3.0.x HEAD crashing

[Phil Mayers]

Ok, now that backtrace and debugging are working again, back to top of 
thread for the issue.

Just had another crash on HEAD of 3.0.x; digging into the core file, it 
does look like malloc state has become corrupted - segfault is inside 
glibc with:

#5  _int_malloc (av=0x7f4ccc000020, bytes=<value optimized out>) at 
malloc.c:4476
4476	      bck->fd = unsorted_chunks(av);
(gdb) print bck
$1 = (struct malloc_chunk *) 0x0

Higher stack has:

#7  0x00000036ad40663f in __talloc (ctx=<value optimized out>, 
el_size=<value optimized out>, count=<value optimized out>, name=<value 
optimized out>) at ../talloc.c:560
560			tc = (struct talloc_chunk *)malloc(TC_HDR_SIZE+size);
(gdb) print size
$2 = 191

i.e. a perfectly ordinary malloc from talloc. Does everyone else agree 
this suggests heap corruption?

Full backtrace here:

https://gist.github.com/philmayers/18a04e642803153a4d5a

Will try and re-trigger under valgrind, though memcheck seems to report 
a *lot* for 3.0.x head - many alloc-without-free for regexp compilations 
at compile parse time and similar.