[SOLVED] C

golmschenk · 03-20-2010, 04:41 PM

So far I have this:

Code:

int mm_init (mm_t *MM, int hm, int sz) {
	int i;
	for (i=0;i<hm;i++)
	{
	MM->Mem_Chunk[i]=(void*)malloc(sz);
	MM->Mem_Chunk_Used[i]=0;	//initially, no chunks are in use
	if (MM->Mem_Chunk[i] == -1) return -1;
	}
	MM->MAX_CHUNKS=hm;
	return 0;
}

With the struct defined as:

Code:

typedef struct {
void *Mem_Chunk;
int *Mem_Chunk_Used;
int MAX_CHUNKS;
} mm_t;

Right now I know that malloc is being casted to a void instead of a void pointer. How can I get it to be cast as a void pointer? Thanks for your time!

Sergei Steshenko · 03-20-2010, 04:46 PM

Quote:

Originally Posted by golmschenk

So far I have this:

Code:

int mm_init (mm_t *MM, int hm, int sz) {
	int i;
	for (i=0;i<hm;i++)
	{
	MM->Mem_Chunk[i]=(void*)malloc(sz);
	MM->Mem_Chunk_Used[i]=0;	//initially, no chunks are in use
	if (MM->Mem_Chunk[i] == -1) return -1;
	}
	MM->MAX_CHUNKS=hm;
	return 0;
}

With the struct defined as:

Code:

typedef struct {
void *Mem_Chunk;
int *Mem_Chunk_Used;
int MAX_CHUNKS;
} mm_t;

Right now I know that malloc is being casted to a void instead of a void pointer. How can I get it to be cast as a void pointer? Thanks for your time!

Your

Code:

(void*)malloc(sz);

casts to pointer to void, and this is what it should do according to

Code:

void *Mem_Chunk;

.

For readability/similarity you could have written

Code:

(void*)malloc(sz);

as

Code:

(void *)malloc(sz);

.

irmin · 03-20-2010, 04:47 PM

You will have to use the data type void** for Mem_Chunk. This because you cannot create objects of type void, only pointers to void* are valid. Thus you will need Mem_Chunk to be either an array of void* or void**. But you will have to allocate space for Mem_Chunk and Mem_Chunk_Used, too: Somewhere the addresses of each chunk allocated by malloc must by stored:

Code:

typedef struct {
void **Mem_Chunk;
int *Mem_Chunk_Used;
int MAX_CHUNKS;
} mm_t;

int mm_init (mm_t *MM, int hm, int sz) {
	int i;
 MM->Mem_Chunk = malloc( sizeof(void*) * hm );
 MM->Mem_Chunk_Used = malloc( sizeof(int) * hm );
	for (i=0;i<hm;i++)
	{
	MM->Mem_Chunk[i]=(void*)malloc(sz);
	MM->Mem_Chunk_Used[i]=0;	//initially, no chunks are in use
	if (MM->Mem_Chunk[i] == -1) return -1;
	}
	MM->MAX_CHUNKS=hm;
	return 0;
}

golmschenk · 03-20-2010, 04:53 PM

Worked perfectly irmin. Thanks a bunch.

golmschenk · 03-20-2010, 05:21 PM

Actually, if I take what you gave me and just comment out a few parts:

Code:

typedef struct {
void **Mem_Chunk;
int *Mem_Chunk_Used;
int MAX_CHUNKS;
} mm_t;

int mm_init (mm_t *MM, int hm, int sz) {
	int i;
 //MM->Mem_Chunk = malloc( sizeof(void*) * hm );    //commented out here
 //MM->Mem_Chunk_Used = malloc( sizeof(int) * hm );    //commented out here
	for (i=0;i<hm;i++)
	{
	MM->Mem_Chunk[i]= /*(void*)*/ malloc(sz);    //commented out a part here
	MM->Mem_Chunk_Used[i]=0;
	if (MM->Mem_Chunk[i] == -1) return -1;
	}
	MM->MAX_CHUNKS=hm;
	return 0;
}

Then that gives me more of what I was looking for. Then I don't have to malloc the multiple times ahead of time too. Thanks!