Track dbg! calls

Author: m-kus

Cargo.toml

@@ -15,6 +15,7 @@ default = ["elements"]
 elements = ["dep:elements", "bitcoin"]
 test-utils = ["simplicity-sys/test-utils"]
 serde = ["dep:serde", "bitcoin/serde", "elements/serde"]
+debug = []
 
 [lib]
 name = "simplicity"

src/bit_machine/mod.rs

@@ -347,11 +347,23 @@ impl BitMachine {
                     call_stack.push(CallStack::Goto(left));
                 }
                 node::Inner::Case(..) | node::Inner::AssertL(..) | node::Inner::AssertR(..) => {
-                    let choice_bit = self.read[self.read.len() - 1].peek_bit(&self.data);
+                    let in_frame = &self.read[self.read.len() - 1];
+                    let choice_bit: bool = in_frame.peek_bit(&self.data);
 
                     let (sum_a_b, _c) = ip.arrow().source.as_product().unwrap();
                     let (a, b) = sum_a_b.as_sum().unwrap();
 
+                    #[cfg(feature = "debug")]
+                    if let node::Inner::AssertL(_, cmr) = ip.inner() {
+                        let mut bits = in_frame.as_bit_iter(&self.data);
+                        // Skips 1 + max(a.bit_width, b.bit_width) - a.bit_width
+                        bits.nth(a.pad_left(b))
+                            .expect("AssertL: unexpected end of frame");
+                        let value = Value::from_padded_bits(&mut bits, _c)
+                            .expect("AssertL: decode `C` value");
+                        tracker.track_dbg_call(cmr, value);
+                    }
+
                     match (ip.inner(), choice_bit) {
                         (node::Inner::Case(_, right), true)
                         | (node::Inner::AssertR(_, right), true) => {
@@ -545,6 +557,9 @@ pub trait ExecTracker<J: Jet> {
         output_buffer: &[UWORD],
         success: bool,
     );
+
+    /// Track the potential execution of a `dbg!` call with the given `cmr` and `value`.
+    fn track_dbg_call(&mut self, cmr: &Cmr, value: Value);
 }
 
 /// Tracker of executed left and right branches for each case node.
@@ -580,6 +595,8 @@ impl<J: Jet> ExecTracker<J> for SetTracker {
     }
 
     fn track_jet_call(&mut self, _: &J, _: &[UWORD], _: &[UWORD], _: bool) {}
+
+    fn track_dbg_call(&mut self, _: &Cmr, _: Value) {}
 }
 
 impl<J: Jet> ExecTracker<J> for NoTracker {
@@ -588,6 +605,8 @@ impl<J: Jet> ExecTracker<J> for NoTracker {
     fn track_right(&mut self, _: Ihr) {}
 
     fn track_jet_call(&mut self, _: &J, _: &[UWORD], _: &[UWORD], _: bool) {}
+
+    fn track_dbg_call(&mut self, _: &Cmr, _: Value) {}
 }
 
 /// Errors related to simplicity Execution