From d1b556c5c56a79487209a304733628e53db6d56a Mon Sep 17 00:00:00 2001
From: David Schmidt <1110325+david-schmidt@users.noreply.github.com>
Date: Wed, 19 Aug 2020 15:24:31 -0400
Subject: [PATCH] Fix from Kent Dickey on the WAI instruction

Fantavision hangs when it starts on KEGS-based emulators (which includes GSport and GSplus) due to a bug in the way KEGS handles the WAI instruction.  Fantavision masks interrupts with SEI, sets a SHR line interrupt, and then does a WAI instruction.  This hangs KEGS since it expects an actual interrupt to end the WAI, but there won't be one since interrupts are masked.  I never realized this was a valid WAI use case.

The fix is easy.  In `instable.h`, change:
```
instcb_SYM              /*  WAI */
        g_wait_pending = 1;
        CYCLES_FINISH
```
(There may be some stale #ifdef ASM code, just ignore that) to:
```
instcb_SYM              /*  WAI */
        if(g_irq_pending) {
                g_wait_pending = 0;
                INC_KPC_1;
        } else {
                g_wait_pending = 1;
        }
```
Kent
---
 src/instable.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/instable.h b/src/instable.h
index d78db63..3f9a835 100644
--- a/src/instable.h
+++ b/src/instable.h
@@ -1,6 +1,6 @@
 /*
  GSport - an Apple //gs Emulator
- Copyright (C) 2010 by GSport contributors
+ Copyright (C) 2010 - 2020 by GSport contributors
  
  Based on the KEGS emulator written by and Copyright (C) 2003 Kent Dickey
 
@@ -2231,8 +2231,12 @@ instcb_SYM		/*  WAI */
 	b	dispatch
 	stw	scratch2,r%g_wait_pending(scratch1)
 #else
-	g_wait_pending = 1;
-	CYCLES_FINISH
+	if(g_irq_pending) {
+		g_wait_pending = 0;
+		INC_KPC_1;
+	} else {
+		g_wait_pending = 1;
+	}
 #endif
 
 instcc_SYM		/*  CPY abs */