git/contrib/coccinelle/unused.cocci
Ævar Arnfjörð Bjarmason 06f5f8940c cocci: generalize "unused" rule to cover more than "strbuf"
Generalize the newly added "unused.cocci" rule to find more than just
"struct strbuf", let's have it find the same unused patterns for
"struct string_list", as well as other code that uses
similar-looking *_{release,clear,free}() and {release,clear,free}_*()
functions.

We're intentionally loose in accepting e.g. a "strbuf_init(&sb)"
followed by a "string_list_clear(&sb, 0)".  It's assumed that the
compiler will catch any such invalid code, i.e. that our
constructors/destructors don't take a "void *".

See [1] for example of code that would be covered by the
"get_worktrees()" part of this rule. We'd still need work that the
series is based on (we were passing "worktrees" to a function), but
could now do the change in [1] automatically.

1. https://lore.kernel.org/git/Yq6eJFUPPTv%2Fzc0o@coredump.intra.peff.net/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-07-06 12:24:43 -07:00

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// This rule finds sequences of "unused" declerations and uses of a
// variable, where "unused" is defined to include only calling the
// equivalent of alloc, init & free functions on the variable.
@@
type T;
identifier I;
// STRBUF_INIT, but also e.g. STRING_LIST_INIT_DUP (so no anchoring)
constant INIT_MACRO =~ "_INIT";
identifier MALLOC1 =~ "^x?[mc]alloc$";
identifier INIT_ASSIGN1 =~ "^get_worktrees$";
identifier INIT_CALL1 =~ "^[a-z_]*_init$";
identifier REL1 =~ "^[a-z_]*_(release|reset|clear|free)$";
identifier REL2 =~ "^(release|clear|free)_[a-z_]*$";
@@
(
- T I;
|
- T I = { 0 };
|
- T I = INIT_MACRO;
|
- T I = MALLOC1(...);
|
- T I = INIT_ASSIGN1(...);
)
<... when != \( I \| &I \)
(
- \( INIT_CALL1 \)( \( I \| &I \), ...);
|
- I = \( INIT_ASSIGN1 \)(...);
|
- I = MALLOC1(...);
)
...>
(
- \( REL1 \| REL2 \)( \( I \| &I \), ...);
|
- \( REL1 \| REL2 \)( \( &I \| I \) );
)
... when != \( I \| &I \)