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Message-Id: <200005111720.MAA19448@hp2.xraylith.wisc.edu>
To: DJ Delorie <dj AT delorie DOT com>
cc: tprince AT computer DOT org, abegel AT cs DOT berkeley DOT edu, cygwin AT sourceware DOT cygnus DOT com
Subject: GCC snapshots and mmap problem [Re: GDB hangs on Win2K]
In-reply-to: Your message of "Thu, 11 May 2000 13:10:15 EDT."
             <200005111710 DOT NAA24928 AT envy DOT delorie DOT com> 
Date: Thu, 11 May 2000 12:20:11 -0500
From: Mumit Khan <khan AT NanoTech DOT Wisc DOT EDU>

DJ Delorie <dj AT delorie DOT com> writes:
> 
> > There seems to be a problem in mmap I've trying to find for days
> > now with no luck. Essentially, ./stage1/xgcc is hanging when
> > garbage collecting (compiling fold-const.c), and the only solution
> > for now is to configure with --with-gc=simple which works but
> > really slows down compilation.
> 
> Saw that myself, except mine crashed all the time instead of hanging.
> It might be the new /dev/zero code, too.

GCC is using MAP_ANON, so /dev/zero shouldn't affect it, unless I'm
missing something. 

> Note that the djgpp crew has already submitted patches to speed up
> ggc-simple.c and/or allow more widespread use of ggc-page (all I know
> is that they solved the "problem" for djgpp).

I've been following that with great interest, since that'll help Mingw
as well (however, it's pretty trivial to write mmap for Mingw, but I 
just haven't included that yet in libiberty yet). Of course, since 
Cygwin already supports mmap, we need to figure out where the problem 
is. I'm going to use a debuggable Cygwin DLL and see if I get anywhere.

Can someone check if the problem goes away with thread-disabled Cygwin
DLL? Note that in my case it's hanging in munmap (unless it's also
popping up a window on the local box, which I can't see when logged on
remotely, sigh), which may point to a Cygwin waiting on a lock. Cygwin
currently uses a single resource lock, even though the basic framework 
for using multiple locks is there via LOCK_ macros, so a single mismatched
Set/Release lock may cause problems. I can't check currently since I'm 
connecting to my home net via modem, and don't have gcc on my laptop.

Regards,
Mumit


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