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From: Oleg Petrov <o.petrov@ispras.ru>
To: cocci@inria.fr
Subject: [cocci] devm as drm-init arg: rule with expression finds less than rule with identifier
Date: Fri, 05 Sep 2025 17:06:40 +0300	[thread overview]
Message-ID: <3addf44d4f2524588d664102d5109aad@ispras.ru> (raw)

Hello,

TLDR A rule finds a match with identifier, but not with expression.

I'm using Coccinelle to search for devres-allocated arguments for
drm*init functions. I have a simple rule which seems to work fine:

@badarg exists@
position p,q;
expression devm,e;
@@

devm =@p devm_kzalloc(...);
...
drm_crtc_init_with_planes(@q e,<+...devm...+>,...)

@script:python@
p << badarg.p;
q << badarg.q;
@@
print(p[0].file + ":" + p[0].line + "," + q[0].line)

But then I'd like to find a similar thing, but when another
intermediate variable is used somehow:

@badarg2 exists@
position p,q,r;
expression devm,e;
identifier local;
@@

devm =@p devm_kzalloc(...);
...
local =@r <+...devm...+>;
...
drm_crtc_init_with_planes (@q e,<+...local...+>,...)

@script:python@
p << badarg2.p;
q << badarg2.q;
r << badarg2.r;
@@
print(p[0].file + ":" + p[0].line + "," + r[0].line + "," + q[0].line)

This last rule finds two matches:
drivers/gpu/drm/tilcdc/tilcdc_crtc.c:1005,1018,1031
drivers/gpu/drm/meson/meson_crtc.c:680,686,687

But if I change local to be expression, the rule finds only
drivers/gpu/drm/meson/meson_crtc.c:680,686,687

I wonder, why is that the case? As I understand it, identifier itself
should match expression.

Best regards,
Oleg

next             reply	other threads:[~2025-09-17 12:46 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-05 14:06 Oleg Petrov [this message]
2025-09-23  9:23 ` [cocci] devm as drm-init arg: rule with expression finds less than rule with identifier Oleg Petrov
2025-09-23 13:07 ` Markus Elfring

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