How to align memory in Objective C?

Question

Apple recommends to have your data 16 byte aligned when you use Accelerate Framework. How do you do this in practice?

If I have an array int[10000];, is there a pragma? How do I align this to 16 byte?

Answer 1

In order to align data you need to use #pragma pack. To get 16 byte alignement you would need to use:

#pragma pack(push,16) ... your data structure here ... #pragma pack(pop)

I'd recommend you to read more about alignment, coz you may end up with corrupted data.

Answer 2

malloc and friends always have 16 byte alignment. Among other reasons to support vectors.

If you have an int array [10000]; then most likely it shouldn't be fixed size, and not on the stack, but allocated using malloc. And then it has 16 byte alignment.