[Bug middle-end/79448] unhelpful -Wformat-truncation=2 INT_MAX warning

[mark at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79448

--- Comment #5 from Mark Wielaard <mark at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #4)
> Ouch.  When its size argument is zero, a snprintf call is a request to
> compute the size of output without actually writing any into the destination
> (which may be a null pointer).  At level 2 the checker uses the lower bound
> of the range of the size argument (for greater strictness) but fails to
> distinguish it from a constant zero.  Since the argument may or may not be
> zero this is not safe.  I've raised bug 79496 to track the problem (which is
> unrelated to this bug).

Thanks for fixing that bug.

I fetch the latest gcc svn trunk with that fix and added your proposed patch
for this bug on top and I no longer get false positives with
-Wformat-truncation=2 on my code base and all unit tests pass now. The only
warnings reported (with this patch applied) are cases where there is indeed a
possibility of truncation that wasn't handled in the code.

So if at all possible I would like to see this go in before gcc 7.1 is released
because without it -Wformat-truncation=2 isn't as useful as it could be.