Re: format string is not a string literal

[pinskia at gmail dot com]

> On Feb 25, 2015, at 4:41 PM, Jack Howarth <howarth.mailing.lists@gmail.com> wrote:
> 
> Andrew,
>     See the additional comments from the llvm.org clang developers at...
> 
> http://llvm.org/bugs/show_bug.cgi?id=22701#c5

Then put this warning under a different flag. Anyways clang is broken and gdb should not change due to a broken compiler. 

Thanks,
Andrew


> 
>         Jack
> 
>> On Wed, Feb 25, 2015 at 7:12 PM,  <pinskia@gmail.com> wrote:
>> 
>> 
>> 
>> 
>> On Feb 25, 2015, at 4:05 PM, Simon Marchi <simon.marchi@polymtl.ca> wrote:
>> 
>>>> I didnât say itâs a bug, Andrew did.  But I agree with him.
>>>> 
>>>> My comment (âthe code is legitâ) simply meant that GDB uses variable formats for obvious valid reasons (so the format can vary, being user-supplied).  Given that itâs intentional, the warning is not wanted.
>>>> 
>>>> But that point is really applicable to printf, not vprintf.  Andrewâs point is that checking formats for vprintf is not possible because you canât know the argument list; only in printf do you see the arguments so you can match the types.  So the bug is that format checking and complaining for non-literal formats should not be enabled at all for vprintf.  That may be a header issue rather than a compiler issue, but either way, itâs not the right thing to do.
>>>> 
>>>>       paul
>>> 
>>> I think the warning is relevant. If you instruct the compiler that
>>> inferior_debug takes a format string and format arguments (using a
>>> format attribute, as mentioned by Richard in the bug report), then it
>>> can check if the callers are doing something wrong.
>>> 
>>> In the case of inferior_debug, the attribute should be
>>>   __attribute__((format (printf, 2, 3)))
>>> 
>>> By adding the attribute, you get nice warnings of this kind:
>>> 
>>> test.c: In function âmainâ:
>>> test.c:17:2: warning: too many arguments for format [-Wformat-extra-args]
>>> inferior_debug (1, "pouet %d", 2, "hello");
>>> 
>>> If the function is vprintf-style, it's similar but the last argument
>>> should be 0. It will push the argument check a level higher, where
>>> eventually they are explicitely defined printf-style. The doc is
>>> somewhere here [2] in the middle.
>> 
>> Then clang's warning should suggest putting the format attribute on that function rather than giving out a warning that seems like it is a bogus one.
>> 
>> Gcc does that iirc why not clang.
>> 
>> Thanks,
>> Andrew
>> 
>> 
>>> 
>>> The warning also has some value because it will tell you if the string
>>> originally comes from a non-literal, which should be avoided [1].
>>> 
>>> [1] http://en.wikipedia.org/wiki/Uncontrolled_format_string
>>> [2] https://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
>>> 
>>> Simon