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Date: Tue, 25 Dec 2001 18:18:03 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
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In-reply-to: <k5gc2ukf47ujjbubu40f6u4eeofav85ku9@4ax.com> (message from Jason
	Green on Sun, 23 Dec 2001 20:42:48 +0000)
Subject: Re: Should I use bash as default shell in makefiles?
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> From: Jason Green <news AT jgreen4 DOT fsnet DOT co DOT uk>
> Newsgroups: comp.os.msdos.djgpp
> Date: Sun, 23 Dec 2001 20:42:48 +0000
> 
> I've just noticed the above command is slightly different to the one I
> see here, so I can't be sure we're looking at the same docs.  However, I
> believe you are refering to...
> 
> >    The purpose of the `sed' command is to translate (for example):
> > 
> >      main.o : main.c defs.h
> > 
> > into:
> > 
> >      main.o main.d : main.c defs.h
> > 
> > This makes each `.d' file depend on all the source and header files
> > that the corresponding `.o' file depends on.  `make' then knows it must
> > regenerate the prerequisites whenever any of the source or header files
> > changes.

Yes, that's what I had in mind.

> ...but when using `-MMD' the `.d' file will still be regenerated whenever
> any of the source or header files changes.

No, it's a chicken-and-egg problem: what happens if the .d file does
not yet exist?  Without main.d being mentioned in dependencies, Make
will not bother building it.

Also, I think some of the compilers don't have -MMD.  GNU Make is
supposed to work with compilers other than GCC ;-)