This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 115f. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
2024-12-06
There is implementation divergence with respect to an example like:
constexpr int f(int &r) { r *= 9; return r - 12; }
struct A { int &&temporary; int x; int y; };
constexpr A a1 = { 6, f(a1.temporary), a1.temporary }; // #1
Some implementations accept this code and others say that a1.temporary is not a constant expression in the initializer at #1.
Rationale (July, 2019)
The example is valid; the constant evaluation is the entire initialization constexpr A a1, thus the temporary bound to a1.temporary started its lifetime within the constant evaluation.