Ok say I have this
char* construct_keyname(char *key, char *postfix){
char *keyname;
keyname = (char *)malloc(KEY_SIZE*sizeof(char)); //allocate
memory that is freed inmemcache_gstr and memcache_gid
snprintf(keyname,
(
(strlen(MEMCACHE_PRFX)+strlen(postfix)+strlen(key))
+3
),
"%s%s_%s",
MEMCACHE_PRFX,
key,
postfix);
return keyname;
}
I have allocated memory for the prefix name
char *memcache_gstr(char *key, int id){
char *ret;
char *keyname;
char keyid[4];
sprintf(keyid,"%d",id);
keyname= construct_keyname(key,keyid);
printf("key: %sn", keyname);
ret = getmc(keyname);
free(keyname);
return ret;
}
then I call it here and since the return value of the keyname
constructor is allocated memory can I free it with the pointer that I
assigned to it? ie: keyname
keyname is a pointer that points to the return value of
construct_keyname() and the return value is allocated on the "heap".
Is that right?
On 04/01/2012 at 7:51 AM, Paul J Stevens wrote:On 04/01/2012 02:38
AM, skr...@hushmail.com wrote:
> https://github.com/skrapsrwt/dbmail-memcache/
I looked at the 'push change and added some comments.
Most importantly you need to understand C doesn't have automatic
allocation/de-allocation of memory like PHP does.
If you want to assign something to a chunk of memory that memory must
be
allocated, either on the 'stack', or on the 'heap'.
The stack is local to the scope. So it can be passed 'down-stream' if
you are careful, but it can never be returned to the calling scope.
The heap is where malloc/free do their thing: a global memory space
that
you can use - if you use it following the rules. Heap memory is always
safe to pass around.
- you must allocated everything you need.
- for each malloc call, there must be a free call.
stack allocation:
char foo[128]; // char array on the stack you can assign 128 bytes to
char *foo = g_new0(char, 128); // same size char array on the heap
g_new0 is a simple wrapper around calloc. It allocates memory and
cleans
it out.
If you allocate on the stack it is always a good idea to clean it
explicitely:
char foo[128];
memset(foo, 0, sizeof(foo));
--
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