Using linked lists with Bison

Suppose my YYSTYPE is a struct with a pointer to the 开发者_开发问答next struct. Can I direct that pointer to YYSTYPE values of other grammar variables, or are their YYSTYPE values local and will disappear after the derivation ends, causing a segfault later on.

YYSTYPE is the type of variables on Yacc's expression stack.

If the pointers you create are to items actually stored in Yacc's stack, which would typically be done by referencing $1 (or &$1 to get the pointer), then you are indeed pointing to data that will be released and reused, and are in for a world of hurt (such as segmentation faults if you're lucky; confusion and mishandled information if you're unlucky).

If the pointers you create are to items of type YYSTYPE that you manage, then of course there is no problem; you manage their duration, not Yacc.

Copy anything you need from things like $1 into your own storage.