From d2dcd96ce186e6038273f93ecc1d8b70e32768b7 Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Sun, 29 Mar 2020 22:13:54 -0400
Subject: [PATCH] emul: add useful emul_trace() debugging tool

---
 emul/emul.c | 10 ++++++++++
 emul/emul.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/emul/emul.c b/emul/emul.c
index 9cd45c3..a636816 100644
--- a/emul/emul.c
+++ b/emul/emul.c
@@ -7,6 +7,7 @@ They all run on the same kind of virtual machine: A z80 CPU, 64K of RAM/ROM.
 #include "emul.h"
 
 static Machine m;
+static ushort traceval = 0;
 
 static uint8_t io_read(int unused, uint16_t addr)
 {
@@ -92,6 +93,15 @@ void emul_loop()
     while (emul_step());
 }
 
+void emul_trace(ushort addr)
+{
+    ushort newval = m.mem[addr+1] << 8 | m.mem[addr];
+    if (newval != traceval) {
+        traceval = newval;
+        fprintf(stderr, "trace: %04x PC: %04x\n", traceval, m.cpu.PC);
+    }
+}
+
 void emul_printdebug()
 {
     fprintf(stderr, "Min SP: %04x\n", m.minsp);
diff --git a/emul/emul.h b/emul/emul.h
index 174bdf5..9d848fe 100644
--- a/emul/emul.h
+++ b/emul/emul.h
@@ -30,4 +30,5 @@ Machine* emul_init();
 bool emul_step();
 bool emul_steps(unsigned int steps);
 void emul_loop();
+void emul_trace(ushort addr);
 void emul_printdebug();