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[Question / Bison 1.875c]: %destructorS not being called at all?

From: Jeannot_Langlois
Subject: [Question / Bison 1.875c]: %destructorS not being called at all?
Date: Mon, 01 Mar 2004 19:54:08 -0500
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.2) Gecko/20030208 Netscape/7.02

Hi there,

I am currently using Bison 1.875c (compiled cleanly with gcc 3.2.2) to implement a reentrant GLR parser in C.  I am using many "%destructor" instructions on string (char*) types, such as this example extracted from my ircparser.y file:



%union  /* data types */
    char chr;         /* character */
    char* str;        /* string */


%type <str> R_MESSAGE


    free ($$);
    $$ = NULL;



I've put simple "printf" statements in all my "%destructor"s, so I can verify that they get properly called when string (char*) types need to be freed.

While my grammar successfully gets translated in C by bison, then gets compiled properly by gcc, and is then executed with *NO* apparent errors in runtime, the "printf" statements never get displayed on screen, and the parser executable terminates [normally] and I finally get my unix prompt back (as expected).

It seems to me that the "%destructor"s are *NOT* called (as I would expect) to free the malloc'ed memory at the end of the runtime.

Shouldn't these "%destructor"s be called automatically?  Or am I doing something wrong (or misunderstanding anything)?  In either case, has anybody seen this behavior before, and how can I ensure that memory allocated by "malloc" in semantic actions gets properly freed by "%destructor"s ?

I'd be glad to provide information regarding this issue if required.


Jeannot Langlois - Signature Jeannot Langlois
B. Sc.  Computer Science / B. Sc.  Informatique
Software Developer / Programmeur-Analyste
System/Network Administrator / Administrateur Système/Réseau


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