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Message-ID: <1063847114.3f6904ca68303@imp.rexursive.com>
Date: Thu, 18 Sep 2003 11:05:14 +1000
From: Bojan Smojver <bojan@rexursive.com>
To: apreq-dev@httpd.apache.org
Subject: Bug in apreq_attr_to_type macro
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The following macro produces unwanted results if P == NULL.

#define apreq_attr_to_type(T,A,P) ( (T*) ((char*)(P)-offsetof(T,A)) )

Basically, you get back a non-NULL value, thus believing that this is an actual
valid memory address. Two problems with that: you can't tell that you actually
found nothing and the code segfaults. Something like this would be a bit better
IMHO:

#define apreq_attr_to_type(T,A,P) \
        ( (P) ? ((T*) ((char*)(P)-offsetof(T,A))) : NULL )

I've tested this in my code and it seems to work, at least for apreq_cookie()
call, which relies on the above macro (through apreq_value_to_cookie macro) to
fetch cookies from the table. I've tested this with Apache 2.0.47 on Red Hat 9.

-- 
Bojan