e77b48b0 - Implement -Watomic-implicit-seq-cst

Mon, 10 Sep 2018 20:42:56 +0000

Implement -Watomic-implicit-seq-cstSummary:_Atomic and __sync_* operations are implicitly sequentially-consistent. Somecodebases want to force explicit usage of memory order instead. This warningallows them to know where implicit sequentially-consistent memory order is used.The warning isn't on by default because _Atomic was purposefully designed tohave seq_cst as the default: the idea was that it's the right thing to use mostof the time. This warning allows developers who disagree to enforce explicitusage instead.A follow-up patch will take care of C++'s std::atomic. It'll be different enoughfrom this patch that I think it should be separate: for C++ the atomicoperations all have a memory order parameter (or two), but it's defaulted. Ibelieve this warning should trigger when the default is used, but not whenseq_cst is used explicitly (or implicitly as the failure order for cmpxchg).Reviewers: rjmccallSubscribers: dexonsmith, cfe-commitsDifferential Revision: https://reviews.llvm.org/D51084llvm-svn: 341860 List of files: /llvm-project-15.0.7/clang/test/Sema/sync-implicit-seq_cst.c

Changes in sync-implicit-seq_cst.c

e77b48b0 - Implement -Watomic-implicit-seq-cst