Re: Using -MMD instead of -MD for depndency generation

[Ralf Wildenhues]

Hello Holger,

thanks for the report.

* Holger Freyther wrote on Sat, Oct 23, 2010 at 10:47:47PM CEST:
> when typing make in the build directory of WebKit/GTK+ it takes multiple
> minutes until the first file is compiled.

Can you go into (a lot) more detail here?  What happens during those
minutes, which processes are running (look at ps output etc.)?  Is this
cold-cache or hot-cache?  Only the first time the code is compiled, or
the build tree is used, i.e., does it happen again after 'make clean'?
Or are you talking about configure (-q?) run time here?

What system is this on, is it very loaded with other processes?
Can you please post a link to the tarball you're compiling from, so we
can try to reproduce this?

> I would like to reduce the size of the
> .Plo (dep files) in my build tree and build them with -MMD instead of -MD. Is
> there a way to instruct automake to use -MMD for gcc3 like depmode?

No, there isn't, but also, in my experience, that will not help all that
much at all.  All files listed as dependencies with -MD will be opened
anyway by the compiler eventually, and a list of files usually won't
amount to sizeable file size.

I'm still guessing that it's something else that slows down your build
by so much.

Thanks,
Ralf