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md = (struct mailbox_data *)malloc(sizeof(struct mailbox_data),KERNEL);

Problem understanding the malloc() funktion. Can it really take two
parametres?? And what about the pointer - what does it point to??

thanks
Allan, newbie in c-programming

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holst skrev:

>md = (struct mailbox_data *)malloc(sizeof(struct mailbox_data),KERNEL);

>Problem understanding the malloc() funktion. Can it really take two
>parametres?

Not in ANSI-C. It might be a local function written inside the
code.

>And what about the pointer - what does it point to?

When using malloc (the standard C-function), a chunk of memory is
reserved and the pointer, here md, will point to the (first byte
of the) chunk.

The parenthesis, (struct mailbox_data *), is a typecast that
makes sure that md is not just any pointer but a pointer to a
specific type. That will be important later in the program.

--
Bertel
http://lundhansen.dk/bertel/   FIDUSO: http://fiduso.dk/

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Thanks..

"Bertel Lund Hansen" <nospamto@lundhansen.dk> wrote in message
news:tojfftg23ra2e1vphb64blpd8esmenugk1@sunsite.auc.dk...
> holst skrev:
>
> >md = (struct mailbox_data *)malloc(sizeof(struct mailbox_data),KERNEL);
>
> >Problem understanding the malloc() funktion. Can it really take two
> >parametres?
>
> Not in ANSI-C. It might be a local function written inside the
> code.
>
> >And what about the pointer - what does it point to?
>
> When using malloc (the standard C-function), a chunk of memory is
> reserved and the pointer, here md, will point to the (first byte
> of the) chunk.
>
> The parenthesis, (struct mailbox_data *), is a typecast that
> makes sure that md is not just any pointer but a pointer to a
> specific type. That will be important later in the program.
>
> --
> Bertel
> http://lundhansen.dk/bertel/ FIDUSO: http://fiduso.dk/