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From: "drwowe at yahoo dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/52966] New: ill-formed template constexpr functions are accepted?
Date: Thu, 12 Apr 2012 23:45:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52966

             Bug #: 52966
           Summary: ill-formed template constexpr functions are accepted?
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: drwowe@yahoo.com


The following code successfully compiles on g++ 4.7.0 with -std=c++11.  I'm not
a language lawyer, but it seems like it shouldn't since the A::two() function
breaks the constexpr rules, either at template definition or template
instantiation time.

------
template<class T>
struct A {
  static int two_nonconst() { return 2; }
  static constexpr int two() { return two_nonconst(); }
}

constexpr int two() {
  return A<int>::two();
}
------

There is no error message until you actually try to use the two() function in
an appropriate context, which could be very confusing.

------
int x[two()];
------
error: size of array 'x' is not an integral constant-expression