[Bug tree-optimization/113664] False positive warnings with -fno-strict-overflow (-Warray-bounds, -Wstringop-overflow)

["stefan at bytereef dot org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113664

--- Comment #5 from Stefan Krah <stefan at bytereef dot org> ---
> So the diagnostic messages leave a lot to be desired but in the end
> they point to a problem in your code which is a guard against a NULL 's'.

Hmm, the real code is used to print floating point numbers and integers.
Integers get dot==NULL. It is fine (and desired!) in that case to optimize
away the if clause.

As far as I can see, it is compliant with the C standard.


Even with -fno-strict-overflow one could make the case that the warning
is strange. If "s" wraps around, the allocated output string is too small,
and you have bigger problems.

It is impossible for gcc to detect whether the string size is sufficient,
so IMHO it should not warn.


In essence, since gcc-10 (12?) idioms that were warning-free for 10 years
tend to receive false positive warnings now.

This also applies to -Warray-bounds. I think the Linux kernel disables at
least -Warray-bounds and -Wmaybe-uninitialized.

I think this is becoming a problem, because most projects do not report
false positives but just silently disable the warnings.