[-Wunreachable-code] add a specialized diagnostic for unreachable increment expressions of loops.

llvm-svn: 204430

1 files changed, 20 insertions, 0 deletions

diff --git a/clang/lib/Analysis/ReachableCode.cpp b/clang/lib/Analysis/ReachableCode.cpp
index 4220000..53e03de 100644
--- a/clang/lib/Analysis/ReachableCode.cpp
+++ b/clang/lib/Analysis/ReachableCode.cpp
@@ -529,6 +529,26 @@ void DeadCodeScan::reportDeadCode(const CFGBlock *B,
     UK = reachable_code::UK_Return;
   }
 
+  if (UK == reachable_code::UK_Other) {
+    // Check if the dead code is part of the "loop target" of
+    // a for/for-range loop.  This is the block that contains
+    // the increment code.
+    if (const Stmt *LoopTarget = B->getLoopTarget()) {
+      SourceLocation Loc = LoopTarget->getLocStart();
+      SourceRange R1(Loc, Loc), R2;
+
+      if (const ForStmt *FS = dyn_cast<ForStmt>(LoopTarget)) {
+        const Expr *Inc = FS->getInc();
+        Loc = Inc->getLocStart();
+        R2 = Inc->getSourceRange();
+      }
+
+      CB.HandleUnreachable(reachable_code::UK_Loop_Increment,
+                           Loc, SourceRange(Loc, Loc), R2);
+      return;
+    }
+  }
+
   SourceRange R1, R2;
   SourceLocation Loc = GetUnreachableLoc(S, R1, R2);
   CB.HandleUnreachable(UK, Loc, R1, R2);