From 25c1d57fc906e895535fb5c7e6dde80219f353b5 Mon Sep 17 00:00:00 2001
From: Ted Kremenek <kremenek@apple.com>
Date: Thu, 13 Sep 2012 00:21:35 +0000
Subject: [PATCH] Teach -Wuninitialized to recognize common "noreturn" idioms
 in Objective-C related to NSException.

Fixes <rdar://problem/12287498>

I debated whether or not this logic should be sunk into the CFG
itself.  It's not clear if we should, as different analyses may
wish to have different policies.  We can re-evaluate this in the
future.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@163760 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/UninitializedValues.cpp | 20 +++++++++++++++----
 test/SemaObjC/uninit-variables.m     | 29 ++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/lib/Analysis/UninitializedValues.cpp b/lib/Analysis/UninitializedValues.cpp
index 47f2cf67c8..8ebee9614a 100644
--- a/lib/Analysis/UninitializedValues.cpp
+++ b/lib/Analysis/UninitializedValues.cpp
@@ -22,6 +22,7 @@
 #include "clang/Analysis/AnalysisContext.h"
 #include "clang/Analysis/Visitors/CFGRecStmtDeclVisitor.h"
 #include "clang/Analysis/Analyses/UninitializedValues.h"
+#include "clang/Analysis/DomainSpecific/ObjCNoReturn.h"
 #include "llvm/Support/SaveAndRestore.h"
 
 using namespace clang;
@@ -412,6 +413,7 @@ class TransferFunctions : public StmtVisitor<TransferFunctions> {
   const CFGBlock *block;
   AnalysisDeclContext &ac;
   const ClassifyRefs &classification;
+  ObjCNoReturn objCNoRet;
   UninitVariablesHandler *handler;
 
 public:
@@ -420,16 +422,18 @@ public:
                     const ClassifyRefs &classification,
                     UninitVariablesHandler *handler)
     : vals(vals), cfg(cfg), block(block), ac(ac),
-      classification(classification), handler(handler) {}
+      classification(classification), objCNoRet(ac.getASTContext()),
+      handler(handler) {}
 
   void reportUse(const Expr *ex, const VarDecl *vd);
 
-  void VisitObjCForCollectionStmt(ObjCForCollectionStmt *FS);
+  void VisitBinaryOperator(BinaryOperator *bo);
   void VisitBlockExpr(BlockExpr *be);
   void VisitCallExpr(CallExpr *ce);
-  void VisitDeclStmt(DeclStmt *ds);
   void VisitDeclRefExpr(DeclRefExpr *dr);
-  void VisitBinaryOperator(BinaryOperator *bo);
+  void VisitDeclStmt(DeclStmt *ds);
+  void VisitObjCForCollectionStmt(ObjCForCollectionStmt *FS);
+  void VisitObjCMessageExpr(ObjCMessageExpr *ME);
 
   bool isTrackedVar(const VarDecl *vd) {
     return ::isTrackedVar(vd, cast<DeclContext>(ac.getDecl()));
@@ -689,6 +693,14 @@ void TransferFunctions::VisitDeclStmt(DeclStmt *DS) {
   }
 }
 
+void TransferFunctions::VisitObjCMessageExpr(ObjCMessageExpr *ME) {
+  // If the Objective-C message expression is an implicit no-return that
+  // is not modeled in the CFG, set the tracked dataflow values to Unknown.
+  if (objCNoRet.isImplicitNoReturn(ME)) {
+    vals.setAllScratchValues(Unknown);
+  }
+}
+
 //------------------------------------------------------------------------====//
 // High-level "driver" logic for uninitialized values analysis.
 //====------------------------------------------------------------------------//
diff --git a/test/SemaObjC/uninit-variables.m b/test/SemaObjC/uninit-variables.m
index cad0f54b2d..a3312264f0 100644
--- a/test/SemaObjC/uninit-variables.m
+++ b/test/SemaObjC/uninit-variables.m
@@ -1,5 +1,16 @@
 // RUN: %clang_cc1 -fsyntax-only -Wuninitialized -fsyntax-only -fblocks %s -verify
 
+#include <stdarg.h>
+
+@interface NSObject {} @end
+@class NSString;
+
+@interface NSException
++ (void)raise:(NSString *)name format:(NSString *)format, ...;
++ (void)raise:(NSString *)name format:(NSString *)format arguments:(va_list)argList;
+- (void)raise;
+@end
+
 // Duplicated from uninit-variables.c.
 // Test just to ensure the analysis is working.
 int test1() {
@@ -25,3 +36,21 @@ void test3() {
   }
 }
 
+int test_abort_on_exceptions(int y, NSException *e, NSString *s, int *z, ...) {
+  int x; // expected-note {{initialize the variable 'x' to silence this warning}}
+  if (y == 1) {
+    va_list alist;
+    va_start(alist, z);
+    [NSException raise:@"Blah" format:@"Blah %@" arguments:alist];
+    return x;
+  }
+  else if (y == 2) {
+	[NSException raise:@"Blah" format:s];
+	return x;  
+  }
+  else if (y == 3) {
+	[e raise];
+	return x;
+  }
+  return x; // expected-warning {{variable 'x' is uninitialized when used here}}
+}
-- 
2.40.0