[Ffmpeg-devel] swscale.c compile error[PATCH]

[Måns Rullgård]

Diego Biurrun <diego at biurrun.de> writes:

> On Sun, Nov 05, 2006 at 02:10:49PM +0000, M?ns Rullg?rd wrote:
>> Diego Biurrun <diego at biurrun.de> writes:
>> 
>> > On Thu, Nov 02, 2006 at 05:33:48PM +0100, Michel Bardiaux wrote:
>> >> Ismail Donmez wrote:
>> >> >02 Kas 2006 Per 17:37 tarihinde, Michel Bardiaux ?unlar? yazm??t?: 
>> >> >>I think there's a bug in the Makefile, version.h is not re-made after an
>> >> >>update. A possible fix is to change the line in the top Makefile to:
>> >> >>
>> >> >>version.h: .svn/entries
>> >> >
>> >> >This is more clean imho.
>> >> 
>> >> Also, I have just realized that with .PHONY, a full recompile of all in 
>> >> the top directory (ffmpeg.c,etc) occurs at every make. While with the 
>> >> dependency to .svn/entries, rebuild occurs only if there is a real 
>> >> change to the svn version number. Ecco.
>> >
>> > This rebuild puzzles me.  version.h is not changing...
>> 
>> No, but the .PHONY makes make pretend that it did.
>
> No, .PHONY makes the target get run unconditionally.  But version.sh
> checks if version.h is changed and only recreates it if there was a
> change ...

.PHONY does more than that.  Quoting info manual:

   A phony target should not be a prerequisite of a real target file;
   if it is, its commands are run every time `make' goes to update
   that file.  As long as a phony target is never a prerequisite of a
   real target, the phony target commands will be executed only when
   the phony target is a specified goal (*note Arguments to Specify
   the Goals: Goals.).

-- 
M?ns Rullg?rd
mru at inprovide.com