[spacechild1]

Pre- and postconditions are actually part of the function signature, i.e. they are visible to the caller. For example, static analyzers could detect contract violations just by looking at the callsite, without needing access to the actual function implementation. The pre- and postconditions can also be shown in IDE tooltips. You can't do this with your own contracts implementation.

Finally, it certainly helps to have a standardized mechanisms instead of everyone rolling their own, especially with multiple libraries.

[kevin_thibedeau]

Is a pointer parameter an input, output, or both?

[drfloyd51]

Input.

You are passing in a memory location that can be read or written too.

That’s it.

[72deluxe]

In terms of contract in a function, you might be passing the pointer to the function so that the function can write to the provided pointer address. Input/output isn't specifying calling convention (there's fastcall for that) - it is specifying the intent of the function. Otherwise every single parameter to a function would be an input because the function takes it and uses it...

I worked on a massive codebase where we used Microsoft SAL to annotate all parameters to specify intent. The compiler could throw errors based on these annotations to indicate misuse.

This seems like an extension of that.

[drfloyd51]

Annotation sounds good. (As long as it is enforced or honored.) which is the best you can do in C++.

A language like C# has true directional parameters. C only truly has “input”

[kevin_thibedeau]

A pointer doesn't necessarily point to memory.

[j1elo]

A nitpick to your nitpick: they said "memory location". And yes, a pointer always points to a memory location. Notwithstanding that each particular region of memory locations could be mapped either to real physical memory or any other assortment of hardware.

[peterfirefly]

No. Neither in the language (NULL exists) nor necessarily on real CPUs.

[bluGill]

NULL exists on real CPUs. Maybe you meant nullptr which is a very different thing, don't confuse the two.

[kevin_thibedeau]

You can point to a register which is certainly not memory.