[Bug c/65446] Improve -Wformat-signedness

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65446

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-06-09
                 CC|                            |manu at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #6 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Ricardo Nabinger Sanchez from comment #5)
> In short: please warn.  Some cases will generate unexpected results (which
> are not compilation errors), simply because the programmer used an incorrect
> format specifier.

I think there is no doubt that we want to warn in cases that lead to different
output (%u + short) or UB and avoid warning in cases that do not have any
effect (%u + unsigned short).

The question is how and who will implement these heuristics:
https://gcc.gnu.org/wiki/GettingStarted#Basics:_Contributing_to_GCC_in_10_easy_steps

You are welcome to try. All the relevant code is in
https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/c-family/c-format.c;h=c19c411d61a44773c55c8686802787ec7e4c40a4;hb=HEAD