[CMake] How to regenerate source file during make?

[Marcel Loose]

On Fri, 2010-01-15 at 10:07 -0500, David Cole wrote:
> On Fri, Jan 15, 2010 at 9:44 AM, Marcel Loose <loose at astron.nl> wrote:
>         Hi Jack,
>         
>         The difference with your and my case is that you have an input
>         file
>         (the .xsd file) and output files (the .h and .cpp files). In
>         my case I
>         generate the output file, e.g. myheader.h, from myheader.h.in,
>         using
>         configure_file(). The problem is that I cannot get this to
>         work during
>         'make', only during 'cmake'.
>         
>         Best regards,
>         Marcel Loose.
>         
>         On Fri, 2010-01-15 at 15:04 +0100, Smith Jack (Ext. - UGIS -
>         UniCredit
>         
>         Group) wrote:
>         > I do a similar thing with an XSD file from which I generate
>         c++
>         wrapper classes for accessing the corresponding XML
>         >
>         > Note the DEPENDS line !
>         >
>         > MACRO(XSD FILE NAMESPACE)
>         >     ADD_CUSTOM_COMMAND(
>         >         OUTPUT  ${CMAKE_CURRENT_SOURCE_DIR}/xml/${FILE}.cpp
>         >         OUTPUT  ${CMAKE_CURRENT_SOURCE_DIR}/xml/${FILE}.h
>         >         DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/xml/${FILE}.xsd
>         >         COMMAND ${XAPI_CODESYNTH}/bin/xsd
>         >         ARGS cxx-tree --generate-serialization
>         --hxx-suffix .h
>         --cxx-suffix .cpp --fwd-suffix -fwd.hxx --type-naming java
>         --function-naming java --namespace-map =${NAMESPACE}
>         --generate-polymorphic --output-dir
>         ${CMAKE_CURRENT_SOURCE_DIR}/xml
>         ${CMAKE_CURRENT_SOURCE_DIR}/xml/${FILE}.xsd
>         >         COMMENT "generating Codesynthesis Wrappers")
>         > ENDMACRO(XSD)
>         >
>         >
>         >
>         > > -----Original Message-----
>         > > From: cmake-bounces at cmake.org
>         > > [mailto:cmake-bounces at cmake.org] On Behalf Of Marcel Loose
>         > > Sent: Friday, January 15, 2010 2:55 PM
>         > > To: cmake at cmake.org
>         > > Subject: [CMake] How to regenerate source file during
>         make?
>         > >
>         > > Hi all,
>         > >
>         > > I've been struggling with this for hours now and I can't
>         seem
>         > > to get a grip on it.
>         > >
>         > > I have a header file that must be (re)generated during
>         'make'
>         > > when some external data have changed. I can successfully
>         > > generate this file during 'cmake' using configure_file(),
>         but
>         > > I haven't been able to figure out how I can trigger the
>         > > configure_file() during make.
>         > >
>         > > Should I define a target for this header file? Or can I
>         > > specify some kind of file dependency, such that when the
>         > > header file is missing our out-of-date, it will be
>         (re)generated?
>         > >
>         > > I guess it must be some clever combination of
>         > > add_custom_command() and add_custom_target().
>         > >
>         > > Best regards,
>         > > Marcel Loose.
>         
> 
> 
> This should work already: if you change my_header.h.in then cmake
> should re-run to re-configure your file at 'make' time.
> 
> 
> If you have additional dependencies that should trigger a
> re-configure, you should probably convert it to an add_custom_command
> such that it happens at build time.

It's not the myheader.h.in that's changing; myheader.h should be
regenerated because the value of one of the variables in myheader.h.in
(that get expanded) change. 

To be more precise, I try to record the svn revision number (and some
more svn info). I carefully read
http://www.mail-archive.com/cmake@cmake.org/msg25922.html, because it
closely matches my problem, but I couldn't figure out what
update_version.cmake should do exactly. In my case, I would need the
values of a number CMake variables (like CMAKE_CURRENT_BINARY_DIR), but
of course, these values are not around anymore when running 'make'.
Should all these variables be passed using -D?

Best regards,
Marcel Loose.