PostgreSQL 的语法分析调用关系

最新推荐文章于 2024-06-18 17:53:37 发布

转载最新推荐文章于 2024-06-18 17:53:37 发布 · 124 阅读

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#数据库

本文探讨了在使用Bison构建语法解析器时，如何通过定义宏和设置前缀来定制解析器函数yyparse的行为。解析器函数用于读取标记、执行动作，并在遇到输入结束或无法恢复的语法错误时返回。文章详细解释了不同返回值所代表的意义。

在gram.c 中，有一行：#define yyparse base_yyparse

看gram.y 中，与此对应的是： %name-prefix="base_yy"

而看 bison 的 manual:

http://www.gnu.org/software/bison/manual/html_node/Parser-Function.html

4.1 The Parser Function `yyparse`

You call the function yyparse to cause parsing to occur. This function reads tokens, executes actions, and ultimately returns when it encounters end-of-input or an unrecoverable syntax error. You can also write an action which directs yyparse to return immediately without reading further.

— Function: int yyparse ( void)

The value returned by yyparse is 0 if parsing was successful (return is due to end-of-input).

The value is 1 if parsing failed because of invalid input, i.e., input that contains a syntax error or that causes YYABORT to be invoked.

The value is 2 if parsing failed due to memory exhaustion.