Dynamic Memory

Notes

• We will be using some c functions for this
  • They are routines for manipulating the heap directly, but that is messy
• void * malloc(size_t size)
  • Attempts to allocate size bytes on the heap
  • Returns the address if successful
  • returns null (0) if not.
• void free(void *ptr)
  • Returns the memory pointed to by pointer to the heap
• Both of these are partial truths, but they will do for us.
• These are lower level versions of new and delete in c++
• To use them we need

  
  extern malloc
  extern free

• The rest is simple
  • store the number of bytes you want in rdi
  • call malloc
  • rax will hold either 0 if the call failed or the address of memory
  • Address this memory as we have been.
• When you are finished
  • Store the address malloc returned in rdi
  • call free