Thanks for reporting the bug. Please try the attached patch, which I 
installed into Gnulib.

stackvma.c says it contains simplified copies of code in vma-iter.c, 
which didn't have this bug. Bruno, am I right in guessing that there are 
two files mainly because libsigsegv was separate from Gnulib? Should we 
be working to unify the two files, so that fixes to one also fix the other?