c++ - Was sind die Syntaxregeln für ## in define?

Question

In jdk8源码的allocation.hpp gibt es

#define METASPACE_OBJ_TYPE_DECLARE(name) name ## Type,
#define METASPACE_OBJ_TYPE_NAME_CASE(name) case name ## Type: return #name;

  enum Type {
    // Types are MetaspaceObj::ClassType, MetaspaceObj::SymbolType, etc
    METASPACE_OBJ_TYPES_DO(METASPACE_OBJ_TYPE_DECLARE)
    _number_of_types
  };

Ich verstehe die grammatikalischen Regeln nicht in ## 在 define.

Answer 1

#define是定义变量,2个##是连接运算符,可以查看

Answer 2

## 是连接运算符，参见 https://stackoverflow.com/que...