Dynamic-Malloc

In this project I wrote a dynamic storage allocator for C programs, i.e., my own version of the malloc , free , and realloc routines. You are encouraged to explore the design space creatively and implement an allocator that is correct, efficient, and fast.

Description

Your dynamic storage allocator will consist of the following four functions, which are declared in mm.h and defined in mm.c .

• int mm_init(void);
• void *mm_malloc(size_t size);
• void mm_free(void *ptr);
• void *mm_realloc(void *ptr, size_t size); The mm.c file we have given you implements a simple memory allocator based on an implicit free list, first fit placement, and boundary tag coalescing, as described in the textbook. Using this as a starting place, modify these functions (and possibly define other private static functions), so that they obey the following semantics:
• mm_init:Before calling mm_malloc , mm_realloc , or mm_free , the application program (i.e., the trace-drive n driver program that you will use to evaluate your implementation) calls mm_init to perform any necessary initializations, such as allocating the initial heap area. The return value should be −1 if there was a problem in performing the initialization, 0 otherwise.

The driver will call mm_init before running each trace (and after resetting the brk pointer). Therefore, your mm_init function should be able to reinitialize all state in your allocator each time it is called. In other words, you should not assume that it will only be called once.

• mm_malloc: The mm_malloc routine returns a pointer to an allocated block payload of at least size bytes. The entire allocated block should lie within the heap region and should not overlap with any other allocated chunk. We will compare your implementation to the version of malloc supplied in the standard C library ( libc ). Since the libc malloc always returns payload pointers that are aligned to 8 bytes, your malloc implementation should do likewise and always return 8-byte aligned pointers.
• mm_free: The mm_free routine frees the block pointed to by ptr It returns nothing. This routine is only guaranteed to work when the passed pointer ( ptr ) was returned by an earlier call to mm_malloc or mm_realloc has not yet been freed.
• mm_realloc: The mm_realloc routine returns a point er to an allocated region of at least size bytes with the following constraints:
• if ptr is NULL, the call is equivalent to mm_malloc(size);
• if size is equal to zero, the call is equivalent to mm_free(ptr);
• if ptr is not NULL, it must have been returned by an earlier call to mm_malloc or mm_realloc . The call to mm_realloc changes the size of the memory block pointed to by ptr (the old block ) to size bytes and returns the address of the ne w block. Notice that the address of the new block might be the same as th e old block, or it might be different, depending on your implementation, the amount of internal fragmentation in the old block, and the size of the realloc request.
  The contents of the new block are the same as those of the old ptr block, up to the minimum of the old and new sizes. Everything else is uninitialized. For example, if the old block is 8 bytes and the new block is 12 bytes, then the first 8 bytes of the new block are identical to the first 8 bytes of the old block and the last 4 bytes are uninitialized. Similarly, if the old block is 8 bytes and the new block is 4 bytes, then the contents of the new block are identical to the first 4 bytes of the old block.
  These semantics must match the semantics of the corresponding libc malloc , realloc , and free routines. Type man malloc for complete documentation.