------------------------

IF(WIN32)
  MESSAGE(SEND_ERROR "FindGSL.cmake: gnu scientific library GSL not (yet) supported on WIN32")
  
ELSE(WIN32)
  IF(UNIX) 
    SET(GSL_CONFIG_PREFER_PATH "$ENV{GSL_HOME}/bin" CACHE STRING "preferred path to OpenSG (osg-config)")
    FIND_PROGRAM(GSL_CONFIG gsl-config
      ${GSL_CONFIG_PREFER_PATH}
      /usr/bin/
      )
    # MESSAGE("DBG GSL_CONFIG ${GSL_CONFIG}")
    
    IF (GSL_CONFIG) 
      # set CXXFLAGS to be fed into CXX_FLAGS by the user:
      SET(GSL_CXX_FLAGS "`${GSL_CONFIG} --cflags`")
      
      # set INCLUDE_DIRS to prefix+include
      EXEC_PROGRAM(${GSL_CONFIG}
        ARGS --prefix
        OUTPUT_VARIABLE GSL_PREFIX)
      SET(GSL_INCLUDE_DIR ${GSL_PREFIX}/include CACHE STRING INTERNAL)

      # set link libraries and link flags
      SET(GSL_LIBRARIES "`${GSL_CONFIG} --libs`")
      
      ## extract link dirs for rpath  
      EXEC_PROGRAM(${GSL_CONFIG}
        ARGS --libs
        OUTPUT_VARIABLE GSL_CONFIG_LIBS )

      ## split off the link dirs (for rpath)
      ## use regular expression to match wildcard equivalent "-L*<endchar>"
      ## with <endchar> is a space or a semicolon
      STRING(REGEX MATCHALL "[-][L]([^ ;])+" 
        GSL_LINK_DIRECTORIES_WITH_PREFIX 
        "${GSL_CONFIG_LIBS}" )
        #      MESSAGE("DBG  GSL_LINK_DIRECTORIES_WITH_PREFIX=${GSL_LINK_DIRECTORIES_WITH_PREFIX}")

      ## remove prefix -L because we need the pure directory for LINK_DIRECTORIES
      
      IF (GSL_LINK_DIRECTORIES_WITH_PREFIX)
        STRING(REGEX REPLACE "[-][L]" "" GSL_LINK_DIRECTORIES ${GSL_LINK_DIRECTORIES_WITH_PREFIX} )
      ENDIF (GSL_LINK_DIRECTORIES_WITH_PREFIX)
      SET(GSL_EXE_LINKER_FLAGS "-Wl,-rpath,${GSL_LINK_DIRECTORIES}" CACHE STRING INTERNAL)
      #      MESSAGE("DBG  GSL_LINK_DIRECTORIES=${GSL_LINK_DIRECTORIES}")
      #      MESSAGE("DBG  GSL_EXE_LINKER_FLAGS=${GSL_EXE_LINKER_FLAGS}")

      #      ADD_DEFINITIONS("-DHAVE_GSL")
      #      SET(GSL_DEFINITIONS "-DHAVE_GSL")
      MARK_AS_ADVANCED(
        GSL_CXX_FLAGS
        GSL_INCLUDE_DIR
        GSL_LIBRARIES
        GSL_LINK_DIRECTORIES
        GSL_DEFINITIONS
      )
      MESSAGE(STATUS "Using GSL from ${GSL_PREFIX}")
      
    ELSE(GSL_CONFIG)
      MESSAGE("FindGSL.cmake: gsl-config not found. Please set it manually. GSL_CONFIG=${GSL_CONFIG}")
    ENDIF(GSL_CONFIG)

  ENDIF(UNIX)
ENDIF(WIN32)


IF(GSL_LIBRARIES)
  IF(GSL_INCLUDE_DIR OR GSL_CXX_FLAGS)

    SET(GSL_FOUND 1)
    
  ENDIF(GSL_INCLUDE_DIR OR GSL_CXX_FLAGS)
ENDIF(GSL_LIBRARIES)