[analyzer] Match more patterns in bugreporter::getDerefExpr() API.

This function can now track null pointer through simple pointer arithmetic, such as '*&*(p + 2)' => 'p' and so on, displaying intermediate diagnostic pieces for the user to understand where the null pointer is coming from. Differential Revision: https://reviews.llvm.org/D37025 llvm-svn: 314290
llvm · Sep 27, 2017 · 8c80061 · 8c80061
1 parent 92c21d5
commit 8c80061
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Showing 4 changed files with 80 additions and 21 deletions.
diff --git a/clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp b/clang/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
@@ -66,12 +66,24 @@ const Expr *bugreporter::getDerefExpr(const Stmt *S) {
         break;
       }
       E = CE->getSubExpr();
-    } else if (isa<BinaryOperator>(E)) {
-      // Probably more arithmetic can be pattern-matched here,
-      // but for now give up.
-      break;
+    } else if (const BinaryOperator *B = dyn_cast<BinaryOperator>(E)) {
+      // Pointer arithmetic: '*(x + 2)' -> 'x') etc.
+      if (B->getType()->isPointerType()) {
+        if (B->getLHS()->getType()->isPointerType()) {
+          E = B->getLHS();
+        } else if (B->getRHS()->getType()->isPointerType()) {
+          E = B->getRHS();
+        } else {
+          break;
+        }
+      } else {
+        // Probably more arithmetic can be pattern-matched here,
+        // but for now give up.
+        break;
+      }
     } else if (const UnaryOperator *U = dyn_cast<UnaryOperator>(E)) {
-      if (U->getOpcode() == UO_Deref) {
+      if (U->getOpcode() == UO_Deref || U->getOpcode() == UO_AddrOf ||
+          (U->isIncrementDecrementOp() && U->getType()->isPointerType())) {
         // Operators '*' and '&' don't actually mean anything.
         // We look at casts instead.
         E = U->getSubExpr();

diff --git a/clang/test/Analysis/inlining/inline-defensive-checks.c b/clang/test/Analysis/inlining/inline-defensive-checks.c
@@ -169,6 +169,18 @@ void idcTrackZeroValueThroughUnaryPointerOperatorsWithAssignment(struct S *s) {
   *x = 7; // no-warning
 }
 
+void idcTrackZeroValueThroughManyUnaryPointerOperatorsWithAssignment(struct S *s) {
+  idc(s);
+  int *x = &*&(s->f1);
+  *x = 7; // no-warning
+}
+
+void idcTrackZeroValueThroughManyUnaryPointerOperatorsWithAssignmentAndUnaryIncrement(struct S *s) {
+  idc(s);
+  int *x = &*&((++s)->f1);
+  *x = 7; // no-warning
+}
+
 
 struct S2 {
   int a[1];

diff --git a/clang/test/Analysis/null-deref-path-notes.c b/clang/test/Analysis/null-deref-path-notes.c
@@ -4,7 +4,7 @@
 // of the null pointer for path notes. Apparently, not much actual tracking
 // needs to be done in this example.
 void pr34373() {
-  int *a = 0;
+  int *a = 0; // expected-note{{'a' initialized to a null pointer value}}
   (a + 0)[0]; // expected-warning{{Array access results in a null pointer dereference}}
               // expected-note@-1{{Array access results in a null pointer dereference}}
 }
diff --git a/clang/test/Analysis/nullptr.cpp b/clang/test/Analysis/nullptr.cpp
@@ -1,11 +1,12 @@
-// RUN: %clang_analyze_cc1 -std=c++11 -Wno-conversion-null -analyzer-checker=core,debug.ExprInspection -analyzer-store region -verify %s
+// RUN: %clang_analyze_cc1 -std=c++11 -Wno-conversion-null -analyzer-checker=core,debug.ExprInspection -analyzer-store region -analyzer-output=text -verify %s
 
 void clang_analyzer_eval(int);
 
 // test to see if nullptr is detected as a null pointer
 void foo1(void) {
-  char  *np = nullptr;
+  char  *np = nullptr; // expected-note{{'np' initialized to a null pointer value}}
   *np = 0;  // expected-warning{{Dereference of null pointer}}
+            // expected-note@-1{{Dereference of null pointer}}
 }
 
 // check if comparing nullptr to nullptr is detected properly
@@ -23,10 +24,11 @@ void foo3(void) {
   struct foo {
     int a, f;
   };
-  char *np = nullptr;
+  char *np = nullptr; // expected-note{{'np' initialized to a null pointer value}}
   // casting a nullptr to anything should be caught eventually
-  int *ip = &(((struct foo *)np)->f);
+  int *ip = &(((struct foo *)np)->f); // expected-note{{'ip' initialized to a null pointer value}}
   *ip = 0;  // expected-warning{{Dereference of null pointer}}
+            // expected-note@-1{{Dereference of null pointer}}
   // should be error here too, but analysis gets stopped
 //  *np = 0;
 }
@@ -49,16 +51,31 @@ int pr10372(void *& x) {
 }
 
 void zoo1() {
-  char **p = 0;
+  char **p = 0; // expected-note{{'p' initialized to a null pointer value}}
   delete *(p + 0); // expected-warning{{Dereference of null pointer}}
+                   // expected-note@-1{{Dereference of null pointer}}
+}
+
+void zoo1backwards() {
+  char **p = 0; // expected-note{{'p' initialized to a null pointer value}}
+  delete *(0 + p); // expected-warning{{Dereference of null pointer}}
+                   // expected-note@-1{{Dereference of null pointer}}
+}
+
+typedef __INTPTR_TYPE__ intptr_t;
+void zoo1multiply() {
+  char **p = 0; // FIXME-should-be-note:{{'p' initialized to a null pointer value}}
+  delete *((char **)((intptr_t)p * 2)); // expected-warning{{Dereference of null pointer}}
+                   // expected-note@-1{{Dereference of null pointer}}
 }
 
 void zoo2() {
   int **a = 0;
-  int **b = 0;
+  int **b = 0; // expected-note{{'b' initialized to a null pointer value}}
   asm ("nop"
       :"=r"(*a)
       :"0"(*b) // expected-warning{{Dereference of null pointer}}
+               // expected-note@-1{{Dereference of null pointer}}
       );
 }
 
@@ -70,17 +87,19 @@ int exprWithCleanups() {
     int a;
   };
 
-  int *x = 0;
+  int *x = 0; // expected-note{{'x' initialized to a null pointer value}}
   return S(*x).a; // expected-warning{{Dereference of null pointer}}
+                  // expected-note@-1{{Dereference of null pointer}}
 }
 
 int materializeTempExpr() {
-  int *n = 0;
+  int *n = 0; // expected-note{{'n' initialized to a null pointer value}}
   struct S {
     int a;
     S(int i): a(i) {}
   };
   const S &s = S(*n); // expected-warning{{Dereference of null pointer}}
+                      // expected-note@-1{{Dereference of null pointer}}
   return s.a;
 }
 
@@ -98,33 +117,49 @@ struct X {
 
 void invokeF(X* x) {
   x->f(); // expected-warning{{Called C++ object pointer is null}}
+          // expected-note@-1{{Called C++ object pointer is null}}
 }
 
 struct Type {
   decltype(nullptr) x;
 };
 
 void shouldNotCrash() {
-  decltype(nullptr) p;
-  if (getSymbol())
-    invokeF(p); // expected-warning{{1st function call argument is an uninit}}
-  if (getSymbol())
-    invokeF(nullptr);
-  if (getSymbol()) {
-    X *x = Type().x;
+  decltype(nullptr) p; // expected-note{{'p' declared without an initial value}}
+  if (getSymbol()) // expected-note   {{Assuming the condition is false}}
+                   // expected-note@-1{{Taking false branch}}
+                   // expected-note@-2{{Assuming the condition is false}}
+                   // expected-note@-3{{Taking false branch}}
+                   // expected-note@-4{{Assuming the condition is true}}
+                   // expected-note@-5{{Taking true branch}}
+    invokeF(p); // expected-warning{{1st function call argument is an uninitialized value}}
+                // expected-note@-1{{1st function call argument is an uninitialized value}}
+  if (getSymbol()) // expected-note   {{Assuming the condition is false}}
+                   // expected-note@-1{{Taking false branch}}
+                   // expected-note@-2{{Assuming the condition is true}}
+                   // expected-note@-3{{Taking true branch}}
+    invokeF(nullptr); // expected-note   {{Calling 'invokeF'}}
+                      // expected-note@-1{{Passing null pointer value via 1st parameter 'x'}}
+  if (getSymbol()) {  // expected-note  {{Assuming the condition is true}}
+                      // expected-note@-1{{Taking true branch}}
+    X *x = Type().x; // expected-note{{'x' initialized to a null pointer value}}
     x->f(); // expected-warning{{Called C++ object pointer is null}}
+            // expected-note@-1{{Called C++ object pointer is null}}
   }
 }
 
 void f(decltype(nullptr) p) {
   int *q = nullptr;
   clang_analyzer_eval(p == 0); // expected-warning{{TRUE}}
+                               // expected-note@-1{{TRUE}}
   clang_analyzer_eval(q == 0); // expected-warning{{TRUE}}
+                               // expected-note@-1{{TRUE}}
 }
 
 decltype(nullptr) returnsNullPtrType();
 void fromReturnType() {
   ((X *)returnsNullPtrType())->f(); // expected-warning{{Called C++ object pointer is null}}
+                                    // expected-note@-1{{Called C++ object pointer is null}}
 }
 
 #define AS_ATTRIBUTE __attribute__((address_space(256)))