Author: sammccall
Date: Thu Feb 14 23:16:11 2019
New Revision: 354102
URL: http://llvm.org/viewvc/llvm-project?rev=354102&view=rev
Log:
[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
Modified:
cfe/trunk/lib/Analysis/ReachableCode.cpp
cfe/trunk/test/SemaCXX/unreachable-code.cpp
Modified: cfe/trunk/lib/Analysis/ReachableCode.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/ReachableCode.cpp?rev=354102&r1=354101&r2=354102&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/ReachableCode.cpp (original)
+++ cfe/trunk/lib/Analysis/ReachableCode.cpp Thu Feb 14 23:16:11 2019
@@ -631,6 +631,10 @@ void DeadCodeScan::reportDeadCode(const
// 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<CXXForRangeStmt>(LoopTarget))
+ return;
+
SourceLocation Loc = LoopTarget->getBeginLoc();
SourceRange R1(Loc, Loc), R2;
Modified: cfe/trunk/test/SemaCXX/unreachable-code.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/unreachable-code.cpp?rev=354102&r1=354101&r2=354102&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/unreachable-code.cpp (original)
+++ cfe/trunk/test/SemaCXX/unreachable-code.cpp Thu Feb 14 23:16:11 2019
@@ -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 {
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