Re: format string is not a string literal

Jack Howarth
2015-02-26T08:39:38Z

On Wed, Feb 25, 2015 at 9:38 PM, Andrew Pinski <pinskia@gmail.com> wrote:
> On Wed, Feb 25, 2015 at 6:35 PM, Andrew Pinski <pinskia@gmail.com> wrote:
>> On Wed, Feb 25, 2015 at 6:30 PM, Simon Marchi <simon.marchi@polymtl.ca> wrote:
>>>>> 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
>>>
>>> I would not say that clang is broken or that the warning is unclear.
>>> The flag is -Wformat-nonliteral and the warning message is "format
>>> string is not a string literal". I don't know how you can be more
>>> clear and direct about the fact that the format string is not a string
>>> literal. Looking at the code, we observe that clang is right (the
>>> format string is indeed not a string literal). With the proper
>>> function attributes, the compiler could do better checks and prevent
>>> programming mistakes. Since clang pointed out this low-hanging fruit
>>> improvement to gdb's code, why shouldn't we take advantage of it?
>>>
>>> Anyway, Jack, you are welcome to submit a patch for this if you feel
>>> like it and/or file a bug if it is not already done.
>>
>>
>> Except GCC documents this options differently than clang implements:
>> -Wformat-nonliteralIf -Wformat is specified, also warn if the format
>> string is not a string literal and so cannot be checked, unless the
>> format function takes its format arguments as a va_list.
>>
>>
>> Notice the last part of the documentation.
>>
>> So this again is clang implements a GCC option but does not follow the
>> documentation of GCC.
>> How does clang document this option?
>>
>
> GCC has always documented this option this way since at least 3.1.1:
> https://gcc.gnu.org/onlinedocs/gcc-3.1.1/gcc/Warning-Options.html#Warning%20Options
>
> And there is no user documentation for clang for this option so clang is broken.

http://clang.llvm.org/docs/AttributeReference.html#format-gnu-format

>
> Thanks,
> Andrew
>
>
>
>> Thanks,
>> Andrew
>>
>>>
>>> Simon