Avoid exception handling loops if no handler is defined

emulator/src/runtime/exception.rs

@@ -3,7 +3,7 @@ use thiserror::Error;
 use super::memory::MemoryError;
 use crate::constants::Word;
 
-#[derive(Error, Debug)]
+#[derive(Error, Debug, Clone)]
 pub enum Exception {
     #[error("hardware interrupt")]
     HardwareInterrupt,

emulator/src/runtime/memory.rs

@@ -144,7 +144,7 @@ impl TryFrom<&Cell> for Address {
 }
 
 /// Represents errors related to memory manipulations
-#[derive(Debug, Error)]
+#[derive(Debug, Error, Clone, Copy)]
 pub enum MemoryError {
     /// The given address was invalid
     #[error("invalid address {0}")]

emulator/src/runtime/mod.rs

@@ -155,6 +155,16 @@ impl Computer {
         &mut self,
         exception: &Exception,
     ) -> std::result::Result<(), Exception> {
+        // We don't want to recover from the exception if there is no handler setup
+        let handler = self.memory.get(C::INTERRUPT_HANDLER)?;
+        if handler.extract_instruction().is_err() {
+            tracing::warn!(
+                "No exception handler at address 200 for exception {:?}",
+                exception
+            );
+            return Err(exception.clone());
+        }
+
         debug!(exception = %exception, "Recovering from exception");
         *(self.memory.get_mut(C::INTERRUPT_PC_SAVE)?) = self.registers.get(&Reg::PC);
         *(self.memory.get_mut(C::INTERRUPT_SR_SAVE)?) = self.registers.get(&Reg::SR);