NetBSD-Users archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: [Q] emacs on 6.1 candidate (i386)

Greg Troxel <> wrote:

> * I'd say it's a bug in emacs if emacs crashes rather than prints a
>   message about stack size.

It's a bit of a pain to do it, so most programs don't bother.  When a
program exceeds its stack limit it gets a SIGSEGV for the stack
address at some random point.  It may happen when stack frame is
created and the registers you save spill over to the page that is over
the limit.  Or it may happen later in the function when you access a
local variable that is in the part of the stack that is over the
limit.  You need to have a SIGSEGV handler with an alternative stack
(or you would incur recursive SIGSEGV), examine the fault address,
examine the mcontext and determine that the fault address is a stack
address.  You need to know if your stack grows up or down.  If you
have a really big frame, the fault address may not be on the page
adjacent to the page where the stack pointer is.  Etc, etc, etc.  So
most programs just dump core at the offending instruction and you can
at least easily figure out what happened.


Home | Main Index | Thread Index | Old Index