[FFmpeg-devel] [PATCH] Speedup make removing implicit rules for makefiles and dependencies (cure for slow "make" in MSYS+MinGW)

[Måns Rullgård]

Adam Strzelecki <ono at java.pl> writes:

> @Reimar:
>
>> I assume Ramiro tested with MinGW and his numbers seem to contradict
>> your conclusions.
>> Are you sure you don't just have a broken make version?
>
> Okay I think I know where's the problem. I got "make clean" but not
> "make distclean" sandbox, so all .d dependency files are still there.
> Without .d files indeed it runs quick (for a first time). You got a
> point. The problem raises when .d files are already there, NOT when
> they do not exists (as I supposed initially) and this is the moment
> you do "make" after "make clean" or alternatively "make install" after
> "make". In both cases you gonna wait good while until something
> actually happens. (Please check that).

That is what I checked.  It takes about 1 second for make to figure
out nothing needs to be done.

> I have absolutely no idea why GNU Make tries to regenerate/build(?)
> using built-in implicit rules each Makefile it parses (or includes)...
> which in case of FFmpeg those are Makefile, common.mak, subdir.mak,
> config.mak and all .d files. Do you have any?

The GNU make manual talks about this.

-- 
M?ns Rullg?rd
mans at mansr.com