bug#23726: emacs 25.0.94 crashes

[Paul Eggert <eggert@cs.ucla.edu>]

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Has Rawhide incorporated some of Florian Weimer's malloc patches? If so, 
this is almost surely causing the problem. I will CC: Florian to give 
him a heads-up. See:

https://sourceware.org/ml/libc-alpha/2016-06/msg00211.html

https://sourceware.org/bugzilla/show_bug.cgi?id=19564

I am surprised that you can use valgrind. Valgrind does not work on 
Emacs in Fedora 23 because it mishandles the way Emacs dumps and 
restores. I can use Valgrind only on temacs, not on Emacs itself. The 
fact that you can use Valgrind on a dumped Emacs suggests that some of 
the malloc patches have been installed on Rawhide.


For what it's worth, when I try to use valgrind on Fedora 23, I run into 
what appears to be a valgrind bug that prevents Emacs from working. I 
just now filed it here:

https://bugzilla.redhat.com/show_bug.cgi?id=1344082

I ran valgrind as follows:

valgrind --log-fd=3 --suppressions=valgrind.supp ./temacs 3>/tmp/vg.log

with the attached valgrind.supp file, and Emacs (emacs-25 branch, built 
with 'configure --with-x=no') says "Failed select: Bad address" due to 
the valgrind bug. How do you use valgrind on Rawhide?


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# valgrind suppression file
# Usage:
#    valgrind --suppressions=valgrind.supp ./temacs

# Conservative garbage collection inherently looks at uninitialized values,
# and Fgarbage_collect and its callees all depend on this.
# It's hard to separate out exactly which callees need to be listed here,
# since the C compiler can inline them.  Also, valgrind doesn't care
# about the use of uninitialized variables directly, only when their values
# are eventually used.  So just list Fgarbage_collect and its callees.
{
   Fgarbage_collect Cond - conservative garbage collection
   Memcheck:Cond
   ...
   fun:Fgarbage_collect
}
{
   Fgarbage_collect Value8 - conservative garbage collection
   Memcheck:Value8
   ...
   fun:Fgarbage_collect
}
# valgrind only looks at the last few callees on the stack, but
# mark_object can call itself recursively and deeply.  So list
# it too, in case Fgarbage_collect is a long way from the stack top.
{
   Fgarbage_collect Cond - conservative garbage collection
   Memcheck:Cond
   ...
   fun:mark_object
}
{
   Fgarbage_collect Value8 - conservative garbage collection
   Memcheck:Value8
   ...
   fun:mark_object
}

# On one circa-2011 x86-64 GNU/Linux platform, strlen is inlined to
# something that loads 4 bytes at a time.
{
   init_buffer optimized strlen
   Memcheck:Addr4
   fun:init_buffer
}