Strange assembly from array 0-initialization

Question

Inspired by the question Difference in initalizing and zeroing an array in c/c++ ?, I decided to actually examine the assembly of, in my case, an optimized release build for

Answer 1

The reason for lines 2 and 5 is because you specified a 0 in the array initializer. The compiler will initialize all constants then pad out the rest using memset. If you were to put two zeros in your initializer, you'd see it strw (word instead of byte) then memset 8 bytes.

As for the padding, it's only used to align memory accesses -- the data shouldn't be used under normal circumstances, so memsetting it is wasteful.

Edit: For the record, I may be wrong about the strw assumption above. 99% of my ARM experience is reversing code generated by GCC/LLVM on the iPhone, so my assumption may not carry over to MSVC.