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Re: Compiling multiple sources in one command implicitly

From: EricDeb
Subject: Re: Compiling multiple sources in one command implicitly
Date: Wed, 20 Feb 2008 13:03:20 -0800 (PST)

OK, I see where you're going with the sentinel file. While still tedious, I
think it's workable. Thanks for the help!

Paul Smith-20 wrote:
> On Wed, 2008-02-20 at 11:55 -0800, EricDeb wrote:
>> Is there a feature in GNU Make that will let me compile several source
>> files with a single command implicitly? I understand I could write
>> rules like this:
>> a.o b.o c.o d.o : a.c b.c c.c d.c
>>      $(CC) -c $(CPPFLAGS) $?
> You definitely DON'T want to do this.  This does completely the wrong
> thing, and will fail badly if you ever try to run parallel builds (at
> least).
>> But, this causes a few problems. First, if any of the .o's are missing
>> we'll compile all four sources. Second it will be tedious to create
>> the makefiles like this, especially since this project has many many
>> files in it.
> Unfortunately GNU make doesn't have any ability to define multiple
> targets being built from a single invocation of a rule when creating
> explicit rules like this.
> Even if it did, what you want is slightly different because that
> behavior would assume that ALL the targets would be built from a single
> invocation.
> The only way you can do this is with a sentinel file, like this:
>         .sentinel: a.c b.c c.c d.c
>               $(CC) -c $(CFLAGS) $(CPPFLAGS) $?
>               @touch $@
>         a.o b.o c.o d.o: .sentinel
> Unfortunately there are still holes in this: for example if someone
> deletes a .o file then this won't rebuild anything; you'd have to
> explicitly delete the .sentinel file by hand.
> There may be ways to work around this as well, but it would require some
> fancier footwork.
> -- 
> -----------------------------------------------------------------------------
>  Paul D. Smith <address@hidden>                
>  "Please remain calm--I may be mad, but I am a professional."--Mad
> Scientist
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