clang——CFG构成与生成（一）

最新推荐文章于 2023-06-19 21:15:35 发布

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最新推荐文章于 2023-06-19 21:15:35 发布 · 4.6k 阅读

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CC 4.0 BY-SA版权

本文介绍了Clang中的CFG（Control Flow Graph）元素，包括CFGBlock的基础元素CFGElement，如CFGStmt和CFGInitializer。CFGElement的种类涵盖各种语句和表达式，特别是对隐式析构函数的表示。CFGBlock由声明/表达式集合、CFGTerminator和前驱/后继列表构成，而CFG对象则包含了整个CFGBlock的集合，包括Entry和Exit Block。重点讨论了如何使用placement new生成新的CFGBlock。

CFGElement CFGBlock的最基本元素

enum Kind {
    // main kind
    Statement,
    Initializer,
    NewAllocator,
    // dtor kind
    AutomaticObjectDtor,
    DeleteDtor,
    BaseDtor,
    MemberDtor,
    TemporaryDtor,
    DTOR_BEGIN = AutomaticObjectDtor,
    DTOR_END = TemporaryDtor
  };

代表具体每一条语句，Terminator除外

CFGElement每种kind都有一个相应的子类，如

class CFGStmt : public CFGElement {
public:
  CFGStmt(Stmt *S) : CFGElement(Statement, S) {}

  const Stmt *getStmt() const {
    return static_cast<const Stmt *>(Data1.getPointer());
  }

private:
  friend class CFGElement;
  CFGStmt() {}
  static bool isKind(const CFGElement &E) {
    return E.getKind() == Statement;
  }
};

CFGStmt代表普通的语句

/// CFGInitializer - Represents C++ base or member initializer from
/// constructor's initialization list.
class CFGInitializer : public CFGElement {
public:
  CFGInitializer(CXXCtorInitializer *initializer)
      : CFGElement(Initializer, initializer) {}

  CXXCtorInitializer* getInitializer() const {
    return static_cast<CXXCtorInitializer*>(Data1.getPointer());
  }

private:
  friend class CFGElement;
  CFGInitializer() {}
  static bool isKind(const CFGElement &E) {
    return E.getKind() == Initializer;
  }
};

CFGInitializer表示构造函数的初始化列表

/// CFGNewAllocator - Represents C++ allocator call.
class CFGNewAllocator : public CFGElement {
public:
  explicit CFGNewAllocator(const CXXNewExpr *S)
    : CFGElement(NewAllocator, S) {}

  // Get the new expression.
  const CXXNewExpr *getAllocatorExpr() const {
    return static_cast<CXXNewExpr *>(Data1.getPointer());
  }

private:
  friend class CFGElement;
  CFGNewAllocator() {}
  static b