GNU OSC (Object Size Checking)

[Yuchen Zhou (yuczhou)]

Thank you Martin, Jonathan. I think I understand it now. Of cause I may have further questions in the future.
 
By the way, is the -O2 option a must for OSC? What about other optimization levels? I did not find much details on it. 

Thanks!

Yuchen Zhou
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-----Original Message-----
From: Jonathan Wakely [mailto:jwakely.gcc@gmail.com] 
Sent: Tuesday, February 6, 2018 1:43 PM
To: Martin Sebor <msebor@gmail.com>
Cc: Yuchen Zhou (yuczhou) <yuczhou@cisco.com>; gcc-help@gcc.gnu.org
Subject: Re: GNU OSC (Object Size Checking)

On 6 February 2018 at 20:19, Martin Sebor wrote:
> But no runtime protection happens for libstdc++ containers, even with 
> _FORTIFY_SOURCE, because libstdc++ either uses the GCC built-in 
> functions (__builtin_memcpy) directly or "rolls" its own loops 
> (std::copy, etc.) that GCC transforms into calls to the non-checking 
> built-ins.  For the former, it might be worth considering using the 
> checking built-ins instead.  Jonathan will know best if this would 
> make sense and how much it might benefit.  For the latter, I'm sure 
> there are opportunities for GCC to do better and check the bounds of 
> the copies either before emitting calls to these functions or 
> propagating their bounds.

My completely unsubstantiated guess is that people might pass out-of-bounds pointers to std::string members more often than other containers.

We certainly could add more checking, but I don't know if it's worth prioritizing. There are thousands of things we could do with more hands to do the work.

I've opened https://gcc.gnu.org/PR84256 so it isn't forgotten.