Re: Generating sources

[Roger Leigh]

Alexandre Duret-Lutz <address@hidden> writes:

Hi Alexandre!

> Roger Leigh wrote:
> | In a project, I am preprocessing the C++ source and headers.  That is:
> | foo.ccg -> foo.cc
> | foo.hg -> foo.h
> |
> | Some custom m4 I wrote processes the files with some simple rules:
> |
> | $(top_builddir)/build/classgen.m4f: $(top_srcdir)/build/classgen.m4
> |         $(M4) -P -F $@ $^
>
> $^ is not portable.
>
> Please forgive me if you are assuming GNU Make, but as Automake
> strives to produce portable Makefiles and many people
> unconsciously break this portability when writing custom rules,
> I don't want someone who read the archives to blindingly copy
> the above...

No problem.  In this case I've made GNU make as a requirement, since I
have no means to do portability testing with non-GNU makes, so I don't
have to worry about portability.  However, some of your suggested
alternatives are much more concise, so I'll doubtless convert to using
them.

> | libfoo_la_post_sources = \
> |         $(addsuffix .cc,$(basename $(filter 
> %.ccg,$(libfoo_la_pre_sources)))) \
> |         $(addsuffix .h,$(basename $(filter %.hg,$(libfoo_la_pre_sources))))
>
> In POSIX words:
>
>   libfoo_la_post_sources = $(libfoo_la_pre_sources:g=)

Yes :-)  I think this is a lot easier to understand!!

> | libfoo_la_SOURCES = \
> |         $(libfoo_la_pre_sources) \
> |         $(libfoo_la_post_sources) \
> |         bar.cc \
> |         bar.h \
> |
> | If I touch foo.ccg, foo.cc is regenerated and foo.lo rebuilt.
> | However, if I touch foo.hg, foo.h is not rebuilt, which is causing
> | problems (I need to do a manual "make foo.h" every time I alter
> | foo.hg).
>
> One issue with this setup is that foo.h doesn't exist the first
> time you try to compile the *.cc files that include it, and as
> dependency information is not available yet make won't help.
> Hence you have type `make foo.h'.  On the following runs,
> however, dependency information is there, so I'd expect foo.h to
> be rebuilt before anything that depends on it is compiled.
>
> It doesn't exactly correspond to you description, so maybe I'm
> missing something.

This is exactly my problem.

> The `Built sources' section of the manual discusses the above
> problem at lengths, and offer several solutions.  The more
> common is to use BUILT_SOURCES.

Thanks.  I've made the changes you suggested, and it did the trick.
BUILT_SOURCES triggers the source generation prior to the actual
compile.

The POSIX inference rules look very handy too, but I've not had a
chance to test them yet.


Many thanks,
Roger

-- 
Roger Leigh

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