1 // SPDX-License-Identifier: GPL-2.0-only
2 ///Find conditions where if and else branch are functionally
3 // identical.
4 //
5 // There can be false positives in cases where the positional
6 // information is used (as with lockdep) or where the identity
7 // is a placeholder for not yet handled cases.
8 // Unfortunately there also seems to be a tendency to use
9 // the last if else/else as a "default behavior" - which some
10 // might consider a legitimate coding pattern. From discussion
11 // on kernelnewbies though it seems that this is not really an
12 // accepted pattern and if at all it would need to be commented
13 //
14 // In the Linux kernel it does not seem to actually report
15 // false positives except for those that were documented as
16 // being intentional.
17 // the two known cases are:
18 // arch/sh/kernel/traps_64.c:read_opcode()
19 // } else if ((pc & 1) == 0) {
20 // /* SHcompact */
21 // /* TODO : provide handling for this. We don't really support
22 // user-mode SHcompact yet, and for a kernel fault, this would
23 // have to come from a module built for SHcompact. */
24 // return -EFAULT;
25 // } else {
26 // /* misaligned */
27 // return -EFAULT;
28 // }
29 // fs/kernfs/file.c:kernfs_fop_open()
30 // * Both paths of the branch look the same. They're supposed to
31 // * look that way and give @of->mutex different static lockdep keys.
32 // */
33 // if (has_mmap)
34 // mutex_init(&of->mutex);
35 // else
36 // mutex_init(&of->mutex);
37 //
38 // All other cases look like bugs or at least lack of documentation
39 //
40 // Confidence: Moderate
41 // Copyright: (C) 2016 Nicholas Mc Guire, OSADL.
42 // Comments:
43 // Options: --no-includes --include-headers
44
45 virtual org
46 virtual report
47
48 @cond@
49 statement S1;
50 position p;
51 @@
52
53 * if@p (...) S1 else S1
54
55 @script:python depends on org@
56 p << cond.p;
57 @@
58
59 cocci.print_main("WARNING: possible condition with no effect (if == else)",p)
60
61 @script:python depends on report@
62 p << cond.p;
63 @@
64
65 coccilib.report.print_report(p[0],"WARNING: possible condition with no effect (if == else)")
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