Does Rule 11.9 allow indirect expansion from NULL?

Does Rule 11.9 allow indirect expansion from NULL? - Printable Version

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Does Rule 11.9 allow indirect expansion from NULL? - rgamble - 14-09-2016

Does the following example violate Rule 11.9?

Code:
#define FOO NULL

int32_t *p1 = FOO;

Re: Does Rule 11.9 allow indirect expansion from NULL? - dg1980 - 15-09-2016

rgamble Wrote:Does the following example violate Rule 11.9?

Code:
#define FOO NULL int32_t *p1 = FOO;

There is a note in rule 11.9 that says:

Quote:a null pointer constant of the form (void*)0 is permitted, whether or not it was expanded from NULL

There is also the following sample code:

Code:
#define MY_NULL_2 (void*)0

if (p2 == MY_NULL_2)/*compliant*/

Given the fact that this is identical with your example after preprocessing stage, logic dictates it cannot be a violation.

Re: Does Rule 11.9 allow indirect expansion from NULL? - delta_controls - 15-09-2016

I don't think it is a violation. However, the intention of the rule is to increase clarity and your macro reduces clarity.

The note is not relevant to your example.

The compliant example given by @dg1980 is not necessarily identical, as the actual expansion of the NULL macro is implementation-defined.

Re: Does Rule 11.9 allow indirect expansion from NULL? - misra-c - 23-09-2016

Your example does not violate rule 11.9 as the value is derived from NULL.

Rule 11.9 permits "NULL", (void *)0 and any macros that expand to these values.