gcc奇怪的宏定义

kenby

在看gcc源代码的时候发现一种很奇怪的宏定义方式
#define DEFTREECODE(SYM, STRING, TYPE, NARGS)   SYM,
  enum tree_code {
       #include "tree.def"
  };
tree.def文件里面的内容如下:
DEFTREECODE (ERROR_MARK, "error_mark", "x", 0)
DEFTREECODE (IDENTIFIER_NODE, "identifier_node", "x", -1)
DEFTREECODE (OP_IDENTIFIER, "op_identifier", "x", 2)
DEFTREECODE (TREE_LIST, "tree_list", "x", 2)
....
等很多类似的东西,
不知道这样做有什么作用，这样定义出来的tree_code代表什么意思呢？

雨过白鹭洲

没看明白

nicozhou

应该是用来定义和树的节点相关的信息的

heixia108

gcc-implementation-details(见附件) 4.1节中有如下说明：

The tree.def file contains various node names defined using a C preprocessor macro – DEFTREECODE. The macro is used in different ways depending on the information required. We illustrate the use with an example. Consider the following macro that is represents the C void type: DEFTREECODE (VOID_TYPE, "void_type", ’t’, 0) Defining the DEFTREECODE macro as: #define DEFTREECODE(arg1, arg2, arg3, arg4) arg2 yields the second argument which gives the name as a string. The definitions of the DEFTREECODE are changed as needed in the GCC sources. For instance, the various nodes are enumerated simply as: #define DEFTREECODE(arg1, arg2, arg3, arg4) arg1 enum tree_node_list { #include "tree.def" }; #undef DEFTREECODE The technique is used at many places in the source, for example for the RTL definitions too. The first argument of the DEFTREECODE macro is the symbolic name of the node typically used to create an enumerated data type of nodes. The second argument is the identifier used to refer to that node. The nodes in the GCC AST are of different kinds as listed in [kinds of AST nodes in GCC], page 16. These kinds are encoded via a set of character codes which are listed in tree.def. These codes are the third argument of the DEFTREECODE macro. The fourth argument in most node definitions is the number of operands of that node. For other nodes, the use of the fourth argument is dependent on the node being described. The collection of the DEFTREECODE macros define the database of nodes that GCC uses for it’s AST.

gcc-implementation-details.pdf (366.26 KB, 下载次数: 77)

2008-11-22 08:54 上传

点击文件名下载附件

[ 本帖最后由 heixia108 于 2008-11-22 08:55 编辑 ]

kenby

恩，差不多明白了。不知这个pdf在哪里下的？有没有gcc2.0的？

heixia108

http://gcc.gnu.org/wiki

kenby

楼上，你QQ号或msn是？看了你的博客，想一起交流。

heixia108

给你发消息了，呵，希望有机会和你交流