https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97128
Bug ID: 97128
Summary: Uninitialized members of base class wrongly allowed in
constexpr constructor
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: feodor.alexeev+gcc at gmail dot com
Target Milestone: ---
Given this code: (https://godbolt.org/z/qsaeM7)
struct Base {
int x;
};
struct Derived : Base {
constexpr Derived() { }
};
int main () {
constexpr Derived kDerived;
return kDerived.x;
}
g++ -std=c++17 -pedantic compiles the program that exits with code 0.
clang rejects it as I believe in c++17 for a constructor to be constexpr all
members must be initialized before execution enters the body of the
constructor.
I also believe that the program is invalid as of c++20 as all must be
initialized by the end of the constexpr constructor. Still g++ -std=c++2a
compiles it.
Note that if there was an uninitialized member of Derived itself, g++ would
generate an error as expected.
There is a similar bug filed where g++ wrongly allows uninitialized member of
anonymous struct inside a union member:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86581 . Not sure if this counts as
a duplicate.
