http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52257
Bug #: 52257
Summary: [C++11] switch cases accept floating point constants
Classification: Unclassified
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: [email protected]
ReportedBy: [email protected]
gcc 4.7.0 20120211 (experimental) accepts the following program, when using
-std=c++11 (with or without -Wall -pedantic):
int main()
{
int i = 3;
switch (i) {
case 2: ;
case 3.7: ;
}
}
The program is correctly rejected when compiling w/o -std=c++11.
Nonetheless, a C++11 compiler has to reject this code. We have [stmt.switch]
p2:
"[..] Any statement within the switch statement can be labeled with one or more
case labels as follows:
case constant-expression :
where the constant-expression shall be a converted constant expression (5.19)
of the promoted type of the switch condition.[..]"
According to [expr.const] p3 we have:
"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)."
This clearly excludes floating-integral conversions from 4.9 [conv.fpint].
