Hello all. Is the following valid C++0x?

void g(...) { }

template<typename ...T>
void f(T...) {
 g([] {
     std::cout << sizeof(T) << std::endl;
     return 0;
   }()...
 );
}

The lambda appears in an initializer-list, so i thought it's a valid context
for pack-expansion, but GCC4.5 complains with

 "error: parameter packs not expanded with '...'"

Any Standard paragraph forbidding that?

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"Johannes Schaub (litb)" <schaub-johannes@web.de> writes:

> Hello all. Is the following valid C++0x?
>
> void g(...) { }
>
> template<typename ...T>
> void f(T...) {
>  g([] {
>      std::cout << sizeof(T) << std::endl;
>      return 0;
>    }()...
>  );
> }
>
> The lambda appears in an initializer-list, so i thought it's a valid
context
> for pack-expansion, but GCC4.5 complains with
>
>  "error: parameter packs not expanded with '...'"
>
> Any Standard paragraph forbidding that?
>
> --
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This does not answer your question specifically but, as I far as I am
aware, GCC still has an incomplete implementation of variadics, with
4.5.0 exhibiting continuing issues along the lines of those discussed at
http://stackoverflow.com/questions/1989552/gcc-error-with-variadic-templates-sorry-unimplemented-cannot-expand-identif
,
a thread to which, I notice, you yourself contributed.  I might have
expected the error message to have been different if it was a related
issue, but it could present a complication affecting what might otherwise
be expected to work.

Regards

Paul Bibbings

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Johannes Schaub (litb) wrote:

> Hello all. Is the following valid C++0x?
>
> void g(...) { }
>
> template<typename ...T>
> void f(T...) {
>  g([] {
>     std::cout << sizeof(T) << std::endl;
>     return 0;
>   }()...
>  );
> }
>

I'm not considering whether it is correct by the Standard, or if it
is what you wanted, but moving "..." right after sizeof will produce
compilable code.

std::cout << sizeof...(T) << std::endl;

--
Dragan

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