patchcocci: drop bogus xstrdup_or_null() rule

13092a91 (cocci: refactor common patterns to use xstrdup_or_null(), 2016-10-12) introduced a rule to rewrite this conditional call to xstrdup(E) and an assignment to variable V:

    - if (E)
    -    V = xstrdup(E);

into an unconditional call to xstrdup_or_null(E) and an assignment to variable V:

    + V = xstrdup_or_null(E);

which is utterly bogus. The original code may already have an acceptable value in V and the conditional assignment may be to improve the value already in V with a copy of a better value E when (and only when) E is not NULL.

The rewritten construct unconditionally discards the existing value of V and replaces it with a copy of E, even when E is NULL, which changes the meaning of the program.

By the way, if it were

	-if (E && !V)
	-	V = xstrdup(E);
	+V = xstrdup_or_null(E);

it would probably have been correct. But there is no existing code that would have been improved by such a rule, so let's just remove the bogus one without replacing with the more specific one.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 contrib/coccinelle/xstrdup_or_null.cocci | 8 --------
 1 file changed, 8 deletions(-)

On 5/1/2022 1:00 AM, Junio C Hamano wrote:

Yes, this makes sense.
 

I think you mean if it were

	-if (E && !V)
	-	V = xstrdup(E);
	+if (!V)
	+	V = xstrdup_or_null(E);

or

	-if (E && !V)
	-	V = xstrdup(E);
	+free(V);
	+V = xstrdup_or_null(E);

But yes, there is no preimage matching this pattern, so it doesn't matter.

Dropping the rule makes the most sense.

Thanks, -Stolee

Derrick Stolee <derrickstolee@github.com> writes:

Please disregard.  That one was completely bogus.

Yup.  ThHanks for a doze of sanity.