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docs(tvix/eval) vm: explain VM::{frames,stack,with_stack}

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Signed-off-by: Adam Joseph <adam@westernsemico.com>
Change-Id: I94ba31ae25c1ff744f929a722c76a0c33cc361ff
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7016
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
This commit is contained in:
Adam Joseph 2022-10-13 21:11:41 -07:00 committed by clbot
parent ad71fdaa75
commit d6088005ef
1 changed files with 12 additions and 2 deletions
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14
tvix/eval/src/vm.rs
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@ -38,11 +38,21 @@ impl CallFrame {
}
pub struct VM<'o> {
/// The VM call stack. One element is pushed onto this stack
/// each time a function is called or a thunk is forced.
frames: Vec<CallFrame>,
/// The VM value stack. This is actually a "stack of stacks",
/// with one stack-of-Values for each CallFrame in frames. This
/// is represented as a Vec<Value> rather than as
/// Vec<Vec<Value>> or a Vec<Value> inside CallFrame for
/// efficiency reasons: it avoids having to allocate a Vec on
/// the heap each time a CallFrame is entered.
stack: Vec<Value>,
/// Stack indices of attribute sets from which variables should be
/// dynamically resolved (`with`).
/// Stack indices (absolute indexes into `stack`) of attribute
/// sets from which variables should be dynamically resolved
/// (`with`).
with_stack: Vec<usize>,
/// Runtime warnings collected during evaluation.