[clang] [llvm] [FlowSensitive] [StatusOr] [2/N] Add minimal model (PR #162932)

[Yitzhak Mandelbaum via cfe-commits]

================
@@ -0,0 +1,284 @@
+//===- UncheckedStatusOrAccessModel.cpp -----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/FlowSensitive/Models/UncheckedStatusOrAccessModel.h"
+
+#include <cassert>
+#include <utility>
+
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclTemplate.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/AST/TypeBase.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersInternal.h"
+#include "clang/Analysis/CFG.h"
+#include "clang/Analysis/FlowSensitive/CFGMatchSwitch.h"
+#include "clang/Analysis/FlowSensitive/DataflowAnalysis.h"
+#include "clang/Analysis/FlowSensitive/DataflowEnvironment.h"
+#include "clang/Analysis/FlowSensitive/MatchSwitch.h"
+#include "clang/Analysis/FlowSensitive/StorageLocation.h"
+#include "clang/Analysis/FlowSensitive/Value.h"
+#include "clang/Basic/LLVM.h"
+#include "clang/Basic/SourceLocation.h"
+#include "llvm/ADT/StringMap.h"
+
+namespace clang::dataflow::statusor_model {
+namespace {
+
+using ::clang::ast_matchers::MatchFinder;
+using ::clang::ast_matchers::StatementMatcher;
+
+} // namespace
+
+static bool isStatusOrOperatorBaseType(QualType type) {
+  return isRecordTypeWithName(type, "absl::internal_statusor::OperatorBase");
+}
+
+static bool isSafeUnwrap(RecordStorageLocation *StatusOrLoc,
+                         const Environment &Env) {
+  if (!StatusOrLoc)
+    return false;
+  auto &StatusLoc = locForStatus(*StatusOrLoc);
+  auto *OkVal = Env.get<BoolValue>(locForOk(StatusLoc));
+  return OkVal != nullptr && Env.proves(OkVal->formula());
+}
+
+static ClassTemplateSpecializationDecl *
+getStatusOrBaseClass(const QualType &Ty) {
+  auto *RD = Ty->getAsCXXRecordDecl();
+  if (RD == nullptr)
+    return nullptr;
+  if (isStatusOrType(Ty) ||
+      // In case we are analyzing code under OperatorBase itself that uses
+      // operator* (e.g. to implement operator->).
+      isStatusOrOperatorBaseType(Ty))
+    return cast<ClassTemplateSpecializationDecl>(RD);
+  if (!RD->hasDefinition())
+    return nullptr;
+  for (const auto &Base : RD->bases())
+    if (auto *QT = getStatusOrBaseClass(Base.getType()))
+      return QT;
+  return nullptr;
+}
+
+static QualType getStatusOrValueType(ClassTemplateSpecializationDecl *TRD) {
+  return TRD->getTemplateArgs().get(0).getAsType();
+}
+
+static auto isStatusOrMemberCallWithName(llvm::StringRef member_name) {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return cxxMemberCallExpr(
+      on(expr(unless(cxxThisExpr()))),
+      callee(cxxMethodDecl(
+          hasName(member_name),
+          ofClass(anyOf(statusOrClass(), statusOrOperatorBaseClass())))));
+}
+
+static auto isStatusOrOperatorCallWithName(llvm::StringRef operator_name) {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return cxxOperatorCallExpr(
+      hasOverloadedOperatorName(operator_name),
+      callee(cxxMethodDecl(
+          ofClass(anyOf(statusOrClass(), statusOrOperatorBaseClass())))));
+}
+
+static auto valueCall() {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return anyOf(isStatusOrMemberCallWithName("value"),
+               isStatusOrMemberCallWithName("ValueOrDie"));
+}
+
+static auto valueOperatorCall() {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return expr(anyOf(isStatusOrOperatorCallWithName("*"),
+                    isStatusOrOperatorCallWithName("->")));
+}
+
+static auto
+buildDiagnoseMatchSwitch(const UncheckedStatusOrAccessModelOptions &Options) {
+  return CFGMatchSwitchBuilder<const Environment,
+                               llvm::SmallVector<SourceLocation>>()
+      // StatusOr::value, StatusOr::ValueOrDie
+      .CaseOfCFGStmt<CXXMemberCallExpr>(
+          valueCall(),
+          [](const CXXMemberCallExpr *E,
+             const ast_matchers::MatchFinder::MatchResult &,
+             const Environment &Env) {
+            if (!isSafeUnwrap(getImplicitObjectLocation(*E, Env), Env))
+              return llvm::SmallVector<SourceLocation>({E->getExprLoc()});
+            return llvm::SmallVector<SourceLocation>();
+          })
+
+      // StatusOr::operator*, StatusOr::operator->
+      .CaseOfCFGStmt<CXXOperatorCallExpr>(
+          valueOperatorCall(),
+          [](const CXXOperatorCallExpr *E,
+             const ast_matchers::MatchFinder::MatchResult &,
+             const Environment &Env) {
+            RecordStorageLocation *StatusOrLoc =
+                Env.get<RecordStorageLocation>(*E->getArg(0));
+            if (!isSafeUnwrap(StatusOrLoc, Env))
+              return llvm::SmallVector<SourceLocation>({E->getOperatorLoc()});
+            return llvm::SmallVector<SourceLocation>();
+          })
+      .Build();
+}
+
+UncheckedStatusOrAccessDiagnoser::UncheckedStatusOrAccessDiagnoser(
+    UncheckedStatusOrAccessModelOptions Options)
+    : DiagnoseMatchSwitch(buildDiagnoseMatchSwitch(Options)) {}
+
+llvm::SmallVector<SourceLocation> UncheckedStatusOrAccessDiagnoser::operator()(
+    const CFGElement &Elt, ASTContext &Ctx,
+    const TransferStateForDiagnostics<UncheckedStatusOrAccessModel::Lattice>
+        &State) {
+  return DiagnoseMatchSwitch(Elt, Ctx, State.Env);
+}
+
+BoolValue &initializeStatus(RecordStorageLocation &StatusLoc,
+                            Environment &Env) {
+  auto &OkVal = Env.makeAtomicBoolValue();
+  Env.setValue(locForOk(StatusLoc), OkVal);
+  return OkVal;
+}
+
+BoolValue &initializeStatusOr(RecordStorageLocation &StatusOrLoc,
+                              Environment &Env) {
+  return initializeStatus(locForStatus(StatusOrLoc), Env);
+}
+
+clang::ast_matchers::DeclarationMatcher statusOrClass() {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return classTemplateSpecializationDecl(
+      hasName("absl::StatusOr"),
+      hasTemplateArgument(0, refersToType(type().bind("T"))));
+}
+
+clang::ast_matchers::DeclarationMatcher statusClass() {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return cxxRecordDecl(hasName("absl::Status"));
+}
+
+clang::ast_matchers::DeclarationMatcher statusOrOperatorBaseClass() {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return classTemplateSpecializationDecl(
+      hasName("absl::internal_statusor::OperatorBase"));
+}
+
+clang::ast_matchers::TypeMatcher possiblyAliasedStatusOrType() {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return hasUnqualifiedDesugaredType(
+      recordType(hasDeclaration(statusOrClass())));
+}
+
+clang::ast_matchers::TypeMatcher possiblyAliasedStatusType() {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return hasUnqualifiedDesugaredType(recordType(hasDeclaration(statusClass())));
+}
+
+clang::ast_matchers::TypeMatcher statusOrType() {
+  using namespace ::clang::ast_matchers; // NOLINT: Too many names
+  return hasCanonicalType(qualType(hasDeclaration(statusOrClass())));
+}
+
+bool isRecordTypeWithName(QualType Type, llvm::StringRef TypeName) {
+  return Type->isRecordType() &&
+         Type->getAsCXXRecordDecl()->getQualifiedNameAsString() == TypeName;
----------------
ymand wrote:

This can be quite costly, since it means expanding an arbitrarily complex type name to a string. Instead, compare how this is done surgically by the optional model. But, if this is to be done for an arbitrary name, even better would be to reuse/share code with the hasName matcher, which is optimized for this purpose.

Also, in general, `getQualifiedNameAsString()` should only be used for human consumption. It's not a reliable API for programmatic use.

https://github.com/llvm/llvm-project/pull/162932