Re: revision control info in generated files

[Jef Driesen]

On 30/03/10 20:57, Ralf Wildenhues wrote:
> * Jef Driesen wrote on Wed, Mar 17, 2010 at 01:23:09PM CET:
> > On 16/03/2010 14:22, Peter Johansson wrote:
> > > Which method to use depends on where you want the MY_REVISION_VERSION to
> > > propagate. Do you need it in any Makefiles, e.g., or do you only need it
> > > compiled into your program.
> >
> > I only need it compiled into my library. The goal is that an
> > application using my library can report the exact revision of the
> > library (for diagnostic purpose).
> >
> > With the solution I outlined in my previous posts, I can already get
> > the "normal" version info (e.g. the major.minor.micro numbers) into
> > a public header file to allow for compile time version checking.
> > Runtime version checking can easily be achieved by adding a
> > mylib_get_version() function to the library. But when building not
> > yet released code, it's more useful to know the exact SCM revision,
> > rather than the version numbers.
>
> FWIW, below is what I use in my own projects.  I use git exclusively as
> SCM, and I am fine with VERSION being stable for a long time, and I
> don't care about finer version information in configure.
>
> There is a point to using FORCE over .PHONY: were you to mark
> $(srcdir)/.git-version as phony, then the compilation of version.c would
> always be emitted by 'make', even if the .git-version fils is up to
> date.

Is FORCE some special built-in name (like .PHONY)? Or is just a random 
name for an "empty" target (e.g. one that depends on nothing and does 
nothing).

> Hope that helps.  I'm sure you can easily adapt this to the SCM of your
> choice.

Sure. I use both git and subversion, and this are the commands I would 
use to retrieve the revision info:

git rev-parse --quiet --verify HEAD
svnversion

The svnversion command is a little tricky because it does not fail when 
run outside a subversion tree.

> FORCE:
> $(srcdir)/.git-version: FORCE
>         @if (test -d $(top_srcdir)/.git&&  cd $(srcdir) \
>         &&  { git describe --dirty || git describe; } )>  .git-version-t 
> 2>/dev/null \
>         &&  ! diff .git-version-t $@>/dev/null 2>&1; then \
>           mv -f .git-version-t $@; \
>         else \
>           rm -f .git-version-t; \
>           if test -f $@; then :; else touch $@; fi; \
>         fi
>
> EXTRA_DIST = $(srcdir)/.git-version
> CLEANFILES = .git-version-t
>
> version.c: $(srcdir)/.git-version Makefile.am
>         echo "const char foo_version[] = \""`cat $(srcdir)/.git-version`"\";">  
> $@
>
> foo_SOURCES += version.c

I think I understand what's going on, except for a few little things:

Why the depencency on Makefile.am? I assume it has something to do with 
that FORCE target?

Why do you add the .git-version-t file to CLEANFILES if it gets removed 
in the script?

And last but not least I'm using VPATH builds to build my code for 
multiple platforms from the same source directory. Shouldn't the 
.git-version file be created inside the build directory, rather than the 
source directory?