Re: stack bounds

[Paul Eggert]

On 10/10/20 2:49 PM, Bruno Haible wrote:
> gcc -fstack-clash-protection -m32 -O2 stackish.c fixes this issue.

Yes. However, the GCC manual says this about -fstack-clash-protection:

     Most targets do not fully support stack clash protection.  However,
     on those targets '-fstack-clash-protection' will protect dynamic
     stack allocations.  '-fstack-clash-protection' may also provide
     limited protection for static stack allocations if the target
     supports '-fstack-check=specific'.

which is not as close to "it should just work" as I'd like, especially when I go 
read the section on -fstack-check. I suppose I need to look at the output of gcc 
-S -fstack-clash-protection on my platform (and understand what the OS does) to 
know whether stack overflow is detected reliably.

That being said, it does look like a reliability win if we start using 
-fstack-clash-protection on platforms like Fedora x86-64 that support it and do 
not enable it by default. Perhaps we should have a Gnulib or Autoconf macro that 
does that.