Date: Mon, 13 May 2002 19:35:20 +0200 From: Jens Rehsack <rehsack@liwing.de> To: Paul Everlund <tdv94ped@cs.umu.se> Cc: freebsd-questions@freebsd.org Subject: Re: C malloc question Message-ID: <3CDFF958.C850E528@liwing.de> References: <Pine.GSO.4.33.0205131845160.22929-100000@gren.cs.umu.se>
next in thread | previous in thread | raw e-mail | index | archive | help
Paul Everlund wrote:
>
> Hi all!
>
> I have a question regarding malloc and returning arrays in C.
>
> The following C program is an example.
>
> #include <stdlib.h>
> #include <string.h>
>
> static char *init()
> {
> char *str;
> int i;
>
> str = (char *)malloc(sizeof(char), 128);
malloc doesn't have 2 params
> for(i = 0; i < 127; i++)
> str[i] = "A";
> str[i] = '\0';
> return str;
> }
>
> int main()
> {
> int i;
>
> for(i = 0; i < 500000; i++)
> init();
> printf("%s\n", init());
> return 0;
> }
>
> This program takes up a lot of malloc'ed memory after a while,
> so how do one return arrays and free memory in the main function
> everytime the array have been used? I would like to not use fix-
> ed size arrays, as the real function should be general enough
> to handle all kind of array sizes.
>
> As the size is known in the main function, I guess I could send
> in a buffer to get the data, as in init(char *buf), but I would
> like to avoid this.
>
> What is the best solution for this problem?
Because it's a very small sample, I do not really see the goal...
Maybe a solution is
typedef struct object_t {
size_t array_size
char *ptr2array;
} object_t;
static int
init( struct object_t *obj )
{
int rc = 0;
if( object )
{
if( NULL != obj->ptr2array )
free( obj->ptr2array );
if( NULL != ( obj->ptr2array = calloc( WANTED_ARRAY_SIZE, sizeof(char) ) ) )
{
obj->array_size = WANTED_ARRAY_SIZE;
++rc;
}
}
return rc;
}
int
main(void)
{
int i;
object_t obj = { 0, NULL };
for(i = 0; i < 500000; i++)
init( &obj ); /* FIXME: check return code */
printf( "%s\n", obj->ptr2array );
return 0;
}
> Thanks a lot in advance!
>
> Best regards,
> Paul
>
> To Unsubscribe: send mail to majordomo@FreeBSD.org
> with "unsubscribe freebsd-questions" in the body of the message
--
L i W W W i Jens Rehsack
L W W W
L i W W W W i nnn gggg LiWing IT-Services
L i W W W W i n n g g
LLLL i W W i n n g g Friesenstraße 2
gggg 06112 Halle
g
g g
Tel.: +49 - 3 45 - 5 17 05 91 ggg e-Mail: <rehsack@liwing.de>
Fax: +49 - 3 45 - 5 17 05 92 http://www.liwing.de/
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3CDFF958.C850E528>