http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57979
Bug ID: 57979
Summary: G++ accepts constant expression defined using floating
point glvalue
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jogojapan at gmail dot com
The following code is accepted and compiled without error by G++:
int main()
{
const float f1 = 0.0;
constexpr float f2 = f1;
return 0;
}
Note that the declaration of f2 as constexpr requires f1 to be a constant
expression, which it isn't, according to ยง5.19/2:
====(QUOTE)========
A condition-expression is a core constant expression unless it involves
[...]
[..9th item..]
- an lvalue-to-rvalue conversion (4.1) unless it is applied to [...] a glvalue
of integral or enumeration type that refers to a non-volatile const object with
a preceding initialization, initialized with a constant expresion, or
[...]
====(ENDQUOTE)====
So if f1 had been declared as const int, the code would be acceptable, but
there is no such exception for floating point (or any other non-integral or
non-enum type).
Tested with a 20130708 snapshot checkout from the master branch of the
git-mirror of the repository. (I'll test with a more recent version soon.)
