https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108993
Bug ID: 108993
Summary: Value initialization does not occur for derived class
with -Os, for gcc versions > 5
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: daniel.gotsch at bluerivertech dot com
Target Milestone: ---
Minimal example:
#include <iostream>
struct Base {
Base() {} // not a default constructor
double x;
};
struct Derived : public Base {
Derived() = default; // default constructor should lead to
zero-initialization
};
int main () {
Base a{};
std::cout << a.x; // Could be any value
Derived b{};
std::cout << b.x; // Should be set 0 but isn't set 0 when compiled with -Os
flag
}
see compiler output https://godbolt.org/z/Ecr1K9cMM
The class Derived has a default constructor which satisfies (2) of
value-initalization meaning the object should be zero-initialized.
see https://en.cppreference.com/w/cpp/language/value_initialization
Zero-initialization should zero-out the base class too, see
https://en.cppreference.com/w/cpp/language/zero_initialization
