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Subject: RE: pointers to structs
Date: Wed, 14 Jul 2004 18:20:16 -0400
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Thread-Topic: pointers to structs
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From: "John Bond" <Jbond AT ai-logix DOT com>
To: <djgpp AT delorie DOT com>
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Reply-To: djgpp AT delorie DOT com

You need to allocate the list memory first like so:

list = (struct data_list *) malloc(sizeof(struct data_list));

Then you should check that list != NULL, before using it! -John Bond

YOU WROTE:

-----Original Message-----
From: John Hanley [mailto:jdhanley AT telusplanet DOT net]
Sent: Wednesday, July 14, 2004 6:03 PM
To: djgpp AT delorie DOT com
Subject: pointers to structs


I am creating a linked list.  I have 2 structs:

struct data_record
{
    struct data_record * next;
};

struct data_list
{
    struct data_record * head;
    struct data_record * tail;
};

int main()
{
    struct data_list * list;

    list->head = NULL;
    list->tail = NULL;
}

When I compile then run this, I get:  "Exiting due to Signal SIGSEGV.  Page
Fault at ..."

Can I not assign NULL to these pointers?  If I take the 2 assignments out,
it runs ok.

Any suggestions as to why I can't initialize my head and tail to NULL?

Thanks!

John