https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115233
Bug ID: 115233
Summary: constexpr RVO result is not determined as constant
epression
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: konstantin.vladimirov at gmail dot com
Target Milestone: ---
Consider I have this type:
---
struct Type {
int a;
const int& b;
constexpr Type() : a(1), b(a) {}
};
constexpr Type t1;
constexpr int c11 = t1.a;
constexpr int c12 = t1.b;
---
c11 and c12 are fine for both gcc and clang
Now lets introduce constexpr function which is subject to RVO:
constexpr auto get() {
return Type();
}
Now try this:
constexpr Type t2 = get();
constexpr int c2 = t2.a;
This code compiles fine with clang but not with gcc.
Live example on godbolt: https://godbolt.org/z/zf3YvebbG
According to [expr.const] and [class.copy.elision] result of constexpr function
is necessary RVO and is contant expression, so t2 construction is fine and t2.a
is constant expression as well.
