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0 pointsint_19h5y ago0 comments

> defer also cannot handle resources whose lifetimes do not correspond to nested scopes

It can, it's just more explicit about it. In a language with destructors, you'd do RAII here by having a list destructor that cleans up each element in turn. In a language with defer, the same destructor becomes a regular function that you'd invoke in the deferred expression.

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3 comments · 1 top-level

edflsafoiewq5y ago· 2 in thread

The issue is with the individual elements, which get pushed to the list, popped off the list, moved around, pushed to a different list, etc.

The other issue is since there is no generic notion of a destructor, it isn't possible to write generic functions that destroy elements. If you call, say, replace_range on a list of strings, it will leak the replaced strings.

int_19hOP5y ago

> The issue is with the individual elements, which get pushed to the list, popped off the list, moved around, pushed to a different list, etc.

That's separate from the destructor for the entire list. It does mean that the code that removes an element from the list has to explicitly invoke the destructor for it - which is in agreement with using "defer" to explicitly invoking destructors for locals.

> The other issue is since there is no generic notion of a destructor, it isn't possible to write generic functions that destroy elements.

But you can have a generic notion of a destructor - that's orthogonal to whether destructors are invoked explicitly. You just have an interface (or trait, or whatever it's called) that exposes a destructor method for a type.

edflsafoiewq5y ago

You could but Zig does not.

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