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From: "thomas.sanchz at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/59435] New: sizeof...(T) as default value for an argument does not work
Date: Mon, 09 Dec 2013 16:33:00 -0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 4.8.1
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59435

            Bug ID: 59435
           Summary: sizeof...(T) as default value for an argument does not
                    work
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: thomas.sanchz at gmail dot com

Hi everybody,

I encountered something not supported in gcc from 4.7 to 4.9, but working in
clang from 3.2 (tested on gcc goldbot).

Here is the code:

template <typename... E>
struct T
{
  T(unsigned int i = sizeof...(E)){} // does not compile

  static constexpr unsigned int U = sizeof...(E);
  T(unsigned int j, unsigned int i = U){} //  compile
};

template <typename... T>
void test(int i = sizeof...(T)) // compile
{}

Invocation with "g++ -std=c++11 test.cpp" is enough to reproduce the bug.

Please let me know if you need more information.

Cheers,