From ed199f38b4fa2fd69077341f41609b4a84aa9ade Mon Sep 17 00:00:00 2001
From: Walter van Niftrik
Date: Wed, 27 Jan 2010 13:14:28 +0000
Subject: SCI: Experimental fix for Longbow outlook crash. When using a pointer
 in number arithmetic, substitute a large value instead of 0 (cf. Hoyle hack
 in kAbs).

svn-id: r47597
---
 engines/sci/engine/vm.cpp | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

(limited to 'engines/sci')

diff --git a/engines/sci/engine/vm.cpp b/engines/sci/engine/vm.cpp
index 3d320d485c..e636935908 100644
--- a/engines/sci/engine/vm.cpp
+++ b/engines/sci/engine/vm.cpp
@@ -87,8 +87,10 @@ static StackPtr validate_stack_addr(EngineState *s, StackPtr sp) {
 
 static int validate_arithmetic(reg_t reg) {
 	if (reg.segment) {
+		// When using a pointer in number arithmetic, we substitute a large value as
+		// some scripts rely on this (cf. Hoyle hack in kAbs).
 		warning("[VM] Attempt to read arithmetic value from non-zero segment [%04x]", reg.segment);
-		return 0;
+		return 0x3e9;
 	}
 
 	return reg.offset;
@@ -97,7 +99,7 @@ static int validate_arithmetic(reg_t reg) {
 static int signed_validate_arithmetic(reg_t reg) {
 	if (reg.segment) {
 		warning("[VM] Attempt to read arithmetic value from non-zero segment [%04x]", reg.segment);
-		return 0;
+		return 0x3e9;
 	}
 
 	if (reg.offset & 0x8000)
@@ -890,25 +892,37 @@ void run_vm(EngineState *s, int restoring) {
 		case 0x13: // ugt?
 			s->r_prev = s->r_acc;
 			r_temp = POP32();
-			s->r_acc = make_reg(0, (r_temp.segment == s->r_acc.segment) && r_temp.offset > s->r_acc.offset);
+			if (r_temp.segment && s->r_acc.segment)
+				s->r_acc = make_reg(0, (r_temp.segment == s->r_acc.segment) && r_temp.offset > s->r_acc.offset);
+			else
+				s->r_acc = ACC_ARITHMETIC_L(validate_arithmetic(r_temp) > /*acc*/);
 			break;
 
 		case 0x14: // uge?
 			s->r_prev = s->r_acc;
 			r_temp = POP32();
-			s->r_acc = make_reg(0, (r_temp.segment == s->r_acc.segment) && r_temp.offset >= s->r_acc.offset);
+			if (r_temp.segment && s->r_acc.segment)
+				s->r_acc = make_reg(0, (r_temp.segment == s->r_acc.segment) && r_temp.offset >= s->r_acc.offset);
+			else
+				s->r_acc = ACC_ARITHMETIC_L(validate_arithmetic(r_temp) >= /*acc*/);
 			break;
 
 		case 0x15: // ult?
 			s->r_prev = s->r_acc;
 			r_temp = POP32();
-			s->r_acc = make_reg(0, (r_temp.segment == s->r_acc.segment) && r_temp.offset < s->r_acc.offset);
+			if (r_temp.segment && s->r_acc.segment)
+				s->r_acc = make_reg(0, (r_temp.segment == s->r_acc.segment) && r_temp.offset < s->r_acc.offset);
+			else
+				s->r_acc = ACC_ARITHMETIC_L(validate_arithmetic(r_temp) < /*acc*/);
 			break;
 
 		case 0x16: // ule?
 			s->r_prev = s->r_acc;
 			r_temp = POP32();
-			s->r_acc = make_reg(0, (r_temp.segment == s->r_acc.segment) && r_temp.offset <= s->r_acc.offset);
+			if (r_temp.segment && s->r_acc.segment)
+				s->r_acc = make_reg(0, (r_temp.segment == s->r_acc.segment) && r_temp.offset <= s->r_acc.offset);
+			else
+				s->r_acc = ACC_ARITHMETIC_L(validate_arithmetic(r_temp) <= /*acc*/);
 			break;
 
 		case 0x17: // bt
-- 
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