Re: [PATCH] Support for GNU make dependency generation

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.

-- 
Eric Blake   [email protected]    +1-801-349-2682
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