parsing - 如何解析依赖于父节点信息的子节点？

Question

如果我像这样在 Yacc/Bison 中编写语法文件:

Module
    :ModuleName "=" Functions
      { $$ = Builder::concat($1, $2, ","); }

Functions
    :Functions Function
      { $$ = Builder::concat($1, $2, ","); }
    | Function
      { $$ = $1; }

Function
    : DEF ID ARGS BODY
      {
          /** Lacks module name to do name mangling for the function **/
          /** How can I obtain the "parent" node's module name here ?? **/
          module_name = ; //????

          $$ = Builder::def_function(module_name, $ID, $ARGS, $BODY); 
      }

这个解析器应该解析如下代码:

main_module:
    def funA (a,b,c) { ... }

在我的 AST 中，名称“funA”应重命名为 main_module.funA。但是当解析器处理 Function 节点时我无法获取模块的信息!

是否有任何 Yacc/Bison 工具可以帮助我处理这个问题，或者我应该改变我的解析风格以避免这种尴尬的情况？

Answer 1

有一个 bison 功能，但如 manual说，小心使用:

$N with N zero or negative is allowed for reference to tokens and groupings on the stack before those that match the current rule. This is a very risky practice, and to use it reliably you must be certain of the context in which the rule is applied. Here is a case in which you can use this reliably:

 foo:      expr bar '+' expr  { ... }
         | expr bar '-' expr  { ... }
         ;

 bar:      /* empty */
         { previous_expr = $0; }
         ;

As long as bar is used only in the fashion shown here, $0 always refers to the expr which precedes bar in the definition of foo.

更干净地说，您可以使用中间规则操作(在模块中)将模块名称推送到名称堆栈上(这必须是解析上下文的一部分)。然后，您将在规则末尾弹出堆栈。

有关中间规则操作的更多信息和示例，请参阅manual .