c - Allocating and free object of structures -

gcc 4.4.4 c89

i have following code in channel.h file

typedef struct channel_tag channel_t;  channel_t* open_channel(size_t channel_id); void close_channel(channel_t *channel); 

and in channel.c file

#include "channel.h"  struct channel_tag {     size_t channel_id; };  channel_t* open_channel(size_t channel_id) {     channel_t *channel = malloc(sizeof *channel);      if(channel == null) {         fprintf(stderr, "cannot allocate memory\n");         return null;     }      channel->channel_id = channel_id;     printf("channel [ %zu ] has been created\n", channel->channel_id);      return channel; }  void close_channel(channel_t *channel) {     printf("channel [ %zu ] resources has been released\n", channel->channel_id);     free(channel); } 

the problem main.c file. here have loop create 5 channel objects , allocates memory them. however, if wanted free them later in program, not sure how can reference them. 5 testing with. later 300.

int main(void) {     size_t = 0;      channel_t *channel = null;      for(i = 0; < 4; i++) {         channel = open_channel(i);          if(channel == null) {             fprintf(stderr, "cannot create channel [ %zu ]\n", i);         }     }      /* stuff channels , free them before program exists.         however, need loop , pass of them, not 1 */     for(i = 0; < 4; i++) {        close_channel(channel);     }     return 0; } 

many suggestions,

store channels in array create them. make sure can tell whether mallocs worked or not @ end of program (hence memset in code).

channel_t **channel = malloc(5 * sizeof(channel_t*)); memset(channel, 0, 5 * sizeof(channel_t*));  for(i = 0; < 5; i++) {     channel[i] = open_channel(i);      if(channel[i] == null) {         fprintf(stderr, "cannot create channel [ %zu ]\n", i);     } }  /* stuff channels , free them before program exists.     however, need loop , pass of them, not 1 */ for(i = 0; < 5; i++) {    if (channel[i] != null)  /* handle case of opens failed */    {      close_channel(channel[i]);    } }  free(channel);