[CMake] How to regenerate source file during make?

[Marcel Loose]

On Fri, 2010-01-15 at 16:35 +0100, Michael Wild wrote:
> On 15. Jan, 2010, at 16:25 , Marcel Loose wrote:
> 
> > 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.
> 
> You configure_file a CMake script at CMake time which you then use in
an add_custom_command to run at make-time. So you put all the "static"
data you need (such as CMAKE_BINARY_DIRECTORY, etc.) in the script file
and then you have them available at make time:
> 
> some_script.cmake:
> ------------------
> set(CMAKE_SOURCE_DIR "@CMAKE_SOURCE_DIR@")
> set(CMAKE_BINARY_DIR "@CMAKE_BINARY_DIR@")
> set(SVN_EXECUTABLE "@SVN_EXECUTABLE@")
> # ... do what you need to to ...
> -------------------
> 
> 
> But I still don't see why you have to extract version-information at
build time, because IMHO that shouldn't change between CMake-runs.
> 
> Michael
> 

Yes it can change between CMake runs. If, for example, I commit one or
two modified source files, there's no need to rerun cmake, and 'make'
will only rebuild those two sources (and the targets that depend on
them, of course). The version info has changed, though. However, the
header file containing that info will not be updated by 'make'.

Best regards,
Marcel Loose.