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 45virtual org 46virtual report 47 48@cond@ 49statement S1; 50position p; 51@@ 52 53* if@p (...) S1 else S1 54 55@script:python depends on org@ 56p << cond.p; 57@@ 58 59cocci.print_main("WARNING: possible condition with no effect (if == else)",p) 60 61@script:python depends on report@ 62p << cond.p; 63@@ 64 65coccilib.report.print_report(p[0],"WARNING: possible condition with no effect (if == else)") 66