Re: [patch #6569] Allow grep to work in small stack environment

[Eric Blake]

On 08/27/2010 01:01 PM, Paul Eggert wrote:
> On 08/27/2010 01:39 AM, Jim Meyering wrote:
>
> >    - use xnmalloc, not malloc+test+return, so we don't ignore malloc failure.
> >    - use sizeof *VAR, not "sizeof TYPE" -- the former is more maintainable.
> >    - adjust indentation to retain declaration alignment
>
> There are many places in other GNU apps, including gnulib, where
> it's assumed that one can declare a 4 kB-or-so array on the stack without
> any problem.  So I'm surprised to see the need for this change to GNU grep.
> Surely we don't need to go through GNU apps and rejigger things for
> configurations with 4 kB stacks?  By today's standards, such stacks are
> ridiculously small.

4k in a non-recursive algorithm is probably fine for a non-threaded app; 
but if there is any chance for recursion, then stack-allocating a 4k 
array risks interfering with stack overflow detection, since that is 
larger than the guard page installed at the end of some stacks.  For 
threaded applications (and therefore libraries), it is much more common 
to have extremely limited stacks for each thread.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org