From ce2b40def1765832ac505033bf24a78fe85d06f9 Mon Sep 17 00:00:00 2001 From: Sam McCall Date: Fri, 15 Feb 2019 07:16:11 +0000 Subject: [PATCH] [Analysis] -Wunreachable-code shouldn't fire on the increment of a foreach loop Summary: The idea is that the code here isn't written, so doesn't indicate a bug. Similar to code expanded from macros. This means the warning no longer fires on this code: for (auto C : collection) { process(C); return; } handleEmptyCollection(); Unclear whether this is more often a bug or not in practice, I think it's a reasonable idiom in some cases. Either way, if we want to warn on "loop that doesn't loop", I think it should be a separate warning, and catch `while(1) break;` Reviewers: ilya-biryukov, ioeric Subscribers: cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D58134 llvm-svn: 354102 --- clang/lib/Analysis/ReachableCode.cpp | 4 ++++ clang/test/SemaCXX/unreachable-code.cpp | 5 +++++ 2 files changed, 9 insertions(+) diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp index cc64efa7f07f..6f1814deb00b 100644 --- a/clang/lib/Analysis/ReachableCode.cpp +++ b/clang/lib/Analysis/ReachableCode.cpp @@ -631,6 +631,10 @@ void DeadCodeScan::reportDeadCode(const CFGBlock *B, // a for/for-range loop. This is the block that contains // the increment code. if (const Stmt *LoopTarget = B->getLoopTarget()) { + // The increment on a foreach statement is not written. + if (isa(LoopTarget)) + return; + SourceLocation Loc = LoopTarget->getBeginLoc(); SourceRange R1(Loc, Loc), R2; diff --git a/clang/test/SemaCXX/unreachable-code.cpp b/clang/test/SemaCXX/unreachable-code.cpp index fd006c099e7d..61805837dc29 100644 --- a/clang/test/SemaCXX/unreachable-code.cpp +++ b/clang/test/SemaCXX/unreachable-code.cpp @@ -52,6 +52,11 @@ void test3() { } } +void test4() { + for (char c : "abc") // no-warning + break; +} + // PR 6130 - Don't warn about bogus unreachable code with throw's and // temporary objects. class PR6130 {