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Re: [PATCH] Support for GNU make dependency generation
From: |
David M. Warme |
Subject: |
Re: [PATCH] Support for GNU make dependency generation |
Date: |
Tue, 26 Oct 2010 10:19:01 -0400 |
Automake handles only simple cases.
Consider automatically generated include files, or an m4 script
that sinclude's the generated dependency file. I am reluctant
to design features that handle only simple cases.
The execution time of m4 scripts has never been a serious factor
in my experience.
This still leaves problem #1 wide open.
On Tue, 2010-10-26 at 07:56 -0600, Eric Blake wrote:
> On 10/26/2010 07:41 AM, David M. Warme wrote:
> > 2. By creating both the dependency file and the actual m4 target
> > file in one step, you wind up being in danger of "circular
> > dependencies" -- running make twice in a row causes stuff to
> > be remade the second time. In certain cases, even an endless
> > succession of "make" invocations causes stuff to get remade
> > every time. Single commands that update two or more targets
> > at once are the usual cause of this behavior. The fix is to
> > have two separate rules in your Makefile:
>
> I'm reluctant to have to require to run m4 twice per file. Dependencies
> as a side effect of compilation is the most efficient way to generate
> dependencies, and running twice defeats this. There's a reason that
> automake prefers to generate dependencies during compilation, and if
> automake can write portable makefiles with gcc dependencies generated
> during compilation, then I see no reason why m4 can't be hooked up to do
> the same.
>