Is it safe to read to memory after it has been allocated with `pureMalloc` and `pureRealloc`?

[rempas via Digitalmars-d-learn]

In other terms, do these functions auto-initialize memory to be 
ready for use? I test it out using `printf` to print a string. 
"%s" expects for a null terminated string and it seems to work so 
I suppose that these functions auto-initialize the bytes to `\0`.

However, memory is tricky and I still don't know how memory (and 
virtual memory) works under the hood so it may just randomly work 
and it may give me a segmentation fault at some point.

Does anyone knows what's going on here?