From: Ted Kremenek <kremenek@apple.com>
Date: Thu, 22 Mar 2012 05:57:43 +0000 (+0000)
Subject: Fix broken CFG when an initializer is a statement expression that starts with a while... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=550f2234fc9218914c325041067052342dfce553;p=clang

Fix broken CFG when an initializer is a statement expression that starts with a while loop (PR 12325).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153242 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/CFG.cpp b/lib/Analysis/CFG.cpp
index 24ca958827..d0ccef6890 100644
--- a/lib/Analysis/CFG.cpp
+++ b/lib/Analysis/CFG.cpp
@@ -1464,14 +1464,24 @@ CFGBlock *CFGBuilder::VisitDeclSubExpr(DeclStmt *DS) {
 
   autoCreateBlock();
   appendStmt(Block, DS);
+  
+  // Keep track of the last non-null block, as 'Block' can be nulled out
+  // if the initializer expression is something like a 'while' in a
+  // statement-expression.
+  CFGBlock *LastBlock = Block;
 
   if (Init) {
-    if (HasTemporaries)
+    if (HasTemporaries) {
       // For expression with temporaries go directly to subexpression to omit
       // generating destructors for the second time.
-      Visit(cast<ExprWithCleanups>(Init)->getSubExpr());
-    else
-      Visit(Init);
+      ExprWithCleanups *EC = cast<ExprWithCleanups>(Init);
+      if (CFGBlock *newBlock = Visit(EC->getSubExpr()))
+        LastBlock = newBlock;
+    }
+    else {
+      if (CFGBlock *newBlock = Visit(Init))
+        LastBlock = newBlock;
+    }
   }
 
   // If the type of VD is a VLA, then we must process its size expressions.
@@ -1483,7 +1493,7 @@ CFGBlock *CFGBuilder::VisitDeclSubExpr(DeclStmt *DS) {
   if (ScopePos && VD == *ScopePos)
     ++ScopePos;
 
-  return Block;
+  return Block ? Block : LastBlock;
 }
 
 CFGBlock *CFGBuilder::VisitIfStmt(IfStmt *I) {
diff --git a/test/SemaCXX/uninitialized.cpp b/test/SemaCXX/uninitialized.cpp
index 9550682918..15c06eb421 100644
--- a/test/SemaCXX/uninitialized.cpp
+++ b/test/SemaCXX/uninitialized.cpp
@@ -147,3 +147,18 @@ namespace rdar10398199 {
     (void)y;
   };
 }
+
+// PR 12325 - this was a false uninitialized value warning due to
+// a broken CFG.
+int pr12325(int params) {
+  int x = ({
+    while (false)
+      ;
+    int _v = params;
+    if (false)
+      ;
+    _v; // no-warning
+  });
+  return x;
+}
+