Re: xsrc/58872: libXfont and libXfont2 fixes with ssp [patch]

[Nat Sloss <nathanialsloss%yahoo.com.au@localhost>]

Hi,

If I printf (buffer) the value is valid. but it still crashes in atof


if i print the buffer and print the value for x and XLFD_NDIGITS all is well, 
and it works.

Thats why I think its due to to optimization settings applied to the file -O2 
instead of -O0.

Best regards,

Nat



On Wed, 4 Dec 2024 17:55:01 Martin Husemann via gnats wrote:
> The following reply was made to PR xsrc/58872; it has been noted by GNATS.
> 
> From: Martin Husemann <martin%duskware.de@localhost>
> To: gnats-bugs%netbsd.org@localhost
> Cc:
> Subject: Re: xsrc/58872: libXfont and libXfont2 fixes with ssp [patch]
> Date: Wed, 4 Dec 2024 07:51:52 +0100
> 
>  On Tue, Dec 03, 2024 at 11:20:02PM +0000, Nat Sloss via gnats wrote:
>  >  +	volatile double result;
>  >  
>  >   	char buffer[40];
>  >  
>  >  -	sprintf(buffer, "%.*lg", XLFD_NDIGITS, x);
>  >  -	return atof(buffer);
> 
>  How can a 40 char buffer be overrun with that format and XLFD_NDIGITS = 3?
> 
>  I would suggest to make the 40 depend on XLFD_NDIGITS, but that would be
>  an upstream change (and not affect things here).
> 
>  Please capture a value where this overrun happens, turn it into a test
> program and lets debug what goes wrong with your sprintf call.
> 
>  Martin