1 files changed, 140 insertions, 0 deletions
diff --git a/lib/StaticAnalyzer/Checkers/NonnullGlobalConstantsChecker.cpp b/lib/StaticAnalyzer/Checkers/NonnullGlobalConstantsChecker.cpp
new file mode 100644
index 000000000000..0b4ecb41d20f
--- /dev/null
+++ b/lib/StaticAnalyzer/Checkers/NonnullGlobalConstantsChecker.cpp
@@ -0,0 +1,140 @@
+//==- NonnullGlobalConstantsChecker.cpp ---------------------------*- C++ -*--//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This checker adds an assumption that constant globals of certain types* are
+//  non-null, as otherwise they generally do not convey any useful information.
+//  The assumption is useful, as many framework use e. g. global const strings,
+//  and the analyzer might not be able to infer the global value if the
+//  definition is in a separate translation unit.
+//  The following types (and their typedef aliases) are considered to be
+//  non-null:
+//   - `char* const`
+//   - `const CFStringRef` from CoreFoundation
+//   - `NSString* const` from Foundation
+//   - `CFBooleanRef` from Foundation
+//
+//===----------------------------------------------------------------------===//
+
+#include "ClangSACheckers.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/CheckerContext.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+
+class NonnullGlobalConstantsChecker : public Checker<check::Location> {
+  mutable IdentifierInfo *NSStringII = nullptr;
+  mutable IdentifierInfo *CFStringRefII = nullptr;
+  mutable IdentifierInfo *CFBooleanRefII = nullptr;
+
+public:
+  NonnullGlobalConstantsChecker() {}
+
+  void checkLocation(SVal l, bool isLoad, const Stmt *S,
+                     CheckerContext &C) const;
+
+private:
+  void initIdentifierInfo(ASTContext &Ctx) const;
+
+  bool isGlobalConstString(SVal V) const;
+
+  bool isNonnullType(QualType Ty) const;
+};
+
+} // namespace
+
+/// Lazily initialize cache for required identifier informations.
+void NonnullGlobalConstantsChecker::initIdentifierInfo(ASTContext &Ctx) const {
+  if (NSStringII)
+    return;
+
+  NSStringII = &Ctx.Idents.get("NSString");
+  CFStringRefII = &Ctx.Idents.get("CFStringRef");
+  CFBooleanRefII = &Ctx.Idents.get("CFBooleanRef");
+}
+
+/// Add an assumption that const string-like globals are non-null.
+void NonnullGlobalConstantsChecker::checkLocation(SVal location, bool isLoad,
+                                                 const Stmt *S,
+                                                 CheckerContext &C) const {
+  initIdentifierInfo(C.getASTContext());
+  if (!isLoad || !location.isValid())
+    return;
+
+  ProgramStateRef State = C.getState();
+  SVal V = State->getSVal(location.castAs<Loc>());
+
+  if (isGlobalConstString(location)) {
+    Optional<DefinedOrUnknownSVal> Constr = V.getAs<DefinedOrUnknownSVal>();
+
+    if (Constr) {
+
+      // Assume that the variable is non-null.
+      ProgramStateRef OutputState = State->assume(*Constr, true);
+      C.addTransition(OutputState);
+    }
+  }
+}
+
+/// \param V loaded lvalue.
+/// \return whether {@code val} is a string-like const global.
+bool NonnullGlobalConstantsChecker::isGlobalConstString(SVal V) const {
+  Optional<loc::MemRegionVal> RegionVal = V.getAs<loc::MemRegionVal>();
+  if (!RegionVal)
+    return false;
+  auto *Region = dyn_cast<VarRegion>(RegionVal->getAsRegion());
+  if (!Region)
+    return false;
+  const VarDecl *Decl = Region->getDecl();
+
+  if (!Decl->hasGlobalStorage())
+    return false;
+
+  QualType Ty = Decl->getType();
+  bool HasConst = Ty.isConstQualified();
+  if (isNonnullType(Ty) && HasConst)
+    return true;
+
+  // Look through the typedefs.
+  while (auto *T = dyn_cast<TypedefType>(Ty)) {
+    Ty = T->getDecl()->getUnderlyingType();
+
+    // It is sufficient for any intermediate typedef
+    // to be classified const.
+    HasConst = HasConst || Ty.isConstQualified();
+    if (isNonnullType(Ty) && HasConst)
+      return true;
+  }
+  return false;
+}
+
+/// \return whether {@code type} is extremely unlikely to be null
+bool NonnullGlobalConstantsChecker::isNonnullType(QualType Ty) const {
+
+  if (Ty->isPointerType() && Ty->getPointeeType()->isCharType())
+    return true;
+
+  if (auto *T = dyn_cast<ObjCObjectPointerType>(Ty)) {
+    return T->getInterfaceDecl() &&
+      T->getInterfaceDecl()->getIdentifier() == NSStringII;
+  } else if (auto *T = dyn_cast<TypedefType>(Ty)) {
+    IdentifierInfo* II = T->getDecl()->getIdentifier();
+    return II == CFStringRefII || II == CFBooleanRefII;
+  }
+  return false;
+}
+
+void ento::registerNonnullGlobalConstantsChecker(CheckerManager &Mgr) {
+  Mgr.registerChecker<NonnullGlobalConstantsChecker>();
+}