| Nicholas Mc Guire | c899035 | 2016-10-08 17:51:45 +0200 | [diff] [blame] | 1 | ///Find conditions where if and else branch are functionally |
| 2 | // identical. |
| 3 | // |
| 4 | // There can be false positives in cases where the positional |
| 5 | // information is used (as with lockdep) or where the identity |
| 6 | // is a placeholder for not yet handled cases. |
| 7 | // Unfortunately there also seems to be a tendency to use |
| 8 | // the last if else/else as a "default behavior" - which some |
| 9 | // might consider a legitimate coding pattern. From discussion |
| 10 | // on kernelnewbies though it seems that this is not really an |
| 11 | // accepted pattern and if at all it would need to be commented |
| 12 | // |
| 13 | // In the Linux kernel it does not seem to actually report |
| 14 | // false positives except for those that were documented as |
| 15 | // being intentional. |
| 16 | // the two known cases are: |
| 17 | // arch/sh/kernel/traps_64.c:read_opcode() |
| 18 | // } else if ((pc & 1) == 0) { |
| 19 | // /* SHcompact */ |
| 20 | // /* TODO : provide handling for this. We don't really support |
| 21 | // user-mode SHcompact yet, and for a kernel fault, this would |
| 22 | // have to come from a module built for SHcompact. */ |
| 23 | // return -EFAULT; |
| 24 | // } else { |
| 25 | // /* misaligned */ |
| 26 | // return -EFAULT; |
| 27 | // } |
| 28 | // fs/kernfs/file.c:kernfs_fop_open() |
| 29 | // * Both paths of the branch look the same. They're supposed to |
| 30 | // * look that way and give @of->mutex different static lockdep keys. |
| 31 | // */ |
| 32 | // if (has_mmap) |
| 33 | // mutex_init(&of->mutex); |
| 34 | // else |
| 35 | // mutex_init(&of->mutex); |
| 36 | // |
| 37 | // All other cases look like bugs or at least lack of documentation |
| 38 | // |
| 39 | // Confidence: Moderate |
| 40 | // Copyright: (C) 2016 Nicholas Mc Guire, OSADL. GPLv2. |
| 41 | // Comments: |
| 42 | // Options: --no-includes --include-headers |
| 43 | |
| 44 | virtual org |
| 45 | virtual report |
| 46 | |
| 47 | @cond@ |
| 48 | statement S1; |
| 49 | position p; |
| 50 | @@ |
| 51 | |
| 52 | * if@p (...) S1 else S1 |
| 53 | |
| 54 | @script:python depends on org@ |
| 55 | p << cond.p; |
| 56 | @@ |
| 57 | |
| 58 | cocci.print_main("WARNING: possible condition with no effect (if == else)",p) |
| 59 | |
| 60 | @script:python depends on report@ |
| 61 | p << cond.p; |
| 62 | @@ |
| 63 | |
| 64 | coccilib.report.print_report(p[0],"WARNING: possible condition with no effect (if == else)") |