george.karpenkov updated this revision to Diff 118522.
george.karpenkov added a comment.
Typo fix.
https://reviews.llvm.org/D38764
Files:
include/clang/StaticAnalyzer/Checkers/Checkers.td
lib/StaticAnalyzer/Checkers/CMakeLists.txt
lib/StaticAnalyzer/Checkers/NonnullStringConstantsChecker.cpp
test/Analysis/nonnull-string-constants.mm
Index: test/Analysis/nonnull-string-constants.mm
===================================================================
--- /dev/null
+++ test/Analysis/nonnull-string-constants.mm
@@ -0,0 +1,91 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify %s
+
+// Nullability of const string-like globals.
+// Relies on the checker defined in
+// lib/StaticAnalyzer/Checkers/NonnullStringConstantsChecker.cpp.
+
+void clang_analyzer_eval(bool);
+
+@class NSString;
+typedef const struct __CFString *CFStringRef;
+
+// Global NSString* is non-null.
+extern NSString *const StringConstGlobal;
+void stringConstGlobal() {
+ clang_analyzer_eval(StringConstGlobal); // expected-warning{{TRUE}}
+}
+
+// The logic does not apply to local variables though.
+extern NSString *stringGetter();
+void stringConstLocal() {
+ NSString *const local = stringGetter();
+ clang_analyzer_eval(local); // expected-warning{{UNKNOWN}}
+}
+
+// Global const CFStringRef's are also assumed to be non-null.
+extern const CFStringRef CFStringConstGlobal;
+void cfStringCheckGlobal() {
+ clang_analyzer_eval(CFStringConstGlobal); // expected-warning{{TRUE}}
+}
+
+// But only "const" ones.
+extern CFStringRef CFStringNonConstGlobal;
+void cfStringCheckMutableGlobal() {
+ clang_analyzer_eval(CFStringNonConstGlobal); // expected-warning{{UNKNOWN}}
+}
+
+// char* const is also assumed to be non-null.
+extern const char *const ConstCharStarConst;
+void constCharStarCheckGlobal() {
+ clang_analyzer_eval(ConstCharStarConst); // expected-warning{{TRUE}}
+}
+
+// Pointer value can be mutable.
+extern char *const CharStarConst;
+void charStarCheckGlobal() {
+ clang_analyzer_eval(CharStarConst); // expected-warning{{TRUE}}
+}
+
+// But the pointer itself should be immutable.
+extern char *CharStar;
+void charStartCheckMutableGlobal() {
+ clang_analyzer_eval(CharStar); // expected-warning{{UNKNOWN}}
+}
+
+// Type definitions should also work across typedefs, for pointers:
+typedef char *const str;
+extern str globalStr;
+void charStarCheckTypedef() {
+ clang_analyzer_eval(globalStr); // expected-warning{{TRUE}}
+}
+
+// And for types.
+typedef NSString *const NStr;
+extern NStr globalNSString;
+void NSStringCheckTypedef() {
+ clang_analyzer_eval(globalNSString); // expected-warning{{TRUE}}
+}
+
+// Note that constness could be either inside
+// the var declaration, or in a typedef.
+typedef NSString *NStr2;
+extern const NStr2 globalNSString2;
+void NSStringCheckConstTypedef() {
+ clang_analyzer_eval(globalNSString2); // expected-warning{{TRUE}}
+}
+
+// Nested typedefs should work as well.
+typedef const CFStringRef str1;
+typedef str1 str2;
+extern str2 globalStr2;
+void testNestedTypedefs() {
+ clang_analyzer_eval(globalStr2); // expected-warning{{TRUE}}
+}
+
+// And for NSString *.
+typedef NSString *const nstr1;
+typedef nstr1 nstr2;
+extern nstr2 nglobalStr2;
+void testNestedTypedefsForNSString() {
+ clang_analyzer_eval(nglobalStr2); // expected-warning{{TRUE}}
+}
Index: lib/StaticAnalyzer/Checkers/NonnullStringConstantsChecker.cpp
===================================================================
--- /dev/null
+++ lib/StaticAnalyzer/Checkers/NonnullStringConstantsChecker.cpp
@@ -0,0 +1,141 @@
+//==-- RetainCountChecker.cpp - Checks for leaks and other issues -*- C++ -*--//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Class definition for NonnullStringConstantsChecker.
+// This checker adds an assumption that constant string-like globals are
+// non-null, as otherwise they generally do not convey any useful information.
+// The assumption is useful, as many framework use such 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 string-like:
+// - `char* const`
+// - `const CFStringRef` from CoreFoundation
+// - `NSString* const` from Foundation
+//
+// Checker uses are defined in the test file:
+// - test/Analysis/nonnull-string-constants.mm
+//
+//===----------------------------------------------------------------------===//
+
+//
+// This checker ensures that const string globals are assumed to be non-null.
+//
+#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 NonnullStringConstantsChecker : public Checker<check::Location> {
+ mutable IdentifierInfo *NSStringII = nullptr;
+ mutable IdentifierInfo *CFStringRefII = nullptr;
+
+public:
+ NonnullStringConstantsChecker() {}
+
+ /// Add an assumption that const string-like globals are non-null.
+ void checkLocation(SVal l, bool isLoad, const Stmt *S,
+ CheckerContext &C) const;
+
+private:
+ /// Lazily initialize cache for required identifier informations.
+ void initIdentifierInfo(ASTContext &Ctx) const;
+
+ /// \param val loaded lvalue.
+ /// \return whether {@code val} is a string-like const global.
+ bool isGlobalConstString(SVal val) const;
+
+ /// \return whether {@code type} is a string-like type.
+ bool isStringlike(QualType type) const;
+};
+
+} // namespace
+
+void NonnullStringConstantsChecker::initIdentifierInfo(ASTContext &Ctx) const {
+ if (NSStringII)
+ return;
+
+ NSStringII = &Ctx.Idents.get("NSString");
+ CFStringRefII = &Ctx.Idents.get("CFStringRef");
+}
+
+void NonnullStringConstantsChecker::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);
+ }
+ }
+}
+
+bool NonnullStringConstantsChecker::isGlobalConstString(SVal val) const {
+ Optional<loc::MemRegionVal> regionVal = val.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 type = decl->getType();
+ bool hasConst = type.isConstQualified();
+ if (isStringlike(type) && hasConst)
+ return true;
+
+ // Look through the typedefs.
+ while (const TypedefType *T = dyn_cast<TypedefType>(type)) {
+ type = T->getDecl()->getUnderlyingType();
+
+ // It is sufficient for any intermediate typedef
+ // to be classified const.
+ hasConst = hasConst || type.isConstQualified();
+ if (isStringlike(type) && hasConst)
+ return true;
+ }
+ return false;
+}
+
+bool NonnullStringConstantsChecker::isStringlike(QualType type) const {
+
+ if (type->isPointerType() && type->getPointeeType()->isCharType())
+ return true;
+
+ if (const ObjCObjectPointerType *T = dyn_cast<ObjCObjectPointerType>(type)) {
+ return T->getInterfaceDecl()->getIdentifier() == NSStringII;
+ } else if (const TypedefType *T = dyn_cast<TypedefType>(type)) {
+ return T->getDecl()->getIdentifier() == CFStringRefII;
+ }
+ return false;
+}
+
+void ento::registerNonnullStringConstantsChecker(CheckerManager &Mgr) {
+ Mgr.registerChecker<NonnullStringConstantsChecker>();
+}
Index: lib/StaticAnalyzer/Checkers/CMakeLists.txt
===================================================================
--- lib/StaticAnalyzer/Checkers/CMakeLists.txt
+++ lib/StaticAnalyzer/Checkers/CMakeLists.txt
@@ -57,6 +57,7 @@
NSErrorChecker.cpp
NoReturnFunctionChecker.cpp
NonNullParamChecker.cpp
+ NonnullStringConstantsChecker.cpp
NullabilityChecker.cpp
NumberObjectConversionChecker.cpp
ObjCAtSyncChecker.cpp
Index: include/clang/StaticAnalyzer/Checkers/Checkers.td
===================================================================
--- include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -132,6 +132,10 @@
HelpText<"Generate dynamic type information">,
DescFile<"DynamicTypePropagation.cpp">;
+def NonnullStringConstantsChecker: Checker<"NonnilStringConstants">,
+ HelpText<"Assume that const string-like globals are non-null">,
+ DescFile<"NonilStringConstantsChecker.cpp">;
+
} // end "core"
let ParentPackage = CoreAlpha in {
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