C++

22.4    “void” Pointers

The third function, gzwrite(), takes two parameters: a void* to the data and the length of the data. The return value is the amount of data written; a value of zero indicates an error.

But what exactly is void*? Did you notice that our own write() function, using the as_bytes function, created a span<byte> whose data() method returns a const byte*, which I then passed to the void* of gzwrite()? Normally, C++ always complains when you take a variable of one type and try to use it as something else. Imagine if gzwrite() took an int: then the const byte* from write wouldn't fit, and I would have had to define the parameter differently—or use a trick. And what if the data to be written are int* data or double*? Do you then ...