From fa9d26d34db98c483e0ef10209356b3ed22254a9 Mon Sep 17 00:00:00 2001
From: Nathaniel Walizer <robots.are.love@gmail.com>
Date: Mon, 6 Jan 2025 22:14:21 -0800
Subject: [PATCH] Add raw instruction debug output; add option to ignore
 illegal instructions

---
 e6502.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/e6502.c b/e6502.c
index 28e49bb..f467261 100644
--- a/e6502.c
+++ b/e6502.c
@@ -515,7 +515,9 @@ static inline void sbc(e6502_Core *core, e6502_Address adr) {
 
 static inline void inc(e6502_Core *core, e6502_Address adr) {
     // TODO: Emulate double-read or double-write
-    uint8_t val = e6502_adr_r8(core, adr) + 1;
+    uint8_t val = e6502_adr_r8(core, adr);
+    e6502_adr_w8(core, adr, val);
+    val += 1;
     core->registers.P &= ~(e6502_Status_Z | e6502_Status_N);
     core->registers.P |= (val & e6502_Status_N);
     if (!val) core->registers.P |= e6502_Status_Z;
@@ -869,7 +871,7 @@ static const e6502_Instruction e6502_instructions[256] = {
 
 };
 
-/*
+#ifdef E6502_DEBUG
 int e6502_instr_size(uint8_t opcode) {
     const e6502_Instruction* instr = &e6502_instructions[opcode];
     if (    instr->address == adr_imp ||
@@ -884,7 +886,7 @@ int e6502_instr_size(uint8_t opcode) {
     }
 }
 
-int e6502_dump_instr(e6502_Core* core, e6502_Mem_Addr addr,
+void e6502_dump_instr(e6502_Core* core, e6502_Mem_Addr addr,
                      FILE* file) {
     uint8_t opcode = e6502_r8(core, addr);
     int size = e6502_instr_size(opcode);
@@ -894,11 +896,9 @@ int e6502_dump_instr(e6502_Core* core, e6502_Mem_Addr addr,
     } else if (size == 3) {
         fprintf(file, " $%04x", e6502_r16(core, addr + 1));
     }
-    fputc('\n', file);
+//    fputc('\n', file);
 }
-*/
 
-#ifdef E6502_DEBUG
 void e6502_dump_regs(e6502_Core* core, FILE* file) {
     fprintf(file, "S:%02x A:%02x X:%02x Y:%02x P:%02x\n",
             core->registers.S, core->registers.A,
@@ -938,9 +938,14 @@ int e6502_step(e6502_Core* core) {
             &e6502_instructions[opcode];
     if (!instr->operator) {
 #ifdef E6502_DEBUG
-        fprintf(stdout, "$%04x: $%02x\n", last_pc, opcode);
+        fprintf(stdout, "$%04x: $%02x -> ILLEGAL\n", last_pc, opcode);
 #endif
+#ifndef E6502_ILLEGAL
         core->cycle = -1;
+#else
+        core->registers.PC++;
+        core->cycle += 1;
+#endif
 
     } else {
         core->registers.PC++;
@@ -954,6 +959,8 @@ int e6502_step(e6502_Core* core) {
         }
         e6502_dump_regs(core, stdout);
         fprintf(stdout, "$%04x: ", last_pc);
+        e6502_dump_instr(core, last_pc, stdout);
+        fputs(" -> ", stdout);
         e6502_fprintf_instr(stdout, opcode, (uint8_t*)&val);
         fputc('\n', stdout);
 #endif