From 2b837cf6fbfb8b12421f33ca6fb43c3c776b7c65 Mon Sep 17 00:00:00 2001
From: ripsaw8080 <ripsaw8080@users.sourceforge.net>
Date: Wed, 22 Jun 2016 16:29:13 +0000
Subject: [PATCH] Correct stack pointer for COM format programs when there is
 less than 64K of memory available. Fixes Corncob 3D issue reported in bug
 #443.

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3988
---
 src/dos/dos_execute.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/dos/dos_execute.cpp b/src/dos/dos_execute.cpp
index 80faeb82..4b27cab0 100644
--- a/src/dos/dos_execute.cpp
+++ b/src/dos/dos_execute.cpp
@@ -419,8 +419,11 @@ bool DOS_Execute(char * name,PhysPt block_pt,Bit8u flags) {
 	RealPt csip,sssp;
 	if (iscom) {
 		csip=RealMake(pspseg,0x100);
-		sssp=RealMake(pspseg,0xfffe);
-		mem_writew(PhysMake(pspseg,0xfffe),0);
+		if (memsize<0x1000) {
+			LOG(LOG_EXEC,LOG_WARN)("COM format with only %X paragraphs available",memsize);
+			sssp=RealMake(pspseg,(memsize<<4)-2);
+		} else sssp=RealMake(pspseg,0xfffe);
+		mem_writew(Real2Phys(sssp),0);
 	} else {
 		csip=RealMake(loadseg+head.initCS,head.initIP);
 		sssp=RealMake(loadseg+head.initSS,head.initSP);