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Re: libsigsegv?

From: Eli Zaretskii
Subject: Re: libsigsegv?
Date: Thu, 11 Sep 2014 19:04:49 +0300

> Date: Thu, 11 Sep 2014 19:49:19 +0400
> From: Dmitry Antipov <address@hidden>
> CC: address@hidden
> On 09/11/2014 07:08 PM, Eli Zaretskii wrote:
> > Apropos stack overflow protection: why not use libsigsegv if it is
> > available?  It is capable of doing what we want (AFAICT), and supports
> > more platforms, including MS-Windows.
> 1. Stefan's mood gets worse after each new library dependency.

But what is your take on this?

Please note that my suggestion is to use the library only
_if_available_, and only for stack overflow detection.

> 2. Basically libsigsegv uses the following heuristics to distinguish between
>     stack overflow and other kinds of SIGSEGVs:
>     a) If the fault address is near the stack pointer, it's a stack overflow.
>     b) If the fault address is near and beyond the bottom of the stack's 
> virtual
>        memory area, it's a stack overflow.
>     c) If the stack pointer is near the bottom of the stack's virtual memory 
> area,
>        it's a stack overflow.
>     Currently we have only b), and this is the only thing which can be 
> implemented
>     staying in POSIX interfaces and without architecture-dependent tricks.

But libsigsegv already did all those tricks, and it stays stable for
quites some time on many platforms (the long and impressive list is in
the library, I suggest to take a look).  So why not use all that
knowledge and experience?

>     a) may be implemented in a small forest of #ifdefs, and it
>     doesn't worth using an extra library.

Are you going to implement it for the platforms we support?  The
library is exceedingly small and static, btw.

>     c) is the most controversial - for example, on GNU/Linux it works
>     by opening and reading /proc/self/maps.  Do you really want to open and 
> read file
>     on SIGSEGV?  I do not.

/proc/self/maps is not a real file, AFAIK.

Besides, other projects do that (e.g., Gawk).  I don't see why we

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