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From: "jason at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/51912] New: [C++11] G++ accepts floating point case labels
Date: Fri, 20 Jan 2012 07:46:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51912

             Bug #: 51912
           Summary: [C++11] G++ accepts floating point case labels
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jason@gcc.gnu.org


5.19:  A converted constant expression of type T is a literal constant
expression, implicitly converted to type T, where the implicit conversion (if
any) is permitted in a literal constant expression and the implicit conversion
sequence contains only user-defined  conversions, lvalue-to-rvalue conversions
(4.1), integral promotions (4.5), and integral conversions (4.7) other than
narrowing conversions (8.5.4). [ Note: such expressions may be used as case
expressions (6.4.2), ....

So a floating point literal is not a valid case expression, since converting it
to the switch type would require a non-integral conversion.

void f(int i)
{
  switch (i)
    {
    case 1.0:;
    }
}