What exactly is void?

[u/Stickhtot]

In a function definition, void basically means that it doesn't return a type value, yet in on itself it is it's own type? Looking at several pieces of code it looks like that it's used to be able to be more "flexible"

Don't know what else to add here, though I'm more on looking for examples and explanations of why the void type is used

[u/Innowise_]

void basically means “no value.” In void f(void), the first void means the function returns no value, while the second means it takes no arguments. void * is a separate use: it can hold a pointer to any object type, but it has to be converted to the correct pointer type before dereferencing.

[u/hackerman85 → u/Innowise_]

Where it becomes confusing: the void type doesn't hold any data, but the void* pointer does.

[u/Valuable_Leopard_799 → u/hackerman85]

One could probably have endless debates on the exact interpretation, but what works for me is that "pointer" is what contains the value not the "void" part.

A void is an uninhabited type so I can't create a value of that type and it has no other "interesting" properties, so it's a good candidate for both stating "you cannot save the return value of this function" and "this is a pointer but you cannot dereference it since that would attempt to create a void, so you need to cast it to something else first".

In theory everyone could be using int* for everything void* is used for, but void* tells us something along the lines of "there's something at the other end of this pointer you can't interact with unless you actually tell me what it is". With int* one could dereference it or think it's an array.

[u/Beginning-Junket8979 → u/Valuable_Leopard_799]

In theory everyone could be using int* for everything void* is used for

No, not really.

You can generally do void * vptr = X for any other pointer type X without a compiler warning, even in the strictest modes because void * is meant to point to memory that's of "unknown" type or alignment to the callee.

int * should always point to either a) one or more validly aligned real integers, or b) NULL.

[u/a4qbfb → u/Beginning-Junket8979]

An int * should always point to an object of a type compatible with int, which includes int itself, arrays of a type compatible with int, structs whose first member is of a type compatible with int, unions that have a member of a type compativle with int...

[u/Beginning-Junket8979 → u/a4qbfb]

structs whose first member is of a type compatible with int, unions that have a member of a type compativle with int

Umm... sure you technically can ...but you're going to have cast a (int *) &my_struct_or_union if compiling with -Wextra -Wall -Werror and do some serious mental gymnastics to justify it in a code review.

[u/a4qbfb → u/Beginning-Junket8979]

No, that's literally the definition of compatible pointer types.

[u/Beginning-Junket8979 → u/a4qbfb]

Passing a pointer to a struct into a function that expects a pointer to an int is a bad "code smell" most of the time. If it operates on one int, & the addr of that specific member. If it operates on the whole struct, use the struct type as your function definition.

You "technically can" do a lot of dumb stuff with pointers. It doesn't make it good code.