1 files changed, 231 insertions, 0 deletions
diff --git a/clang/lib/StaticAnalyzer/Checkers/NonNullParamChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/NonNullParamChecker.cpp
new file mode 100644
index 000000000000..6ffc89745365
--- /dev/null
+++ b/clang/lib/StaticAnalyzer/Checkers/NonNullParamChecker.cpp
@@ -0,0 +1,231 @@
+//===--- NonNullParamChecker.cpp - Undefined arguments checker -*- C++ -*--===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This defines NonNullParamChecker, which checks for arguments expected not to
+// be null due to:
+//   - the corresponding parameters being declared to have nonnull attribute
+//   - the corresponding parameters being references; since the call would form
+//     a reference to a null pointer
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/AST/Attr.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class NonNullParamChecker
+  : public Checker< check::PreCall, EventDispatcher<ImplicitNullDerefEvent> > {
+  mutable std::unique_ptr<BugType> BTAttrNonNull;
+  mutable std::unique_ptr<BugType> BTNullRefArg;
+
+public:
+
+  void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
+
+  std::unique_ptr<PathSensitiveBugReport>
+  genReportNullAttrNonNull(const ExplodedNode *ErrorN,
+                           const Expr *ArgE,
+                           unsigned IdxOfArg) const;
+  std::unique_ptr<PathSensitiveBugReport>
+  genReportReferenceToNullPointer(const ExplodedNode *ErrorN,
+                                  const Expr *ArgE) const;
+};
+} // end anonymous namespace
+
+/// \return Bitvector marking non-null attributes.
+static llvm::SmallBitVector getNonNullAttrs(const CallEvent &Call) {
+  const Decl *FD = Call.getDecl();
+  unsigned NumArgs = Call.getNumArgs();
+  llvm::SmallBitVector AttrNonNull(NumArgs);
+  for (const auto *NonNull : FD->specific_attrs<NonNullAttr>()) {
+    if (!NonNull->args_size()) {
+      AttrNonNull.set(0, NumArgs);
+      break;
+    }
+    for (const ParamIdx &Idx : NonNull->args()) {
+      unsigned IdxAST = Idx.getASTIndex();
+      if (IdxAST >= NumArgs)
+        continue;
+      AttrNonNull.set(IdxAST);
+    }
+  }
+  return AttrNonNull;
+}
+
+void NonNullParamChecker::checkPreCall(const CallEvent &Call,
+                                       CheckerContext &C) const {
+  if (!Call.getDecl())
+    return;
+
+  llvm::SmallBitVector AttrNonNull = getNonNullAttrs(Call);
+  unsigned NumArgs = Call.getNumArgs();
+
+  ProgramStateRef state = C.getState();
+  ArrayRef<ParmVarDecl*> parms = Call.parameters();
+
+  for (unsigned idx = 0; idx < NumArgs; ++idx) {
+    // For vararg functions, a corresponding parameter decl may not exist.
+    bool HasParam = idx < parms.size();
+
+    // Check if the parameter is a reference. We want to report when reference
+    // to a null pointer is passed as a parameter.
+    bool haveRefTypeParam =
+        HasParam ? parms[idx]->getType()->isReferenceType() : false;
+    bool haveAttrNonNull = AttrNonNull[idx];
+
+    // Check if the parameter is also marked 'nonnull'.
+    if (!haveAttrNonNull && HasParam)
+      haveAttrNonNull = parms[idx]->hasAttr<NonNullAttr>();
+
+    if (!haveAttrNonNull && !haveRefTypeParam)
+      continue;
+
+    // If the value is unknown or undefined, we can't perform this check.
+    const Expr *ArgE = Call.getArgExpr(idx);
+    SVal V = Call.getArgSVal(idx);
+    auto DV = V.getAs<DefinedSVal>();
+    if (!DV)
+      continue;
+
+    assert(!haveRefTypeParam || DV->getAs<Loc>());
+
+    // Process the case when the argument is not a location.
+    if (haveAttrNonNull && !DV->getAs<Loc>()) {
+      // If the argument is a union type, we want to handle a potential
+      // transparent_union GCC extension.
+      if (!ArgE)
+        continue;
+
+      QualType T = ArgE->getType();
+      const RecordType *UT = T->getAsUnionType();
+      if (!UT || !UT->getDecl()->hasAttr<TransparentUnionAttr>())
+        continue;
+
+      auto CSV = DV->getAs<nonloc::CompoundVal>();
+
+      // FIXME: Handle LazyCompoundVals?
+      if (!CSV)
+        continue;
+
+      V = *(CSV->begin());
+      DV = V.getAs<DefinedSVal>();
+      assert(++CSV->begin() == CSV->end());
+      // FIXME: Handle (some_union){ some_other_union_val }, which turns into
+      // a LazyCompoundVal inside a CompoundVal.
+      if (!V.getAs<Loc>())
+        continue;
+
+      // Retrieve the corresponding expression.
+      if (const auto *CE = dyn_cast<CompoundLiteralExpr>(ArgE))
+        if (const auto *IE = dyn_cast<InitListExpr>(CE->getInitializer()))
+          ArgE = dyn_cast<Expr>(*(IE->begin()));
+    }
+
+    ConstraintManager &CM = C.getConstraintManager();
+    ProgramStateRef stateNotNull, stateNull;
+    std::tie(stateNotNull, stateNull) = CM.assumeDual(state, *DV);
+
+    // Generate an error node.  Check for a null node in case
+    // we cache out.
+    if (stateNull && !stateNotNull) {
+      if (ExplodedNode *errorNode = C.generateErrorNode(stateNull)) {
+
+        std::unique_ptr<BugReport> R;
+        if (haveAttrNonNull)
+          R = genReportNullAttrNonNull(errorNode, ArgE, idx + 1);
+        else if (haveRefTypeParam)
+          R = genReportReferenceToNullPointer(errorNode, ArgE);
+
+        // Highlight the range of the argument that was null.
+        R->addRange(Call.getArgSourceRange(idx));
+
+        // Emit the bug report.
+        C.emitReport(std::move(R));
+      }
+
+      // Always return.  Either we cached out or we just emitted an error.
+      return;
+    }
+
+    if (stateNull) {
+      if (ExplodedNode *N = C.generateSink(stateNull, C.getPredecessor())) {
+        ImplicitNullDerefEvent event = {
+          V, false, N, &C.getBugReporter(),
+          /*IsDirectDereference=*/haveRefTypeParam};
+        dispatchEvent(event);
+      }
+    }
+
+    // If a pointer value passed the check we should assume that it is
+    // indeed not null from this point forward.
+    state = stateNotNull;
+  }
+
+  // If we reach here all of the arguments passed the nonnull check.
+  // If 'state' has been updated generated a new node.
+  C.addTransition(state);
+}
+
+std::unique_ptr<PathSensitiveBugReport>
+NonNullParamChecker::genReportNullAttrNonNull(const ExplodedNode *ErrorNode,
+                                              const Expr *ArgE,
+                                              unsigned IdxOfArg) const {
+  // Lazily allocate the BugType object if it hasn't already been
+  // created. Ownership is transferred to the BugReporter object once
+  // the BugReport is passed to 'EmitWarning'.
+  if (!BTAttrNonNull)
+    BTAttrNonNull.reset(new BugType(
+        this, "Argument with 'nonnull' attribute passed null", "API"));
+
+  llvm::SmallString<256> SBuf;
+  llvm::raw_svector_ostream OS(SBuf);
+  OS << "Null pointer passed to "
+     << IdxOfArg << llvm::getOrdinalSuffix(IdxOfArg)
+     << " parameter expecting 'nonnull'";
+
+  auto R =
+      std::make_unique<PathSensitiveBugReport>(*BTAttrNonNull, SBuf, ErrorNode);
+  if (ArgE)
+    bugreporter::trackExpressionValue(ErrorNode, ArgE, *R);
+
+  return R;
+}
+
+std::unique_ptr<PathSensitiveBugReport>
+NonNullParamChecker::genReportReferenceToNullPointer(
+    const ExplodedNode *ErrorNode, const Expr *ArgE) const {
+  if (!BTNullRefArg)
+    BTNullRefArg.reset(new BuiltinBug(this, "Dereference of null pointer"));
+
+  auto R = std::make_unique<PathSensitiveBugReport>(
+      *BTNullRefArg, "Forming reference to null pointer", ErrorNode);
+  if (ArgE) {
+    const Expr *ArgEDeref = bugreporter::getDerefExpr(ArgE);
+    if (!ArgEDeref)
+      ArgEDeref = ArgE;
+    bugreporter::trackExpressionValue(ErrorNode, ArgEDeref, *R);
+  }
+  return R;
+
+}
+
+void ento::registerNonNullParamChecker(CheckerManager &mgr) {
+  mgr.registerChecker<NonNullParamChecker>();
+}
+
+bool ento::shouldRegisterNonNullParamChecker(const LangOptions &LO) {
+  return true;
+}