* [PATCH] cocci: drop bogus xstrdup_or_null() rule
@ 2022-05-01 5:00 Junio C Hamano
2022-05-02 13:46 ` Derrick Stolee
0 siblings, 1 reply; 3+ messages in thread
From: Junio C Hamano @ 2022-05-01 5:00 UTC (permalink / raw)
To: git
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(-)
diff --git a/contrib/coccinelle/xstrdup_or_null.cocci b/contrib/coccinelle/xstrdup_or_null.cocci
index 8e05d1ca4b..9c1d2939b6 100644
--- a/contrib/coccinelle/xstrdup_or_null.cocci
+++ b/contrib/coccinelle/xstrdup_or_null.cocci
@@ -1,11 +1,3 @@
-@@
-expression E;
-expression V;
-@@
-- if (E)
-- V = xstrdup(E);
-+ V = xstrdup_or_null(E);
-
@@
expression E;
@@
--
2.36.0-233-gea8f06b421
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] cocci: drop bogus xstrdup_or_null() rule
2022-05-01 5:00 [PATCH] cocci: drop bogus xstrdup_or_null() rule Junio C Hamano
@ 2022-05-02 13:46 ` Derrick Stolee
2022-05-02 17:07 ` Junio C Hamano
0 siblings, 1 reply; 3+ messages in thread
From: Derrick Stolee @ 2022-05-02 13:46 UTC (permalink / raw)
To: Junio C Hamano, git
On 5/1/2022 1:00 AM, Junio C Hamano wrote:
> 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.
Yes, this makes sense.
> 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);
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
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] cocci: drop bogus xstrdup_or_null() rule
2022-05-02 13:46 ` Derrick Stolee
@ 2022-05-02 17:07 ` Junio C Hamano
0 siblings, 0 replies; 3+ messages in thread
From: Junio C Hamano @ 2022-05-02 17:07 UTC (permalink / raw)
To: Derrick Stolee; +Cc: git
Derrick Stolee <derrickstolee@github.com> writes:
> I think you mean if it were
> ...
Please disregard. That one was completely bogus.
> Dropping the rule makes the most sense.
Yup. ThHanks for a doze of sanity.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-05-02 17:08 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2022-05-01 5:00 [PATCH] cocci: drop bogus xstrdup_or_null() rule Junio C Hamano
2022-05-02 13:46 ` Derrick Stolee
2022-05-02 17:07 ` Junio C Hamano
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