From d6088005ef565b4c42de2f822186bdcfe22e9ed8 Mon Sep 17 00:00:00 2001 From: Adam Joseph Date: Thu, 13 Oct 2022 21:11:41 -0700 Subject: docs(tvix/eval) vm: explain VM::{frames,stack,with_stack} Signed-off-by: Adam Joseph Change-Id: I94ba31ae25c1ff744f929a722c76a0c33cc361ff Reviewed-on: https://cl.tvl.fyi/c/depot/+/7016 Reviewed-by: tazjin Tested-by: BuildkiteCI --- tvix/eval/src/vm.rs | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/tvix/eval/src/vm.rs b/tvix/eval/src/vm.rs index e1f9d3096b89..52de99f490ed 100644 --- a/tvix/eval/src/vm.rs +++ b/tvix/eval/src/vm.rs @@ -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, + + /// 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 rather than as + /// Vec> or a Vec inside CallFrame for + /// efficiency reasons: it avoids having to allocate a Vec on + /// the heap each time a CallFrame is entered. stack: Vec, - /// 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, /// Runtime warnings collected during evaluation. -- cgit 1.4.1