From 2f6a52816fc33cf24373ce2aaf7df08b95403f44 Mon Sep 17 00:00:00 2001 From: Stephane Moore Date: Sat, 21 Sep 2019 01:22:22 +0000 Subject: =?UTF-8?q?[clang-tidy]=20Add=20check=20for=20classes=20missing=20?= =?UTF-8?q?-hash=20=E2=9A=A0=EF=B8=8F?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Summary: Apple documentation states that: "If two objects are equal, they must have the same hash value. This last point is particularly important if you define isEqual: in a subclass and intend to put instances of that subclass into a collection. Make sure you also define hash in your subclass." https://developer.apple.com/documentation/objectivec/1418956-nsobject/1418795-isequal?language=objc In many or all versions of libobjc, -[NSObject isEqual:] is a pointer equality check and -[NSObject hash] returns the messaged object's pointer. A relatively common form of developer error is for a developer to override -isEqual: in a subclass without overriding -hash to ensure that hashes are equal for objects that are equal. It is assumed that an override of -isEqual: is a strong signal for changing the object's equality operator to something other than pointer equality which implies that a missing override of -hash could result in distinct objects being equal but having distinct hashes because they are independent instances. This added check flags classes that override -isEqual: but inherit NSObject's implementation of -hash to warn of the potential for unexpected behavior. The proper implementation of -hash is the responsibility of the developer and the check will only verify that the developer made an effort to properly implement -hash. Developers can set up unit tests to verify that their implementation of -hash is appropriate. Test Notes: Ran check-clang-tools. Reviewers: aaron.ballman, benhamilton Reviewed By: aaron.ballman Subscribers: Eugene.Zelenko, mgorny, xazax.hun, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D67737 llvm-svn: 372445 --- clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp | 3 +++ 1 file changed, 3 insertions(+) (limited to 'clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp') diff --git a/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp b/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp index 636e2c0..c9b57d5 100644 --- a/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp +++ b/clang-tools-extra/clang-tidy/objc/ObjCTidyModule.cpp @@ -12,6 +12,7 @@ #include "AvoidNSErrorInitCheck.h" #include "AvoidSpinlockCheck.h" #include "ForbiddenSubclassingCheck.h" +#include "MissingHashCheck.h" #include "PropertyDeclarationCheck.h" #include "SuperSelfCheck.h" @@ -30,6 +31,8 @@ public: "objc-avoid-spinlock"); CheckFactories.registerCheck( "objc-forbidden-subclassing"); + CheckFactories.registerCheck( + "objc-missing-hash"); CheckFactories.registerCheck( "objc-property-declaration"); CheckFactories.registerCheck( -- cgit v1.1