Realloc Function Dont Work Correct

Hi all,

I want to use Dynamic Memory Allocation Functions.
My platform is NXP LPC1768 (Cortex M3).
My Heap Size Defined as 4096 Bytes in lpc17xx_startup.s file.

First of all, I allocate an area with malloc and this operation is success.
After that, I want to resize this area with realloc but system allocate area from Global Area(in my opinion, allocated area address is in the Global Area Range).
So it changes a my Global variable.

My Simple Code :

PRIVATE List *list;
PRIVATE U32 totalHeapSize;

int main()
{
      reallocDyncArea(10, (void**)&list);       // Will Be Success
      reallocDyncArea(20, 10, (void**)&list);   // Allocate From Global Area
}


PUBLIC RESULT allocDyncArea(U16 size, void** allocatedArea)
{
        RESULT retVal = (SUCCESS);

        if ((totalHeapSize + size) < (TOTAL_HEAP_SIZE / 2))
        {
                *allocatedArea = malloc(size);
                if (*allocatedArea == NULL)
                {
                        retVal = (FAILURE);
                }
                else
                {
                        totalHeapSize += size;
                        retVal = (SUCCESS);
                }
        }

        return (retVal);
}
PUBLIC RESULT reallocDyncArea(U16 newSize, U32 oldSize, void** reAllocatedArea)
{
        RESULT retVal = (SUCCESS);

        if ((totalHeapSize + newSize - oldSize) < (TOTAL_HEAP_SIZE / 2))
        {
                *reAllocatedArea = realloc(*reAllocatedArea, newSize);
                if (*reAllocatedArea == NULL)
                {
                        retVal = (FAILURE);
                }
                else
                {
                        totalHeapSize += (newSize - oldSize);
                        retVal = (SUCCESS);
                }
        }

        return (retVal);
}

I cant find problem.
What is my problem.

Thanks.

Murat