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Groups > comp.lang.c++ > #123494

Array size validity and SFINAE

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   #include <iostream>

   struct S { static constexpr int N = -1; };

   template <typename T> void foo(int [T::N])
   {
     std::cout << "array" << std::endl;
   }

   template <typename T> void foo(...)
   {
     std::cout << "..." << std::endl;
   }

   int main()
   {
     foo<int>(0);
   }

GCC outputs "array", Clang and MSVC output "..."

The struct definition can be changed to `struct S {};` with the same 
behavior from GCC. I.e. in template contexts GCC does not check the 
validity of the size specified in array parameter declaration: it 
doesn't care whether it is positive, it doesn't even care whether the 
nested name exists. One can guess that this is most likely a consequence 
of the array parameter type adjustment, which makes the size essentially 
"disappear". However, it still does not necessarily mean that such array 
parameter declaration should be accepted as valid.

So, who's right here standard-wise?

-- 
Best regards,
Andrey

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Array size validity and SFINAE Andrey Tarasevich <noone@noone.net> - 2026-02-25 08:08 -0800
  Re: Array size validity and SFINAE Marcel Mueller <news.5.maazl@spamgourmet.org> - 2026-03-01 16:55 +0100
    Re: Array size validity and SFINAE Andrey Tarasevich <noone@noone.net> - 2026-03-01 08:23 -0800
      Re: Array size validity and SFINAE "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-03-01 16:36 -0800
        Re: Array size validity and SFINAE Andrey Tarasevich <noone@noone.net> - 2026-03-01 16:45 -0800
    Re: Array size validity and SFINAE Bonita Montero <Bonita.Montero@gmail.com> - 2026-03-02 13:21 +0100
  Re: Array size validity and SFINAE Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-02 00:38 -0800
    Re: Array size validity and SFINAE Andrey Tarasevich <noone@noone.net> - 2026-03-02 07:48 -0800
      Re: Array size validity and SFINAE Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-02 21:34 -0800

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