Is (int&&)5 an integral constant expression?

g++ accepts the code:

char b[static_cast<int&&>(5)];

N3936 [expr.const]/3 defines the term as:

An integral constant expression is an expression of integral or unscoped enumeration type, implicitly converted to a prvalue, where the converted expression is a core constant expression. [Note: Such expressions may be used as array bounds [...]

I'm unsure because the expression has type int&& but the definition of integral type in 3.9 doesn't make any mention of reference types.

In case it was unclear, my question is: Is static_cast<int&&>(5) an integral constant expression?

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Background: The question is motivated by the following example:

char *c = (1 - 1);
char *d = static_cast<int&&>(0);

All recent versions of g++ with -std=c++11 accept the c line but reject the d line. The C++11 standard said that a null pointer constant is an integral constant expression with value 0 . (This was changed for C++14).

clang (3.4.1 and later) incorrectly rejects the c line in -std=c++11 mode.

So it appears there is a bug in g++, but I'd like to confirm whether the bug is in the b or the d definition.