Re: non recursive makefiles

[Pascal J . Bourguignon]

Adrian Robert writes:
> >> IMHO precompiled headers support is much more important as the
> >> compilation speed-up is enormous (day to day experience on Mac OS X
> >> using Xcode).
> >
> > ...
> > The ROI (Return On Investment) of working on precompiled headers would 
> > be
> > huge compared to other changes we might develop.
> 
> Doesn't the compiler still have to parse in the precomp headers so it 
> can use the structure information there to help parse the rest of the 
> code?  (I guess everyone thinks this is much faster than the original 
> .h file reading / parsing, but the stated lack of numbers backing it up 
> prompts a devil's advocate question.)

Of course.  Unless you dump a mmap-able data structure.  Which means
you'd replace all pointers with indexes, therefore making every read
access theorically slower (in practice, it may be in cache and not
matter since the I/O is where time will be spent anyway). So the
question is whether the precompiled header are smallers and tighter
than the original ASCII files.  Perhaps doing: 

     ar c precomp.h /usr/include/*.h

is all that would be needed.


> Also, note speedup in Xcode vs. PB is due to more than just PCH:
> 
> - switch to 'jam' instead of 'make'
> - extensive use of incremental compilation in background
> - zero-link (whatever that is)
> - if you are using it, distributed compile


-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
You never feed me.
Perhaps I'll sleep on your face.
That will sure show you.