Proverbially Playing the `Devil's Advocate' for Rule 15-1-2

[gs]

The text and rationale of rule 15-1-2 make no mention of the word `macro'. Let us suppose an application made no reference to the Standard Library within it's source code. Consequently, the `NULL' macro has not been defined. Would the following code violate rule 15-1-2?

Code: Select all

class A {};
A NULL;
void f()
    {
    throw NULL;
    }

The very premise of the rationale for the rule is invalid. In this case a `throw NULL;' is not equivalent to `throw (0);' and is not a throwing of an integer expression.

Furthermore, the wording of the rationale is slightly incorrect:

throw(NULL) (equivalent to throw(0)) is never a throw of the null-pointer-constant ...

To quote ISO C++, 18.1, para. 4, (lib.support.types):

The macro NULL is an implementation-defined C++ null pointer constant in this International Standard
(4.10).

Granted, the referenced `4.10' states a null pointer constant has integer (not pointer) type. However, the macro is a null pointer constant.

[misra cpp]

Rule 17-0-2 disallows the reuse of names of standard library MACROs. Reusing NULL is therefore a violation of this rule.