VC进行宏展开的命令

用C/C++做开发时，有很多的宏命令，绕来绕去的，很难看清楚关系。一般的编译器都提供了展开的命令，VC下的命令如下：

CL /EP /C YourCodeFile.cpp

This command will carry out all preprocessor directives and expand macros in the C++ code file "YourCodeFile.cpp". The/EP option suppresses compilation. /EP also suppresses the output files from the /FA, /Fa, and /Fm options. The/C (Preserve Comments During Preprocessing) option is used to preserve comments in the preprocessed output.

这个是从msdn上摘下来的，除了可以用于cpp文件之外，还可以用于.h头文件。

我将v8的ast.h展开后可以看见他的astNode类的定义：

class AstNode: public ZoneObject {
 public:
#define DECLARE_TYPE_ENUM(type) k##type,
  enum Type {
    AST_NODE_LIST(DECLARE_TYPE_ENUM)
    kInvalid = -1
  };
#undef DECLARE_TYPE_ENUM

.....
  virtual void Accept(AstVisitor* v) = 0;
  virtual Type node_type() const = 0;

  // Type testing & conversion functions overridden by concrete subclasses.
#define DECLARE_NODE_FUNCTIONS(type)                  \
  bool Is##type() { return node_type() == AstNode::k##type; }          \
  type* As##type() { return Is##type() ? reinterpret_cast<type*>(this) : NULL; }
  AST_NODE_LIST(DECLARE_NODE_FUNCTIONS)
#undef DECLARE_NODE_FUNCTIONS
...
} 
           

将无关的代码略掉了。展开后的结果如下：

class AstNode: public ZoneObject {
 public:

  enum Type {
    kVariableDeclaration, kFunctionDeclaration, kModuleDeclaration, kImportDeclaration, kExportDeclaration, kModuleLiteral, kModuleVariable, kModulePath, 
	kModuleUrl, kBlock, kExpressionStatement, kEmptyStatement, kIfStatement, kContinueStatement, kBreakStatement, kReturnStatement, kWithStatement, 
	kSwitchStatement, kDoWhileStatement, kWhileStatement, kForStatement, kForInStatement, kTryCatchStatement, kTryFinallyStatement, kDebuggerStatement, 
	kFunctionLiteral, kSharedFunctionInfoLiteral, kConditional, kVariableProxy, kLiteral, kRegExpLiteral, kObjectLiteral, kArrayLiteral, kAssignment, 
	kThrow, kProperty, kCall, kCallNew, kCallRuntime, kUnaryOperation, kCountOperation, kBinaryOperation, kCompareOperation, kThisFunction,
    kInvalid = -1
  };

  virtual void Accept(AstVisitor* v) = 0;
  virtual Type node_type() const = 0;

  // Type testing & conversion functions overridden by concrete subclasses.

  bool IsVariableDeclaration() { return node_type() == AstNode::kVariableDeclaration; } 
  VariableDeclaration* AsVariableDeclaration() { return IsVariableDeclaration() ? reinterpret_cast<VariableDeclaration*>(this) : NULL; } 
  bool IsFunctionDeclaration() { return node_type() == AstNode::kFunctionDeclaration; } 
  FunctionDeclaration* AsFunctionDeclaration() { return IsFunctionDeclaration() ? reinterpret_cast<FunctionDeclaration*>(this) : NULL; } 
  bool IsModuleDeclaration() { return node_type() == AstNode::kModuleDeclaration; } 
  ModuleDeclaration* AsModuleDeclaration() { return IsModuleDeclaration() ? reinterpret_cast<ModuleDeclaration*>(this) : NULL; } 
.......
           

一目了然，很好看懂了类的结构了吧...