DorisDuan06 / Memory-Allocation-Functions

Implemented malloc(), free(), realloc() and memcheck() in C.

Memory-Allocation-Functions

This project implememted malloc(), free(), realloc() and memcheck() in C.

In AVL.c, it takes the address, size of the allocated, freed or reallocated memories, creating/deleting nodes in a AVL tree or changing the node information.

In traverse.c, it has a traverse_xx() function for each memory allocation function (realloc537() uses traverse_free()) to go through each node in the AVL tree and check if a memory request is valid.

In 537malloc.c, it includes malloc537(), free537(), realloc537() and memcheck537() four functions. When they are called, they will call their relative traverse_xx() functions to go through the AVL tree and check validations. As for malloc537(), in addition to actually allocating the memory by calling malloc(), it will record the address and size for the memory that is allocated in the heap. It will get the starting address from the return value from malloc() and the size from the size parameter. It will check the size parameter for zero length and report as WARNINGS; For realloc537(), if ptr is NULL, then it follows the specification of malloc537() above. If size is zero and ptr is not NULL, then it follows the specification of free537() above. Otherwise, in addition to changing the memory allocation by calling realloc(), it will first check to see if address = ptr, and removes that node, then adds a new one where address is the return value from realloc() and size is the memory size; memcheck537() checks to see the address range specified by address ptr and length size are fully within a range allocated by malloc537() and memory not yet freed by free537(). When an error is detected, then print out a detailed and informative error message and exit the program (with a -1 status).

Different WARNINGS and ERRORS:

malloc537()

WARNINGS:

1. Allocate memory of zero length.

ERRORS:

1. malloc() failure.

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free537()

ERRORS:

1. Free memory that has not be allocated with malloc537().
2. Free memory that is not the first byte of the range of memory that was allocated.
3. Free memory that was previously freed (double free).

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realloc537()

WARNINGS:

1. Reallocate memory of zero length.

ERRORS:

(When need to free memory, same with free537())