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Comment by chacham15 | Hacker News Reader

I think you're missing the point here, the conversion function is trivially inlinable:

    char* sds_cstr(sds *str){
        return &str[0]; //you could probably just cast too
    }

The other posters solution is actually not equivalent in this way (his sds is convertable to char* instead of sds*).

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Even an inlined function only has value if our goal is to open the door to implementation changes in the future. But because the current implementation is zero-cost (an inlined no-op), any behavioral change will necessary compromise performance.

Otherwise (if we want to retain the zero-cost guarantee of converting to a C string), directly accessing the member variable is: functionally equivalent, simpler, more concise, more readable, more explicit.

I actually prefer the inline function here (while making the member char* private when compiling as C++), since that mostly prevents assignment to the member variable in settings where that would not be a valid operation.

With that said, I agree that the additional verbosity is a significant drawback, and I can understand going with the slightly-less-safe option for that reason alone.

Ah, that’s a good point. I’m a fan of extra safety, though we’d need to make a few extra changes to get around C’s lack of private variables: We could make the internal member instead a size_t, and cast to pointer form when needed inside the library or when converting via this inline function (which is still a no-op in terms of performance). The only major downside then remaining is perhaps syntax/verbosity, which IMO is secondary to safety.

However: If we open the discussion up to C++, then this is pretty easy to solve without any real syntactic or performance compromise: we can make a class/struct which defines implicit conversions to C strings, and disables any implicit conversions from C strings.

Good point about implicit conversions; I may actually be able to use that to clean up some code in the near future.

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