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coccinelle: tests: unsigned value cannot be lesser than zero

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Unsigned expressions cannot be lesser than zero. Presence of comparisons
'unsigned (<|<=|>|>=) 0' often indicates a bug, usually wrong type of variable.
The patch beside finding such comparisons tries to eliminate false positives,
mainly by bypassing range checks.

gcc can detect such comparisons also using -Wtype-limits switch, but it warns
also in correct cases, making too much noise.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Michal Marek <mmarek@suse.com>
This commit is contained in:
Andrzej Hajda 2016-01-07 10:36:51 +01:00 committed by Michal Marek
parent 93209d65c1
commit 3f984cb399
1 changed files with 75 additions and 0 deletions
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75
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci Normal file
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/// Unsigned expressions cannot be lesser than zero. Presence of
/// comparisons 'unsigned (<|<=|>|>=) 0' often indicates a bug,
/// usually wrong type of variable.
///
/// To reduce number of false positives following tests have been added:
/// - parts of range checks are skipped, eg. "if (u < 0 || u > 15) ...",
/// developers prefer to keep such code,
/// - comparisons "<= 0" and "> 0" are performed only on results of
/// signed functions/macros,
/// - hardcoded list of signed functions/macros with always non-negative
/// result is used to avoid false positives difficult to detect by other ways
///
// Confidence: Average
// Copyright: (C) 2015 Andrzej Hajda, Samsung Electronics Co., Ltd. GPLv2.
// URL: http://coccinelle.lip6.fr/
// Options: --all-includes
virtual context
virtual org
virtual report
@r_cmp@
position p;
typedef bool, u8, u16, u32, u64;
{unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long,
size_t, bool, u8, u16, u32, u64} v;
expression e;
@@
\( v = e \| &v \)
...
(\( v@p < 0 \| v@p <= 0 \| v@p >= 0 \| v@p > 0 \))
@r@
position r_cmp.p;
typedef s8, s16, s32, s64;
{char, short, int, long, long long, ssize_t, s8, s16, s32, s64} vs;
expression c, e, v;
identifier f !~ "^(ata_id_queue_depth|btrfs_copy_from_user|dma_map_sg|dma_map_sg_attrs|fls|fls64|gameport_time|get_write_extents|nla_len|ntoh24|of_flat_dt_match|of_get_child_count|uart_circ_chars_pending|[A-Z0-9_]+)$";
@@
(
v = f(...)@vs;
... when != v = e;
* (\( v@p <=@e 0 \| v@p >@e 0 \))
... when any
|
(
(\( v@p < 0 \| v@p <= 0 \)) || ... || (\( v >= c \| v > c \))
|
(\( v >= c \| v > c \)) || ... || (\( v@p < 0 \| v@p <= 0 \))
|
(\( v@p >= 0 \| v@p > 0 \)) && ... && (\( v < c \| v <= c \))
|
((\( v < c \| v <= c \) && ... && \( v@p >= 0 \| v@p > 0 \)))
|
* (\( v@p <@e 0 \| v@p >=@e 0 \))
)
)
@script:python depends on org@
p << r_cmp.p;
e << r.e;
@@
msg = "WARNING: Unsigned expression compared with zero: %s" % (e)
coccilib.org.print_todo(p[0], msg)
@script:python depends on report@
p << r_cmp.p;
e << r.e;
@@
msg = "WARNING: Unsigned expression compared with zero: %s" % (e)
coccilib.report.print_report(p[0], msg)