[clang] [clang][analyzer] Add StoreToImmutable checker (PR #150417)

[Endre Fülöp via cfe-commits]

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+//=== StoreToImmutableChecker.cpp - Store to immutable memory ---*- 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 file defines StoreToImmutableChecker, a checker that detects writes
+// to immutable memory regions. This implements part of SEI CERT Rule ENV30-C.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.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/MemRegion.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class StoreToImmutableChecker : public Checker<check::Bind> {
+  const BugType BT{this, "Write to immutable memory", "CERT Environment (ENV)"};
+
+public:
+  void checkBind(SVal Loc, SVal Val, const Stmt *S, CheckerContext &C) const;
+
+private:
+  bool isInitializationContext(const Stmt *S, CheckerContext &C) const;
+  bool isEffectivelyConstRegion(const MemRegion *MR, CheckerContext &C) const;
+};
+} // end anonymous namespace
+
+bool StoreToImmutableChecker::isInitializationContext(const Stmt *S,
+                                                      CheckerContext &C) const {
+  // Check if this is a DeclStmt (variable declaration)
+  if (isa<DeclStmt>(S))
+    return true;
+
+  // This part is specific for initialization of const lambdas pre-C++17.
+  // Lets look at the AST of the statement:
+  // ```
+  // const auto lambda = [](){};
+  // ```
+  //
+  // The relevant part of the AST for this case prior to C++17 is:
+  // ...
+  // `-DeclStmt
+  //   `-VarDecl
+  //     `-ExprWithCleanups
+  //       `-CXXConstructExpr
+  // ...
+  // In C++17 and later, the AST is different:
+  // ...
+  // `-DeclStmt
+  //   `-VarDecl
+  //     `-ImplicitCastExpr
+  //       `-LambdaExpr
+  //         |-CXXRecordDecl
+  //         `-CXXConstructExpr
+  // ...
+  // And even beside this, the statement `S` that is given to the checkBind
+  // callback is the VarDecl in C++17 and later, and the CXXConstructExpr in
+  // C++14 and before. So in order to support the C++14 we need the following
+  // ugly hack to detect whether this construction is used to initialize a
+  // variable.
+  //
+  // FIXME: This should be eliminated once the API of checkBind would allow to
+  // distinguish between initialization and assignment, because this information
+  // is already available in the engine, it is just not passed to the checker
+  // API.
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gamesh411 wrote:

Added this with a sidenote.

https://github.com/llvm/llvm-project/pull/150417