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Ralph Hempel wrote: wrote:

I'm trying to replace the Lua default l_alloc function with my own one. My aim is to have all memory Lua allocates inside a single array of pre-allocated memory.


void* alloc_impl_manual( void* ptr, size_t osize, size_t nsize )
  if (nsize)
std::vector<unsigned char>* mem = new std::vector<unsigned char>(nsize);
               //yes, it will leak. don't care for now

return &(*mem)[0]; //returned memory position should be aligned by new
  return NULL;

Ummm, besides the leak, should you not be returning:

  return( mem )

since mem is already a pointer to the memory you allocated?

And this expression  &(*mem)[0] is very strange. I parse that as:
std::vector<int> v;
int* c_array = &v[0]; //not just &v !


printf( "%d%d", c_array[0], c_array[1] ); //"42"

The expression gives the position of the continuous memory regions hold by std::vector. mem would just be the this-pointer of the vector object and therefore the wrong thing. This is an stl feature to get backward compatibility to c-style arrays as shown in the little example above.

(the adress of ( (the contents of mem) ???? )

my compiler warns that the subscripted value is neither an array nor a


John had the right solution. I forgot to move the old mem to the new range in case of a re-allocation. Was my first allocator :)
Thank you all!