name : cond_no_effect.cocci // SPDX-License-Identifier: GPL-2.0-only ///Find conditions where if and else branch are functionally // identical. // // There can be false positives in cases where the positional // information is used (as with lockdep) or where the identity // is a placeholder for not yet handled cases. // Unfortunately there also seems to be a tendency to use // the last if else/else as a "default behavior" - which some // might consider a legitimate coding pattern. From discussion // on kernelnewbies though it seems that this is not really an // accepted pattern and if at all it would need to be commented // // In the Linux kernel it does not seem to actually report // false positives except for those that were documented as // being intentional. // the two known cases are: // arch/sh/kernel/traps_64.c:read_opcode() // } else if ((pc & 1) == 0) { // /* SHcompact */ // /* TODO : provide handling for this. We don't really support // user-mode SHcompact yet, and for a kernel fault, this would // have to come from a module built for SHcompact. */ // return -EFAULT; // } else { // /* misaligned */ // return -EFAULT; // } // fs/kernfs/file.c:kernfs_fop_open() // * Both paths of the branch look the same. They're supposed to // * look that way and give @of->mutex different static lockdep keys. // */ // if (has_mmap) // mutex_init(&of->mutex); // else // mutex_init(&of->mutex); // // All other cases look like bugs or at least lack of documentation // // Confidence: Moderate // Copyright: (C) 2016 Nicholas Mc Guire, OSADL. // Comments: // Options: --no-includes --include-headers virtual org virtual report @cond@ statement S1; position p; @@ * if@p (...) S1 else S1 @script:python depends on org@ p << cond.p; @@ cocci.print_main("WARNING: possible condition with no effect (if == else)",p) @script:python depends on report@ p << cond.p; @@ coccilib.report.print_report(p[0],"WARNING: possible condition with no effect (if == else)")