On 2006-01-15 21:04, Jason Evans <[EMAIL PROTECTED]> wrote: > On Jan 14, 2006, at 1:32 PM, Giorgos Keramidas wrote: > >On 2006-01-13 11:07, Jason Evans <[EMAIL PROTECTED]> wrote: > >>On Jan 12, 2006, at 5:29 PM, Giorgos Keramidas wrote: > >>> > >>>[...] > >>> > >>>Does this look like an off-by-one error to you too Jason? > >>>Apparently, the allocated size of s->data is s->size, which is 873 > >>>bytes, but then Emacs tries to access s->data[873]. > >>> > >>>Does it look like I'm right in thinking that this is a bug in Emacs? > >> > >>This looks like a bug in emacs, as you say, but I don't know if it > >>has any particular relation to the posix_memalign() changes. > > > >Apparently it does seem related to posix_memalign() changes. > >When I bootstrap Emacs without posix_memalign(), by manually > >tweaking src/config.h after configure runs, and #undef > >POSIX_MEMALIGN, then it passes the bootstrap stage normally. > > I looked into this some, and it appears that it is a configuration > problem in emacs. When I ran 'configure', both GNU_MALLOC and > HAVE_POSIX_MEMALIGN were defined in config.h. This appears to be a > recipe for disaster, since the allocator included with emacs does not > provide posix_memalign(). This probably means that emacs is calling > into both its own allocator and libc's, then trying to free memory > that was allocated by libc, using its own allocator. > > Additionally, I see dlmalloc-specific code that tells dlmalloc not to > mmap() during allocation, since emacs's undump procedure doesn't > preserve mmap'ed regions. > > It looks like emacs is by default configured to use emacs's > allocator, which is good (getting emacs to work with FreeBSD's malloc > probably isn't worth the trouble). However, the emacs code makes the > mistake of deciding whether to use posix_memalign() based on > HAVE_POSIX_MEMALIGN, rather than something like USE_MEMALIGN -- emacs > is mixing and matching allocators and their features, which is not > good. I'm not familiar enough with emacs's configuration system to > know the correct way of fixing this, but one way or another, emacs > needs to not use posix_memalign().
Jason, thanks for the time you spent into this :) If disabling posix_memalign() fixes the problems of Emacs's use of allocators, I'll probably submit a patch to emacs-devel to do exactly this. It's one of the things RMS himself wouldn't object to, as he has stated already, so I think it's fine for the time being. _______________________________________________ cvs-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/cvs-all To unsubscribe, send any mail to "[EMAIL PROTECTED]"
