How does .data? directive work under the hood

[hutch--]

 :bg

Do yourself a favour with uninitialised memory, DON'T assume it will be zero filled if its not in the spec for the OS, Compiler, Assembler or Linker or you could be unpleasantly surprised. If you need zero filled uninitialised data, zero fill it yourself. If its enough to worry about, use dynamic memory, its easier to deal with and you can deallocate it when you are finished with it.

[jj2007]

Do yourself a favour with uninitialised memory, DON'T assume it will be zero filled if its not in the spec for the OS, Compiler, Assembler or Linker

None of them is involved, it's the OS loader that takes care of the bss segment. It is really difficult to find documentation, but for Win32 you can assume that .data? gets filled with VirtualAlloc. Zeros, not garbage.