[PATCH] D28278: [StaticAnalyzer] dont show wrong 'garbage value' warning when there is array index out of bounds

[Daniel Marjamäki via Phabricator via cfe-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL296326: [analyzer] clarify 'result is garbage value' when it is out of bounds (authored by danielmarjamaki).

Changed prior to commit:
  https://reviews.llvm.org/D28278?vs=89641&id=89854#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D28278

Files:
  cfe/trunk/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp
  cfe/trunk/test/Analysis/uninit-vals-ps.c


Index: cfe/trunk/test/Analysis/uninit-vals-ps.c
===================================================================
--- cfe/trunk/test/Analysis/uninit-vals-ps.c
+++ cfe/trunk/test/Analysis/uninit-vals-ps.c
@@ -57,6 +57,12 @@
   return s.x; // no-warning
 }
 
+void f6(int x) {
+  int a[20];
+  if (x == 25) {}
+  if (a[x] == 123) {} // expected-warning{{The left operand of '==' is a garbage value due to array index out of bounds}}
+}
+
 int ret_uninit() {
   int i;
   int *p = &i;
Index: cfe/trunk/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp
===================================================================
--- cfe/trunk/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp
+++ cfe/trunk/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp
@@ -35,6 +35,30 @@
 };
 } // end anonymous namespace
 
+static bool isArrayIndexOutOfBounds(CheckerContext &C, const Expr *Ex) {
+  ProgramStateRef state = C.getState();
+  const LocationContext *LCtx = C.getLocationContext();
+
+  if (!isa<ArraySubscriptExpr>(Ex))
+    return false;
+
+  SVal Loc = state->getSVal(Ex, LCtx);
+  if (!Loc.isValid())
+    return false;
+
+  const MemRegion *MR = Loc.castAs<loc::MemRegionVal>().getRegion();
+  const ElementRegion *ER = dyn_cast<ElementRegion>(MR);
+  if (!ER)
+    return false;
+
+  DefinedOrUnknownSVal Idx = ER->getIndex().castAs<DefinedOrUnknownSVal>();
+  DefinedOrUnknownSVal NumElements = C.getStoreManager().getSizeInElements(
+      state, ER->getSuperRegion(), ER->getValueType());
+  ProgramStateRef StInBound = state->assumeInBound(Idx, NumElements, true);
+  ProgramStateRef StOutBound = state->assumeInBound(Idx, NumElements, false);
+  return StOutBound && !StInBound;
+}
+
 void UndefResultChecker::checkPostStmt(const BinaryOperator *B,
                                        CheckerContext &C) const {
   ProgramStateRef state = C.getState();
@@ -77,6 +101,8 @@
          << " operand of '"
          << BinaryOperator::getOpcodeStr(B->getOpcode())
          << "' is a garbage value";
+      if (isArrayIndexOutOfBounds(C, Ex))
+        OS << " due to array index out of bounds";
     }
     else {
       // Neither operand was undefined, but the result is undefined.


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