问题
$4.2/1 - "An lvalue or rvalue of type “array ofN T” or “array of unknown bound of T” can be converted to an rvalue of type “pointer to T.” The result is a pointer to the first element of the array."
I am not sure how do we get an rvalue of an array type other than during initialization/declaration?
回答1:
I'm not sure what you refer to by "initialization/declaration" in this context. In the following, the array is a prvalue
template<typename T> using alias = T;
int main() { return alias<int[]>{1, 2, 3}[0]; }
This can be verified by decltype(alias<int[]>{1, 2, 3}) having the type int[3]. Creating arrays this way on the fly wasn't initially intended to work but slipped into the working draft by-the-way of related work on uniform initialization. When I realized that some paragraphs in the C++0x working draft disallow some special case of this on-the-fly creation of array temporaries while other paragraphs allow it, I sent a defect report to the C++ committee, which then on the basis of GCC's partially working implementation decided to fully support this.
回答2:
You cannot get an rvalue of array type. Arrays can only be lvalues, and whenever they are used in an lvalue they decay to a pointer to the first element.
int array[10];
int * p = array; // [1]
The expression array in [1] is an lvalue of type int (&)[10] that gets converted to an rvalue of type int *p, that is, the rvalue array of N==10 T==int is converted to an lvalue of type pointer to T==int.
回答3:
Would this stand a chance to demonstrate Array Rvalue?
int main(){
int buf[10][10];
int (*p)[10] = buf;
int (*p2)[10] = p; // LValue to Rvalue conversion of Array type 'p'
}
来源：https://stackoverflow.com/questions/3656726/array-and-rvalue