r201162 - 'nonnull(1)' on a block parameter should apply to the block's argument.

[Ted Kremenek]

Since this attribute hasn’t been available before in this position (except in GCC), I think exploring an alternate spelling is interesting.  What would you propose?

On Feb 17, 2014, at 4:41 PM, Richard Smith <metafoo at gmail.com> wrote:

> Yeah, I think that'd mostly work. But be careful about this case:
> 
> template<typename T>
> void f(T *p __attribute__((nonnull))) {
>   p(0); // #1
> }
> void g() { f<void(int *q)>(0); } // #2
> 
> Here again, GCC warns on #1 and Clang warns on #2. If we want to keep 'nonnull' as the spelling for this new thing, I think we should keep warning on #2. (But I do wonder if we should come up with a new name for this, rather than picking something that collides with an existing GCC attribute, even if only in corner cases.)
> 
> On Mon Feb 17 2014 at 4:21:49 PM, Jordan Rose <jordan_rose at apple.com> wrote:
> +Ted.
> 
> I'm guessing we should stick with GCC's interpretation when the parameter is a function or block pointer, but maybe have a warning, and a fix-it for both possible interpretations.
> 
> Jordan
> 
> 
> On Feb 17, 2014, at 15:52, Richard Smith <metafoo at gmail.com> wrote:
> 
>> This still seems to be GCC-incompatible. Per the GCC documentation, "__attribute__((nonnull))" on a pointer-to-function parameter means that all of *that* function's parameters can't be null. For instance:
>> 
>> void f(int (*p)(int *a, int *b) __attribute__((nonnull))) {
>>   if (p)
>>     p(0, 0); // #1
>> }
>> void g() { f(0); } // #2
>> 
>> GCC warns on line #1, Clang warns on line #2.
>> 
>> On Tue Feb 11 2014 at 9:40:01 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
>> On Tue, Feb 11, 2014 at 12:37 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>> >
>> > On Feb 11, 2014, at 9:36 , Aaron Ballman <aaron at aaronballman.com> wrote:
>> >
>> > +    if (D->getFunctionType()) {
>> > +      handleNonNullAttr(S, D, Attr);
>> > +    } else {
>> > +      S.Diag(Attr.getLoc(), diag::warn_attribute_nonnull_parm_no_args)
>> > +        << D->getSourceRange();
>> > +    }
>> >
>> >
>> > Minor nit about the style -- shouldn't be using the curly braces here.
>> >
>> >
>> > Uh...hm. I tried it without the curly braces, but it looked very strange
>> > with the << dangling there. Should I add a dummy comment to justify it?
>> 
>> I'm not too keen on dummy comments. If you think it's ugly without the
>> braces, I'm fine with leaving them. :-)
>> 
>> ~Aaron
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> 
> 

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