[CMake] How pass a -spec parameter to FindQt4.cmake?

[Daniel Näslund]

On Mon, Jul 18, 2011 at 07:23:26AM -0700, clinton at elemtech.com wrote:
> What version of cmake are you using? 

$ cmake --version
cmake version 2.8.4

> And since you are cross-compiling, what does your toolchain file for
> cmake look like?  

The contents of my toolchain.cmake file:

    set(CMAKE_SYSTEM_NAME Linux)
    set(CROSSPREFIX /opt/crosstool/gcc-4.2.0-glibc-2.5/powerpc-603-linux-gnu)

    set(CMAKE_C_COMPILER   ${CROSSPREFIX}/bin/powerpc-603-linux-gnu-gcc)
    set(CMAKE_CXX_COMPILER ${CROSSPREFIX}/bin/powerpc-603-linux-gnu-g++)
    set(CMAKE_LINKER       ${CROSSPREFIX}/bin/powerpc-603-linux-gnu-ld)

    set(CMAKE_FIND_ROOT_PATH ${CROSSPREFIX}/lib
                             /opt/env/lenny-ppc/lib
                             /opt/env/lenny-ppc/usr/lib)

    set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
    set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
    set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

The part of my CMakeLists.txt that tries to find a Qt installation:

    if (USE_QT)
        message(STATUS "Build support for QT is enabled.")
        find_package(Qt4 4.4 COMPONENTS QtCore QtDbus REQUIRED)
        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DHAS_QT")
        include(${QT_USE_FILE})
    else()
        message(STATUS "Build support for QT is disabled.")
    endif (HAS_QT)

> Did you add a find path in that file for your powerpc libs?  

Since the libs are located in /opt/env/lenny-ppc/usr/lib/qt4 I expect
that this line taken from the toolchain file above is sufficient:

    set(CMAKE_FIND_ROOT_PATH ${CROSSPREFIX}/lib
                             /opt/env/lenny-ppc/lib
                             /opt/env/lenny-ppc/usr/lib)

> The spec file only applies on qmake generated makefiles, which is not
> happening when using cmake.  

Ah, 

> And you do not need to build your own qmake.

Ok. But I don't see how I can make qmake return the right information.
Here's the function in FindQt4.cmake that is used for querying qmake:

    function(_QT4_QUERY_QMAKE VAR RESULT)
      exec_program(${QT_QMAKE_EXECUTABLE} ARGS "-query ${VAR}" RETURN_VALUE return_code OUTPUT_VARIABLE output )
      if(NOT return_code)
        file(TO_CMAKE_PATH "${output}" output)
        set(${RESULT} ${output} PARENT_SCOPE)
      endif(NOT return_code)
    endfunction(_QT4_QUERY_QMAKE)

I don't see anywhere that it relies upon some variable that I can change
in order to have it point at the target Qt4 installation. Is there some
global variable involved for setting the base directory or something
similar?

Daniel