[CMake] dependency hell with custom commands and multiple outputs

[Romain CHANU]

Hi Michael.

I got the same situation here. I am using a command which outputs a lot of
files (>100 files).

Have you tried what David is suggesting?

Thank you to update us.

Cheers,

2010/1/13 Michael Wild <themiwi at gmail.com>

> Hmmm, thought of something like that myself, but am not sure whether
> dependencies will be handled correctly. Of course, I'll have to label the
> products as GENERATED and add them to  ADDITIONAL_MAKE_CLEAN_FILES. Will
> give it a try...
>
>
> Michael
>
>
> On 13. Jan, 2010, at 16:17 , David Cole wrote:
>
> > The best way to deal with this is probably to have a single "sentinel" or
> > "stamp" file that gets generated *every* time the command runs. And then
> > list that file as it's only output that CMake knows about... (But still
> with
> > the full list of inputs.)
> >
> > Does that work?
> >
> >
> > On Wed, Jan 13, 2010 at 8:26 AM, Michael Wild <themiwi at gmail.com> wrote:
> >
> >> Hi all
> >>
> >> I just ran into an interesting problem. Say I have a custom command that
> >> produces several files, but only updates them as needed. E.g.
> >>
> >> add_custom_command(OUTPUT file1.c file2.c file3.c
> >> COMMAND generator file1.inp file2.inp file3.inp
> >> DEPENDS generator file1.inp file2.inp file3.inp
> >> VERBATIM)
> >>
> >> Now, suppose that file2.inp is changed, the build system will run the
> >> command to update the output. Now, the "generator" program is really
> smart
> >> and only updates file2.c. This causes all hell to break lose (at least
> with
> >> the GNU Makefile generator on OS X), causing the command to run three
> times,
> >> desperately trying to update file1.c and file3.c (because file2.inp is
> newer
> >> than them) and then, as it seems, gives up. The thing repeats with every
> >> invocation of "make".
> >>
> >> Now, the "generator" requires all the input files to be processed in one
> >> step, so I can't split the command as one would usually do. Also,
> touching
> >> all the output files after calling "generator" isn't really viable since
> I'd
> >> like to prevent unnecessary re-compilation of the produced .c files.
> >>
> >>
> >> Are there any good solutions to this problem?
> >>
> >>
> >> Michael
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