DllStructCreate initialization of memory

[SteveJM]

When I use DllStructCreate() to reserve a chunk of memory I would like to know if I can rely on that memory being initialized to zero. Experience suggests that it is, but I have been searching to try and find a definitive statement anywhere that this is the case. I apologise if I have missed somewhere. Part of the reason for this question is so that my next search (after my personal memory has dimmed) should yield a link to this post, hopefully with an answer.

A number of DLLs I use have structs where a few parts have to be explicitly set and other parts are reserved with the instruction that they must be set to zero. Because DllStructCreate() appears to zero-initialise the memory, I tend to forget to do it explicitly and everything seems to work. I am wondering whether I have been lucky and am storing up trouble for myself. It seems likely that the OS has been asked for zeroed memory, but without a promise in the documentation for DllStructCreate(),  perhaps that could change? Perhaps the developers wish to reserve the right to change their minds?