[PATCH] D32291: [analyzer] Implement handling array subscript into null pointer, improve null dereference checks for array subscripts

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This revision was automatically updated to reflect the committed changes.
Closed by commit rL301251: [analyzer] Improve subscripting null arrays for catching null dereferences. (authored by dergachev).

Changed prior to commit:
  https://reviews.llvm.org/D32291?vs=95943&id=96468#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D32291

Files:
  cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
  cfe/trunk/lib/StaticAnalyzer/Core/RegionStore.cpp
  cfe/trunk/test/Analysis/null-deref-offsets.c


Index: cfe/trunk/test/Analysis/null-deref-offsets.c
===================================================================
--- cfe/trunk/test/Analysis/null-deref-offsets.c
+++ cfe/trunk/test/Analysis/null-deref-offsets.c
@@ -7,7 +7,7 @@
   int z[2];
 };
 
-void testOffsets(struct S *s) {
+void testOffsets(struct S *s, int coin) {
   if (s != 0)
     return;
 
@@ -21,14 +21,17 @@
 
   // FIXME: These should ideally be true.
   clang_analyzer_eval(&(s->y) == 4); // expected-warning{{FALSE}}
-  clang_analyzer_eval(&(s->z[0]) == 8); // expected-warning{{UNKNOWN}}
-  clang_analyzer_eval(&(s->z[1]) == 12); // expected-warning{{UNKNOWN}}
+  clang_analyzer_eval(&(s->z[0]) == 8); // expected-warning{{FALSE}}
+  clang_analyzer_eval(&(s->z[1]) == 12); // expected-warning{{FALSE}}
 
   // FIXME: These should ideally be false.
   clang_analyzer_eval(&(s->y) == 0); // expected-warning{{TRUE}}
-  clang_analyzer_eval(&(s->z[0]) == 0); // expected-warning{{UNKNOWN}}
-  clang_analyzer_eval(&(s->z[1]) == 0); // expected-warning{{UNKNOWN}}
+  clang_analyzer_eval(&(s->z[0]) == 0); // expected-warning{{TRUE}}
+  clang_analyzer_eval(&(s->z[1]) == 0); // expected-warning{{TRUE}}
 
-  // But this should still be a null dereference.
-  s->y = 5; // expected-warning{{Access to field 'y' results in a dereference of a null pointer (loaded from variable 's')}}
+  // But these should still be reported as null dereferences.
+  if (coin)
+    s->y = 5; // expected-warning{{Access to field 'y' results in a dereference of a null pointer (loaded from variable 's')}}
+  else
+    s->z[1] = 6; // expected-warning{{Array access (via field 'z') results in a null pointer dereference}}
 }
Index: cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
===================================================================
--- cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
+++ cfe/trunk/lib/StaticAnalyzer/Core/BugReporterVisitors.cpp
@@ -61,7 +61,9 @@
         return U->getSubExpr()->IgnoreParenCasts();
     }
     else if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
-      if (ME->isArrow() || isDeclRefExprToReference(ME->getBase())) {
+      if (ME->isImplicitAccess()) {
+        return ME;
+      } else if (ME->isArrow() || isDeclRefExprToReference(ME->getBase())) {
         return ME->getBase()->IgnoreParenCasts();
       } else {
         // If we have a member expr with a dot, the base must have been
@@ -73,9 +75,9 @@
       return IvarRef->getBase()->IgnoreParenCasts();
     }
     else if (const ArraySubscriptExpr *AE = dyn_cast<ArraySubscriptExpr>(E)) {
-      return AE->getBase();
+      return getDerefExpr(AE->getBase());
     }
-    else if (isDeclRefExprToReference(E)) {
+    else if (isa<DeclRefExpr>(E)) {
       return E;
     }
     break;
@@ -974,14 +976,11 @@
     // This code interacts heavily with this hack; otherwise the value
     // would not be null at all for most fields, so we'd be unable to track it.
     if (const auto *Op = dyn_cast<UnaryOperator>(Ex))
-      if (Op->getOpcode() == UO_AddrOf && Op->getSubExpr()->isLValue()) {
-        Ex = Op->getSubExpr()->IgnoreParenCasts();
-        while (const auto *ME = dyn_cast<MemberExpr>(Ex)) {
-          Ex = ME->getBase()->IgnoreParenCasts();
-        }
-      }
+      if (Op->getOpcode() == UO_AddrOf && Op->getSubExpr()->isLValue())
+        if (const Expr *DerefEx = getDerefExpr(Op->getSubExpr()))
+          Ex = DerefEx;
 
-    if (ExplodedGraph::isInterestingLValueExpr(Ex) || CallEvent::isCallStmt(Ex))
+    if (Ex && (ExplodedGraph::isInterestingLValueExpr(Ex) || CallEvent::isCallStmt(Ex)))
       Inner = Ex;
   }
 
Index: cfe/trunk/lib/StaticAnalyzer/Core/RegionStore.cpp
===================================================================
--- cfe/trunk/lib/StaticAnalyzer/Core/RegionStore.cpp
+++ cfe/trunk/lib/StaticAnalyzer/Core/RegionStore.cpp
@@ -1338,6 +1338,9 @@
 ///  the array).  This is called by ExprEngine when evaluating casts
 ///  from arrays to pointers.
 SVal RegionStoreManager::ArrayToPointer(Loc Array, QualType T) {
+  if (Array.getAs<loc::ConcreteInt>())
+    return Array;
+
   if (!Array.getAs<loc::MemRegionVal>())
     return UnknownVal();
 


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