malloc + Automatic Reference Counting?

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malloc(sizeof)
malloc implementation
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void *malloc

If I use malloc along with Automatic Reference Counting, do I still have to manually free the memory?

int a[100];
int *b = malloc(sizeof(int) * 100);
free(b);

Yes, you have to code the call to free yourself. However, your pointer may participate in the reference counting system indirectly if you put it in an instance of a reference-counted object:

@interface MyObj : NSObject {
    int *buf;
}
@end

@implementation MyObj

-(id)init {
    self = [super init];
    if (self) {
        buf = malloc(100*sizeof(int));
    }
}
-(void)dealloc {
    free(buf);
}

@end

There is no way around writing that call to free - one way or the other, you have to have it in your code.

C library function - malloc(), C library function - malloc() - The C library function void *malloc(size_t size) allocates the requested memory and returns a pointer to it. Allocates a block of size bytes of memory, returning a pointer to the beginning of the block. The content of the newly allocated block of memory is not initialized, remaining with indeterminate values.

Yes. ARC only applies to Objective-C instances, and does not apply to malloc() and free().

malloc - C++ Reference, malloc. void* malloc (size_t size);. Allocate memory block. Allocates a block of size bytes of memory, returning a pointer to the beginning of the block. The malloc function allocates a memory block of at least size bytes. The block may be larger than size bytes because of the space that's required for alignment and maintenance information. malloc sets errno to ENOMEM if a memory allocation fails or if the amount of memory requested exceeds _HEAP_MAXREQ.

In dealloc add an if not nil and assign to nil for safe. Dont want to free nil, malloc might be used outside of init etc.

@interface MyObj : NSObject {
    int *buf;
}
@end

@implementation MyObj

-(id)init {
    self = [super init];
    if (self) {
        buf = malloc(100*sizeof(int));
    }
}

-(void)dealloc {
    if(buf != null) {
        free(buf);
        buf = null;
    }
}

@end

malloc, The malloc() function shall allocate unused space for an object whose size in bytes is specified by size and whose value is unspecified. The order and contiguity of  The malloc () function stands for memory allocation. It is a function which is used to allocate a block of memory dynamically. It reserves memory space of specified size and returns the null pointer pointing to the memory location. The pointer returned is usually of type void.

Some 'NoCopy' variants of NSData can be paired with a call to malloc which will free you from having to free anything.

NSMutableData can be used as somewhat higher-overhead version of calloc which provides the convenience and safety of ARC.

C dynamic memory allocation, returns. When the memory is no longer needed, the pointer is passed to free which deallocates the memory so that it can be used for other purposes. The malloc () Function in C Up until now in our programs, we have been using static memory allocation. In static memory allocation the size of the program is fixed, we can not increase or decrease size while the program is running. So why would we actually want to increase or decrease the size of the program while the program is running ?

C Dynamic Memory Allocation Using malloc(), calloc(), free , . The malloc() function reserves a block of memory of the specified number of bytes. And, it returns a pointer of void which can be casted into pointers of any form. void* malloc(size_t size); Allocates size bytes of uninitialized storage. If allocation succeeds, returns a pointer that is suitably aligned for any object type with fundamental alignment. If size is zero, the behavior of malloc is implementation-defined.

C Programming/stdlib.h/malloc, () allocates the memory and also initializes the allocated memory block to zero. dlmalloc is a boundary tag allocator. Memory on the heap is allocated as "chunks", an 8-byte aligned data structure which contains a header, and usable memory. Allocated memory contains an 8 or 16 byte overhead for the size of the chunk and usage flags.

Difference Between malloc() and calloc() with Examples , malloc() takes a single argument (the amount of memory to allocate in bytes), while calloc() needs two arguments (the number of variables to allocate in memory,  The function calloc () stands for contiguous location. It works similar to the malloc () but it allocate the multiple blocks of memory each of same size. Here is the syntax of calloc () in C language, void *calloc (size_t number, size_t size);

Comments
  • So ARC will call dealloc when it removes the instance?
  • @stas Well, not directly: ARC will call [obj release] - that's its only job. Only when releasing results in ref counting going down to zero, the [obj dealloc] is called.
  • No. ARC only handles Objective-C instances created with [ClassName alloc].
  • Sorry, but could you tell me if a struct made by 'Vertex v;' would count as an Objective-C instance?
  • No, Vertex v; does not do any heap memory allocation. As a local variable, it would be allocated on the stack and automatically discarded when the scope exits. As part of another structure or object, it would be subject to the deallocation rules of the containing object.
  • stas: int[100] wouldn't be a valid argument to free() anyway, since it would be allocated on the stack.
  • I don't understand why you check if buf != NULL in dealloc. Shouldn't you instead check if buf == NULL after the malloc in init, and if so, handle that error? Then, there's no need to check if buf != NULL in dealloc, right? Also, what's the point of setting buf = NULL at the end of dealloc? Especially, if buf is a private instance variable, wouldn't you have to be doing something pretty weird in your code in order to access buf after dealloc is called?
  • You are right. The only reason for the if is to avoid calling free(null) to avoid a crash. Just tested, free(null) does not crash.