Fix runtime cost ref.Val stack #517
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/assign @TristonianJones |
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Feedback applied @TristonianJones |
TristonianJones
requested changes
Mar 22, 2022
interpreter/runtimecost.go
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| // the stack. | ||
| // WARNING: It is possible for multiple expressions with the same ID to exist (due to how macros are implemented) so it's | ||
| // possible that a dropped ID will remain on the stack. They should be removed when IDs on the stack are popped. | ||
| func (s *refValStack) popArgs(args []Interpretable) ([]ref.Val, bool) { |
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nit: consider calling this dropArgs
TristonianJones
approved these changes
Mar 22, 2022
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I discovered that the stack that I had introduced in #494 as part of the introduction of runtime cost budgeting was not being managed correctly. Specifically, not all stack items pushed were being properly popped.
This PR fixes the stack by tracking the expression IDs associated with each stack value. The
popoperations then specify the expression IDs of the stack items they wish to pop. If any spurious values are above the stack item being popped, they are removed from the stack as part of thepop.This solves a bunch of problems and generally makes the stack much safer to use.
I have also improved the stack handling overall, which helps keep memory usage to a minimum. The only remaining case where I am certain that spurious stack items are left behind is the case where top-level variable lookup not being accounted for correctly.