From 07fb107e2d0527545bcdbb47ace80551702a71b1 Mon Sep 17 00:00:00 2001
From: Ben Bridle <ben@derelict.engineering>
Date: Mon, 16 Dec 2024 13:42:21 +1300
Subject: Fix reported address of debug instruction in debug output

Because the program counter is incremented immediately after an
instruction byte is loaded, the value of the program counter reported
by a debug instruction was actually the address of the following byte.
This made the SYM symbol name line in the debug output report the wrong
symbol name in some situations.

This was fixed by decrementing the value used.
---
 src/debug.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(limited to 'src/debug.rs')

diff --git a/src/debug.rs b/src/debug.rs
index 17ed604..c01ee15 100644
--- a/src/debug.rs
+++ b/src/debug.rs
@@ -36,8 +36,9 @@ impl DebugState {
 
     pub fn debug_summary(&mut self, core: &BedrockCore) {
         if self.enabled {
+            let prev_pc = core.mem.pc.wrapping_sub(1);
             eprintln!("\n PC: 0x{:04x}   Cycles: {} (+{} in {:.2?})",
-                core.mem.pc, core.cycle,
+                prev_pc, core.cycle,
                 core.cycle.saturating_sub(self.last_cycle),
                 self.last_mark.elapsed(),
             );
@@ -46,7 +47,7 @@ impl DebugState {
             eprint!("RST: ");
             debug_stack(&core.rst, 0x10);
             // Print information about the closest symbol.
-            if let Some(symbol) = self.symbols.for_address(core.mem.pc) {
+            if let Some(symbol) = self.symbols.for_address(prev_pc) {
                 let name = &symbol.name;
                 let address = &symbol.address;
                 eprint!("SYM: {BLUE}@{name}{NORMAL} 0x{address:04x}");
-- 
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