Re: revision control info in generated files

[Jef Driesen]

On 02/04/10 14:37, Peter Johansson wrote:
> On 4/2/10 7:04 AM, Jef Driesen wrote:
> > The problem I'm trying to solve is that I already have a version.h
> > that is generated from a version.h.in template that contains:
> >
> > #define MYLIB_VERSION_MAJOR @MYLIB_VERSION_MAJOR@
> > #define MYLIB_VERSION_MINOR @MYLIB_VERSION_MINOR@
> > #define MYLIB_VERSION_MICRO @MYLIB_VERSION_MICRO@
>
> I would extend version.h.in to also have a line
>
> #define MYLIB_SVN_REVISION @MYLIB_SVN_REVISION@
>
> and use sed to generate version.h from version.h.in where you replace
> @MYLIB_VERSION@ with values you already have AC_SUBSTed into Makefile
> and MYLIB_SVN_REVISION is replaced with content of
> $(top_srcdir)/.svn_revision. It might help to look at how Autoconf
> creates autoheader et al. from *.in files using edit.
>
> http://www.gnu.org/software/autoconf/manual/autoconf.html#Installation-Directory-Variables

I now have

version.h: $(srcdir)/version Makefile.am
   $(AM_V_GEN) sed \
      -e 's/address@hidden@/@MYLIB_VERSION_MAJOR@/' \
      -e 's/address@hidden@/@MYLIB_VERSION_MINOR@/' \
      -e 's/address@hidden@/@MYLIB_VERSION_MICRO@/' \
      -e 's/address@hidden@/'`cat $(srcdir)/version`'/' \
      $(srcdir)/version.h.in > $@

mylib_la_SOURCES += version.c
mylib_HEADERS += version.h

BUILT_SOURCES = version.h
EXTRA_DIST += $(srcdir)/version
CLEANFILES += version-t

Took me a while to figure out the escaping of the @ symbol. It seems to 
work fine, except that I would like to add "$(srcdir)/version.h.in" as a 
dependency for "version.h". But when I add that, make distcheck fails 
and I don't know why.

The error I get is:

make[3]: *** No rule to make target `../../src/version.h.in', needed by 
`version.h'.  Stop.

> > I also have a corresponding version.c file that has the same info, but
> > for use at runtime:
> >
> > #include "version.h
> > const int mylib_version_major = MYLIB_VERSION_MAJOR;
> > const int mylib_version_minor = MYLIB_VERSION_MINOR;
> > const int mylib_version_micro = MYLIB_VERSION_MICRO;
>
> This should not be a problem when you have the generated version.h. You
> can just use the defines from version.h. The tricky thing is that
> version.cc will not compile if version.h is not present (not generated
> yet), so you need to have a dependency that version.h needs to be
> generated before version.o is created.
> Read the section 9.4 in Automake manual that explains the details clearly
>
> http://sources.redhat.com/automake/automake.html#Sources

The line

BUILT_SOURCES = version.h

should take care of that, not?

> > (Or with functions to avoid the problem of exporting variables from
> > Windows DLL, but that's not relevant here.)
> >
> > It would be nice if I could get the revision info into the same file,
> > so related stuff is not spread over different files. No big deal if
> > that is not possible, but I also have other files where I could use
> > the revision info. For instance on windows I have a resource file
> > (*.rc) with version info. I can probably solve that by generating a
> > short version-revision.h file and include that.
>
> It is a good idea to store the revision in a separate file, e.g.,
> $(top_srcdir)/.svn_revision
>
> It makes it easy to parse out that info and propagate to other places,
> and if you use the rule described by Ralf the time-stamp of this file
> will only change when the content needs to be changed, so you can have
> files depending on that time-stamp.

I now have a slightly modified version of Ralf' rule:

FORCE:
$(srcdir)/version: FORCE
   @if (test -d $(top_srcdir)/.git && cd $(srcdir) \
        && git rev-parse --verify HEAD ) > version-t 2>/dev/null \
     && ! cmp -s version-t $@; then \
     mv -f version-t $@; \
   else \
     rm -f version-t; \
     if ! test -f $@; then touch $@; fi; \
   fi