[cfe-dev] [patch] _Generic constant string used as controlling expression

[Richard Smith]

Looks great, thanks!
On 28 Apr 2014 11:58, "Prathamesh Kulkarni" <bilbotheelffriend at gmail.com>
wrote:

> On Tue, Apr 29, 2014 at 12:06 AM, Richard Smith <richard at metafoo.co.uk>
> wrote:
> > On Mon, Apr 28, 2014 at 11:35 AM, Prathamesh Kulkarni
> > <bilbotheelffriend at gmail.com> wrote:
> >>
> >> On Mon, Apr 28, 2014 at 11:48 PM, Richard Smith <richard at metafoo.co.uk>
> >> wrote:
> >> > On Mon, Apr 28, 2014 at 10:58 AM, Prathamesh Kulkarni
> >> > <bilbotheelffriend at gmail.com> wrote:
> >> >>
> >> >> Hi,
> >> >>    I had reported this bug earlier:
> >> >>
> >> >>
> >> >>
> http://clang-developers.42468.n3.nabble.com/Generic-constant-string-as-controlling-expression-td4036519.html
> >> >>
> >> >> For following case:
> >> >> int main(void)
> >> >> {
> >> >>   int x = _Generic("hello", char *: 1);
> >> >> }
> >> >>
> >> >> clang gives error:
> >> >> generic_expr.c:3:20: error: controlling expression type 'char [6]'
> not
> >> >> compatible with any generic association type
> >> >>  int x = _Generic ("hello", char *: 1);
> >> >>
> >> >> I guess that's because array-to-pointer conversion is not performed
> >> >> when array is used as controlling expression.
> >> >> gcc-4.9 compiles the above test-case.
> >> >>
> >> >> I have attached a patch that performs array-to-pointer conversion
> >> >> when array is used as controlling expression, and it compiles the
> >> >> above test-case.
> >> >> OK to commit ?
> >> >
> >> >
> >> > This isn't quite the right approach -- it will still do the wrong
> thing
> >> > if a
> >> > function designator is used as the argument to _Generic. You should
> use
> >> > DefaultFunctionArrayConversion here instead, replacing the existing
> >> > placeholder handling with it.
> >> Thanks. I modified the patch to call DefaultFunctionArrayConversion.
> >> Is it correct ?
> >
> >
> > No, you still don't handle function types. Please remove the (redundant)
> > handling of placeholder expressions too.
> Sorry, didn't get that earlier.
> The current patch removes handling of placeholder expression and calls
> DefaultFunctionArrayConversion.
>
> Following test-cases compile:
> // check for function-designator
> unsigned foo(void)
> {
>   return 0x03041992;
> }
>
> int main()
> {
>  int x = _Generic (foo, unsigned (*)(void): 1);
>  return x;
> }
>
> // check for array
> int main()
> {
>   int x = _Generic ("hello", char *: 1);
>   return x;
> }
>
> Is this patch correct ?
>
> Thanks and Regards,
> Prathamesh
>
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