Return codes for success and failure (int, bool)

[heinrich5991]

How do we want to communicate success and failure in the code base? According to #6429 (comment), we're currently using 0 as success and non-0 as failure for functions returning int. We use true as success and false as failure for functions returning bool.

These are currently opposites, and since you can't see (at a call site) whether a function returns int or bool, it seems error-prone to me. I think it'd make sense to unify this somehow. E.g. #6429 moves this towards true for success.

@Robyt3 argues that he finds if(function()) { /* success */ } more readable than if(function()) { /* failure */ }.

For functions returning different kinds of errors, it might make more sense to treat 0 as success because there's usually one success path but many failure paths. I'm not sure if we even use that in the code base. str_hex_decode returns multiple error codes, but I don't think they're used by any caller.

Prior art

curl uses 0 as success. zlib uses 0 as success. WINAPI mostly uses non-0 as success. I think most POSIX APIs that don't return a value use 0 as success.

[def-]

New functions should use bool return types in my opinion.

[heinrich5991]

Should they return true for success or failure?

[def-]

true for success of course.

[Learath2]

bool returns and true for success is what I'd also vote for. If we were sticking with C, I'd probably prefer int returns and 0 for success.

For functions returning different kinds of errors I'm honestly not sure how best to handle them, should they maybe be using enums for their return type? With an enum class we could maybe override the bool cast. if(!function()) { /* handle error */ } is a really pretty pattern so it's quite annoying that we can't have it for those kinds of functions unless we pick 0/false for success.

[Robyt3]

For enums I think both if(foo() != FOO_SUCCESS) { /* handle error */ } and if(foo() == FOO_SUCCESS) { /* handle success */ } are good patterns.

[edg-l]

true for success

bools to convey the meaning instead of int

[heinrich5991]

true for success.