[cfe-commits] [Patch] -Wformat: warn about using length modifiers with %n

Ted Kremenek kremenek at apple.com
Thu Aug 2 10:43:21 PDT 2012

For example:

ll (ell-ell): Specifies that a following d, i, o, u, x, or X conversion specifier applies to a long long int or unsigned long long int argument; or that a following n conversion specifier applies to a pointer to a long long int argument.

On Aug 2, 2012, at 10:31 AM, Ted Kremenek <kremenek at apple.com> wrote:

> C99 says you can use %n with the length modifiers 'hh', 'h', 'l', 'j', 'z', and 't'.
> On Aug 1, 2012, at 6:43 AM, Hans Wennborg <hans at chromium.org> wrote:
>> Hi all,
>> As far as I know, using any length modifier with %n is undefined
>> behavior. For some reason, Clang doesn't think so, but that's probably
>> unintentional? The attached patch makes Clang warn about it.
>> Please take a look.
>> Thanks,
>> Hans
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