Re: cc1plus: note: source object is likely at address zero

On Thu, 5 Mar 2026 at 13:43, Jonathan Grant <[email protected]> wrote:
>
>
>
> On 05/03/2026 13:31, Arsen Arsenović wrote:
> > Jonny Grant <[email protected]> writes:
> >
> >> Is there a way to make these "notes" appear as warnings? That can then
> >> be upgraded to errors by -Werror
> >> [...]
> >> <source>: In function 'int main()':
> >> <source>:18:11: warning: 'int __builtin_puts(const char*)' reading 1 or more bytes from a region of size 0 [-Wstringop-overread]
> >
> > ^ That part is the actual warning, so you want
> > -Werror=stringop-overread.
> >
> > The note is just added context for the warning (as per the usual - notes
> > serve to specify more info about diagnostics).
>
> Hello Arsen, Andrew
>
> Many thanks for pointing out it's the -Wstringop-overread that causes the warning.
> Maybe "from a region of size 0" is a little unclear, perahps it could be "from a region starting at address 0x0 (NULL)" Would that be a useful PR to raise?

I don't think so. The warning is far more general, it says "you're
reading N1 bytes from a region of N2 bytes", and in this specific case
it happens to be N2 == 0. Then the note adds more context saying this
specific case is probably because there's a null pointer. But the
warning is supposed to be true whether the note is right or not, and
deal with the general case.

>
> BTW, Does --param=min-pagesize=N still work? I couldn't get it to output in a recent test. It lets us et under 0x4000 as invalid addresses.
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106699#c1
>
> Regards
> Jonathan