Fw: Problems with compiling autogen with GCC8 or newer versions

[Bruce Korb]

Hi,

On 1/10/21 3:56 PM, Martin Sebor wrote:
> Sure.  I was confirming that based on the GCC dump there is no risk
> of an overflow in the translation unit, and so there is no warning.

OK. :) I didn't understand the GCC dump. Despite having commit privs, 
I'm not actually a compiler guru.

>> It can /not/ overflow. Those compiler stats are not decipherable by me.
>
> They indicate the minimum, likely, maximum, and unlikely maximum
> number of bytes of output for each directive and the running totals
> for the call (in parentheses).  The relevant lines are these:
>
>   Directive 2 at offset 2: "%s"
>     Result: 0, 255, 255, 255 (2, 257, 257, 257)
>
> The result tells us that the length of the %s argument is between
> 0 and 255 bytes long.
It should be 1 to 255. 0 is actually impossible, but it would take crazy 
complicated sleuthing to figure it out, even though the "spn_*" 
functions should be inlined.
>
> Since objsize (the size of the destination) is 520 there is no
> buffer overflow.
The size of the destination is guaranteed to be between 263 and 518 
bytes. The "def_str" pointer will always point at least two bytes past 
the start of the 520 byte buffer.
>
> The note in the forwarded message indicates that GCC computes
> the destination size to be much smaller for some reason:
>
>   note: 'sprintf' output between 4 and 259 bytes into a destination of 
> size 255
>
> I.e., it thinks it's just 255 bytes.  As I explained, such a small
> size would trigger the warning by design.
Yep. If it can accurately figure out the minimum size remaining, that 
would be completely fine. "If."
>   I can't really think of
> a reason why GCC would compute a smaller size here (it looks far
> from trivial).
If it can figure out that the minimum size is 263, that'd be great. If 
it can't, it needs to be quiet.
>   We'd need to see the original poster's translation
> unit and know the host and the target GCC was configured for.

OK. Not anything I can do. Thomas would have to send in his version of 
"gd.i".


Thank you!

Regards, Bruce