[64bit] emacs is unable to call subprocesses if display-time-mode is set

Corinna Vinschen corinna-cygwin@cygwin.com
Wed Apr 3 20:49:00 GMT 2013


On Apr  3 22:02, Corinna Vinschen wrote:
> On Apr  3 21:03, Corinna Vinschen wrote:
> > On Apr  3 14:00, Ken Brown wrote:
> > > On 4/3/2013 10:05 AM, Corinna Vinschen wrote:
> > > >I can reproduce the issue but it's tricky to debug.  The exception
> > > >occurs in the forked process and GDB can't follow fork on Cygwin.
> > > >
> > > >Btw., can you create an emacs which is built without optimization
> > > >and non-stripped this would simplify debuigging a bit...
> > > 
> > > It was already built without optimization.  I'm working on building
> > > a non-stripped version, but cygport isn't cooperating.  If you put
> > > "RESTRICT=strip" into the .cygport file, then cygport doesn't
> > > package the sources.  So you get a binary with debugging symbols,
> > > but you don't get the corresponding sources.
> > > 
> > > I'll send Yaakov a patch, but in the meantime I'm working around
> > > this. It shouldn't be long.
> > 
> > I'm still debugging this and something is very fishy when building
> > the environment for a process-to-exec.  I tracked it down to a
> > specific string duplication in Cygwin's build_env function which
> > seems to overwrite administrative data on the cygheap for some
> > reason I didn't quite follow yet.
> > 
> > This may take some time...
> 
> I found it.  When using the display-time-mode option, emacs opens and
> reads /proc/loadavg.  The problem was that the buffer allocated in
> format_proc_loadavg is too small, so the subsequent sprintf overwrites
> unrelated data on the cygheap.
> 
> In fact, this problem occurs on 32 bit as well, so I fixed it in CVS
> HEAD in the first place.  It's kind of a miracle that this has never
> been encountered in the 32 bit version before.  The problem exists
> since at least Cygwin 1.7.10.
> 
> I'm going to build a new 64 bit Cygwin right now, which I will upload
> in half an hour or so.  Please give it a try.

I just uploaded 1.7.18-16 to the 64 bit repo.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat



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