https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103091
Bug ID: 103091
Summary: Can't jump into scope of a variable with a nontrivial
destructor in C++20
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: josephcsible at gmail dot com
Target Milestone: ---
The C++17 standard says "A program that jumps from a point where a variable
with automatic storage duration is not in scope to a point where it is in scope
is ill-formed unless the variable has scalar type, class type with a trivial
default constructor and a trivial destructor, a cv-qualified version of one of
these types, or an array of one of the preceding types and is declared without
an initializer (11.6)."
The C++20 standard says "A program that jumps from a point where a variable
with automatic storage duration is not in scope to a point where it is in scope
is ill-formed unless the variable has vacuous initialization (6.7.3)." and "A
variable is said to have vacuous initialization if it is default-initialized
and, if it is of class type or a (possibly multi-dimensional) array thereof,
that class type has a trivial default constructor."
Note that the C++17 standard mentions a trivial destructor here, but the C++20
standard does not. Now consider this code:
struct MyStruct {
~MyStruct() {}
};
void foo() {
goto x;
MyStruct s;
x:
return;
}
It's ill-formed in C++17, but fine in C++20. However, we currently reject this
program even with -std=c++20.
