[SOLVED] C

golmschenk · 03-07-2010, 04:51 PM

First off, thanks for everyone who's helped me so far. I know I've been asking a lot of questions.

How do you malloc a struct in C? I have a structure of the form:

Code:

typedef struct child_req_to_parent
{
	req_type type;
	child_request req;
}child_req_to_parent;

I basically want to allocate the space using malloc so that I can use free at a later time multiple times. I've been trying to implement it by

Code:

struct child_req_to_parent Router_Buf;
Router_Buf = (Router_Buf*)malloc(sizeof(Router_Buf));

But this is clearly wrong. If someone could help me with using malloc on such a struct it would be great. Thanks!

troop · 03-07-2010, 04:57 PM

Code:

typedef struct child_req_to_parent
{
	req_type type;
	child_request req;
};

struct child_req_to_parent *Router_Buf;
Router_Buf = (struct child_req_to_parent*)malloc(sizeof(struct child_req_to_parent));

neonsignal · 03-07-2010, 05:00 PM

You are very close:

Code:

typedef struct
{
	req_type type;
	child_request req;
}child_req_to_parent;
...
child_req_to_parent *pRouter_Buf;
pRouter_Buf = (child_req_to_parent *)malloc(sizeof(child_req_to_parent));

== edit ==
same as above!

PTrenholme · 03-07-2010, 05:13 PM

You could also use calloc which does the computation "inside." See man calloc for details.

ForzaItalia2006 · 03-08-2010, 05:58 AM

Hey,

you could also write:

Code:

typedef struct
{
	req_type type;
	child_request req;
}child_req_to_parent;
...
child_req_to_parent *pRouter_Buf;
pRouter_Buf = malloc(sizeof(*pRouter_Buf));

The advantage is that could change the type of pRouter_Buf without changing the (m)allocation statement. Though, this reduces the risk of errors caused by source code refactoring AND, you don't have to type too many characaters ... :-)

- Andi -

golmschenk · 03-08-2010, 12:16 PM

Great! Thanks everyone!