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Comment by quelsolaar | Hacker News Reader

I'm a member of the C standard group and i strongly opposed defer. It creates an invisible jump, at the point of the execution. Its essentially a "comefrom" statement, a structure that was created as a joke trying to find something worse than goto. I'm much rather have people use goto. At least you can see where the goto statement is and find the label where it is going.

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er... okay... can't this be said for... literally any abstraction in C? a function which does not return a value which has no return statement has a ... invisible jump. A for loop, while loop, if statement... all have "invisible" jumps... Would you rather C had a conditional statement which could only take a single instruction or a goto? Why not just have an assembly language? Having a defer statement which queues up blocks of code for execution at the end of a scope seems far far cleaner than the extremely error-prone goto cleanup style (or any non-goto alternative for it). Yes the jumps are implicit but it's not exactly that difficult to figure out what gets jumped to and when... at least unless you have really excessively long functions in which case everything becomes hard to track (including those "invisible jumps" in for loops, while loops and if statements).

That sounds like a serious misunderstanding of the common use case to me. Have people on the C committee never understood the value of RAII in C++? It’s such a huge safety improvement for ensuring that, for example, a mutex is unlocked — or a file closed — on early return.

The problem with RAII is that unlike defer it requires you to have an exception mechanism. RAII and Exceptions are completely interdependant and you can't use one without the other (you're basically guaranteed leaks if you use exceptions without RAII and to implement RAII you need exceptions).

It's valuable but let's not confuse it with defer which allows a great deal of safety without requiring exceptions.

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