[cfe-dev] RFC: Nullability qualifiers

[Daniel Marjamäki]

Hello!

Marshall Clow wrote:

> After executing this code, what will the value of p3 be?
> Under gcc/glibc, it will be NULL, because memcpy is marked with non-null attributes, and so the if (p==NULL) branch is removed.
> (Yes, even though memcpy(x, y, 0) will not dereference the pointer)

This is undefined behaviour right?

The C standard says that all the memcpy arguments must be valid according to 7.1.4.. and there we have this text:

.... unless explicitly stated otherwise in the detailed descriptions that follow: If an argument to a function has an invalid value (.... or a null pointer, ...) .., the behavior is undefined.

It seems to me that it says that passing a null pointer to any C standard library function is undefined behaviour, unless it's explicitly stated otherwise.

Best regards,
Daniel Marjamäki