WITH-HASH-TABLE-ITERATOR plays badly with closures

[rongarret]

? h
#<HASH-TABLE :TEST EQUAL size 3/60 #x3020010965ED>
? (with-hash-table-iterator (f h) (lambda () (multiple-value-list (f))))
#<COMPILED-LEXICAL-CLOSURE #x30200126EE0F>
? (funcall *)
> Error: value #<HASH-TABLE :TEST EQ size 3/60 #x302000C9D12D> is not of the expected type SIMPLE-VECTOR.

[rongarret]

Damn, forgot the curly braces. Really need a way to go back and edit these things.

? h
#<HASH-TABLE :TEST EQUAL size 3/60 #x3020010965ED>
? (with-hash-table-iterator (f h) (lambda () (multiple-value-list (f))))
#<COMPILED-LEXICAL-CLOSURE #x30200126EE0F>
? (funcall *)
> Error: value #<HASH-TABLE :TEST EQ size 3/60 #x302000C9D12D> is not of the expected type SIMPLE-VECTOR.

[gb]

The dictionary entry for WITH-HASH-TABLE-ITERATOR says:

"It is unspecified what happens if any of the implicit interior state of an iteration is returned outside the dynamic extent of the with-hash-table-iterator form such as by returning some closure over the invocation form."

In other words: F is allowed to refer to things that have dynamic extent (can be stack-allocated), and referring to those things after the body has exited has undefined results. (IIRC, the implicit internal state in question is represented as a stack-allocated SIMPLE-VECTOR, and the "undefined behavior" in this case has to do with the fact that there's something else where that stack-allocated vector used to be.)