3 ms·
Arenas are the simplest allocation scheme ever. // Start of frame void *arena = malloc(LOTS_OF_MEMORY); void *next_ptr = arena; // Allocate somethi
by loup-vaillant 8y ago
Arenas are the simplest allocation scheme ever.
// Start of frame
void *arena = malloc(LOTS_OF_MEMORY);
void *next_ptr = arena;
// Allocate something
object = *next_ptr; // return that value
next_ptr = object_size + alignment; // crash if out of memory
// End of frame
free(arena);
By the way, such "separate complex ad hoc" memory allocation schemes are the reason why manual memory management is faster than garbage collection. If you did everything with malloc(), it would be slower (unless the GC language allocates much more than C, which they often do).
- Keyframe 8y agoNo need to malloc each frame. Malloc at startup and memset each frame (don't even need to do that, tbh).
- maccard 8y agoNope, just set the pointer back to where it started from. You do need to be super careful doing this though, as anything that relies on RAII (in c++ land) will be busted. You could manually call the destructor on the object in that case, but kind of defeats the purpose of the "no allocation" goals
- geezerjay 8y agoC++ includes it's "placement new" feature specifically to cater to the memory pool needs. There's no allocation, and only constructor and destructor calls.
- tom_ 8y agoIt’s a good idea to have a mode that does malloc every frame, as that makes stale pointers much easier to find.