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+---- Thread: Clarification Rule 0.2.1 (/showthread.php?tid=1779)
Clarification Rule 0.2.1 - hahn - 27-08-2026
Hi,
I have a question regarding rule 0.2.1 on the following code:
Code:
namespace {
struct Base {
Base() {
// do resource management
}
};
struct Derived : public Base {
// has implicit default constructor that calls user-provided Base()
};
Base b; // (1) compliant
Derived d; // (2) compliant or non-compliant for rule 0.2.1 ?
}Case (1) is clearly compliant as b has class type Base and Base has a user-provided constructor.
Case (2) is unclear, as the default constructor of Derived is not user-provided, if I understand the C++ standard correctly, as the user does not declare it at all.
Still case (2) seems fine and in line with the rule's rationale.
It would be great to get a clarification whether case (2) is considered compliant or not, and if compliant, what the intended definition of "use" should be.
Thanks a lot!
RE: Clarification Rule 0.2.1 - misra cpp - 28-08-2026
You're right, the intent of 0.2.1 was that 'd' in you example should be compliant, but a strict reading of the rule says its not.
The problem is the last paragraph in the rule: "The variable is of class type and has a user-provided constructor or a user-provided destructor.". The two occurrences of 'user-provided' should be 'non-trivial'. This has been noted for future revision.
In the short term, you can either deviate or provide an explicit constructor for Devired.