[Gllug] Bison question

[rich at annexia.org]

I don't know if anyone knows anything about bison/yacc, but here goes ...

I have a bison rule which looks like this:

%union {
	char *filename;
 ...
}

%type <filename> filename

%%

filename
        : STRING
          {
            $$ = strdup (mp_string);
          }
     '(' props ')'
          {
            /* Make sure the file exists. */
            file_add ($$);

            /* Add the properties to the file. */
            file_set_props ($$, $<props>3);
          }
      ;

The idea is that the first clause saves mp_string (which is likely
to get overwritten by parsing the 'props' non-terminal). Then in the
second clause we call file_add with the saved filename. But tracing
this in gdb, I find that by the time we get to file_add, $$ is equal
to NULL (not my saved char *).

Any ideas why this is?

Do I need to use a global variable for this sort of thing?

Rich.

-- 
Richard Jones, Red Hat Inc. (London, UK) http://www.redhat.com/software/ccm
http://www.annexia.org/ Freshmeat projects: http://freshmeat.net/users/rwmj

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