Re: Any way to get rid of -MP parameter to gcc for dependency creation?

[Ralf Wildenhues]

* Xan Lopez wrote on Tue, Jan 04, 2011 at 02:21:01PM CET:
> The system is Fedora 13
> with ext4, kernel 2.6.34, CPU i7 2.67Ghz and the HDD is a standard
> laptop 7200rpm thingie.
> 
> Without the local hack to get rid of the -MP flag a null-build with
> that version of GNU make is ~40s. CVS HEAD gives ~26s (wow!), and CVS
> HEAD with the "get rid of -MP" hack gives ~14s. So definitely there's
> been a big improvement in Make in the last year, thanks for pointing
> that out. It still seems worth to try to improve the -MP case though,
> 26 > 14 is a big win.

> > Then, how many stub targets get added due to -MP in your project?
> 
> Some grep hackery gives me 3,030,859 empty rules in total in all .Plo
> files in the build tree.

> > FWIW, on big systems I typically just put the build tree on a ramdisk

> I've tried this and there's basically no perceptible difference
> AFAICT. I only have the builddir in /dev/shm, since I don't think I
> can fit the whole thing in RAM in my laptop. Hope it helps.

Thanks for the data.  This is a bug in GNU make.  I'm working on a fix.

Cheers,
Ralf