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 44virtual org 45virtual report 46 47@cond@ 48statement S1; 49position p; 50@@ 51 52* if@p (...) S1 else S1 53 54@script:python depends on org@ 55p << cond.p; 56@@ 57 58cocci.print_main("WARNING: possible condition with no effect (if == else)",p) 59 60@script:python depends on report@ 61p << cond.p; 62@@ 63 64coccilib.report.print_report(p[0],"WARNING: possible condition with no effect (if == else)") 65