[CMake] check_include_files() can't "find" header because it can't compile test app

[Casey Jones]

On Tuesday 15 September 2009 11:43:04 am Alexander Neundorf wrote:
> On Tuesday 15 September 2009, Casey Jones wrote:
> > On Monday 14 September 2009 3:22:14 pm Alexander Neundorf wrote:
> > > On Sunday 13 September 2009, Casey Jones wrote:
> > > > Hello, I'm trying to link a Qt4 library into my program as an
> > > > optional dependency.  I can get it to find and link the library with
> > > > a FindFoo.cmake. But when I use check_include_files( foo.h HAVE_FOO_H
> > > > ) it says it can't find the header.  So looking in CMakeError.log it
> > > > says it found foo.h but since it includes Qt headers like:
> > > > #include <QString>
> > > > instead of
> > > > #include <qt4/QtCore/QString>
> > > > it can't compile the test program.
> > > >
> > > > Is there a way to have check_include_files() not compile the test
> > > > program and just make sure the header exists?
> > >
> > > You could just use find_path(FOO_INCLUDE_DIR foo.h ...), usually this
> > > is good. enough.
> > > Or you can set the cmake variable CMAKE_REQUIRED_INCLUDES before
> > > calling the check_include_files() macro so that it lists all necessary
> > > include dirs (should be ${QT_QTCORE_INCLUDE_DIR} or something like
> > > this)
> > >
> > > > Or is there some other way to create the config.h.in and config.h?
> > >
> > > You don't *have* to compile anything in order to create a config.h from
> > > a config.h.in.
> > > configure_file() reads the config.h.in and replaces all cmake variables
> > >  with their values in that file and writes the output file.
> > > It doesn't matter where these values come from, whether a
> > > check_include_files() or if you just set them.
> > >
> > > Alex
> >
> > I'm trying out FIND_PATH(), but how do I put that variable into
> > config.h.in? I have the variable HAVE_FOO_H, and it finds the header, but
> > I just don't know what to do with that variable.
> >
> > Would I need to do something like:
> > IF( ${HAVE_FOO_H} )
> > 	WRITE_TO_FILE(src/config.h.in "#cmakedefine HAVE_FOO_H"
> > ENDIF( ${HAVE_FOO_H} )
> >
> > I don't know if the write_to_file function exists or not, so thats why
> > I'm asking.
> 
> You should write a file like e.g. "myheader.h.in", which could look like
>  that:
> 
> #define GREETING_TEXT "@MY_MESSAGE@"
> 
> #cmakedefine HAVE_FOO_H 1
> 
> 
> Then in your CMakeLists.txt you do:
> 
> set(MY_MESSAGE "Hello world")
> set(HAVE_FOO_H TRUE)
> 
> configure_file(myheader.h.in ${CMAKE_CURRENT_BINARY_DIR}/config.h)
> 
> This will make cmake read the existing myheader.h.in, replace the
>  @MY_MESSAGE@ with the contents of the cmake variable with the same name,
>  and turn the line with #cmakedefine either to
> #define HAVE_FOO_H 1
> (if the cmake variable HAVE_FOO_H is true) or to
> #undefine HAVE_FOO_H
> (if the cmake variable HAVE_FOO_H is not true).
> 
> HTH
> Alex
> 

Thanks.  I just added #cmakedefine HAVE_FOO_H to config.h.in, and used 
FIND_PATH() to set the variable.

Also, sorry about that last reply.  Apparently I forgot to change the "To" 
field so I sent it to your email and not the cmake list.

Casey