- It turns out that the Visual C++ 2005 runtime calls IsDebuggerPresent, which

is not available under Windows 95. Since this is (or at least should be) the
  only thing preventing us from running under Windows 95, I added a stub that
  replaces __imp__IsDebuggerPresent@0 with a pointer to a function that checks
  for the real thing.


SVN r279 (trunk)

Makefile.mingw

@@ -61,7 +61,8 @@ endif
 SRCS = $(CSRCS) $(CPPSRCS) $(ASRCS)
 CPPOBJFILES = $(notdir $(CPPSRCS:%.cpp=%.o))
 COBJFILES = $(notdir $(CSRCS:%.c=%.o))
-AOBJFILES = $(notdir $(ASRCS:%.nas=%.o))
+# win32/wrappers.nas should be built *only* for Visual C++ 2005 to enable execution on Windows 95
+AOBJFILES = $(filter-out %/wrappers.o,$(notdir $(ASRCS:%.nas=%.o)))
 RCOBJFILES = $(notdir $(RCSRCS:%.rc=%.o))
 
 COBJS = $(addprefix $(OBJDIR)/,$(CPPOBJFILES) $(COBJFILES) $(RCOBJFILES))

docs/rh-log.txt

@@ -1,3 +1,10 @@
+August 1, 2006
+- It turns out that the Visual C++ 2005 runtime calls IsDebuggerPresent, which
+  is not available under Windows 95. Since this is (or at least should be) the
+  only thing preventing us from running under Windows 95, I added a stub that
+  replaces __imp__IsDebuggerPresent@0 with a pointer to a function that checks
+  for the real thing.
+
 August 1, 2006 (Changes by Graf Zahl)
 - Fixed: The pickup message for Hexen's fighter's axe was assigned to the
   AxePuff, not the weapon itself.

src/thingdef.cpp

@@ -2491,8 +2491,6 @@ static void ActorActiveSound (AActor *defaults, Baggage &bag)
 //==========================================================================
 static void ActorDropItem (AActor *defaults, Baggage &bag)
 {
-	bool res;
-
 	// create a linked list of dropitems
 	if (!bag.DropItemSet)
 	{

src/win32/i_main.cpp

@@ -91,8 +91,6 @@ DWORD			MainThreadID;
 
 HMODULE			hwtsapi32;		// handle to wtsapi32.dll
 
-BOOL			(*pIsDebuggerPresent)(VOID);
-
 extern UINT TimerPeriod;
 extern HCURSOR TheArrowCursor, TheInvisibleCursor;
 
@@ -218,10 +216,6 @@ void DoMain (HINSTANCE hInstance)
 		// Since we need to remain binary compatible with older versions of Windows, we
 		// need to extract the ProcessIdToSessionId function from kernel32.dll manually.
 		HMODULE kernel = GetModuleHandle ("kernel32.dll");
-		if (kernel != 0)
-		{
-			pIsDebuggerPresent = (BOOL(*)())GetProcAddress (kernel, "IsDebuggerPresent");
-		}
 
 		// NASM does not support creating writeable code sections (even though this
 		// is a perfectly valid configuration for Microsoft's COFF format), so I

src/win32/wrappers.nas

@@ -0,0 +1,39 @@
+; The Visual C++ CRT unconditionally links to IsDebuggerPresent.
+; This function is not available under Windows 95, so here is a
+; lowlevel replacement for it.
+
+extern __imp__GetModuleHandleA@4
+extern __imp__GetProcAddress@8
+
+	SECTION .data
+
+global __imp__IsDebuggerPresent@0
+__imp__IsDebuggerPresent@0:
+	dd	IsDebuggerPresent_Check
+
+	SECTION	.rdata
+
+StrKERNEL32:
+	db "KERNEL32",0
+
+StrIsDebuggerPresent:
+	db "IsDebuggerPresent",0
+
+	SECTION .text
+
+IsDebuggerPresent_No:
+	xor		eax,eax
+	ret
+
+IsDebuggerPresent_Check:
+	push	StrKERNEL32
+	call	[__imp__GetModuleHandleA@4]
+	push	StrIsDebuggerPresent
+	push	eax
+	call	[__imp__GetProcAddress@8]
+	test	eax,eax
+	jne		near .itis
+	mov		eax,IsDebuggerPresent_No
+.itis
+	mov		[__imp__IsDebuggerPresent@0],eax
+	jmp		eax

zdoom.vcproj

@@ -106,6 +106,7 @@
 				TerminalServerAware="2"
 				OptimizeReferences="2"
 				EnableCOMDATFolding="2"
+				SetChecksum="true"
 			/>
 			<Tool
 				Name="VCALinkTool"
@@ -5371,6 +5372,46 @@
 					/>
 				</FileConfiguration>
 			</File>
+			<File
+				RelativePath=".\src\win32\wrappers.nas"
+				>
+				<FileConfiguration
+					Name="Release|Win32"
+					>
+					<Tool
+						Name="VCCustomBuildTool"
+						Description="Assembling $(InputPath)..."
+						CommandLine="nasmw -o &quot;$(IntDir)\$(InputName).obj&quot; -d OBJ_FORMAT_win32 -f win32 &quot;$(InputPath)&quot;"
+						Outputs="$(IntDir)\$(InputName).obj"
+					/>
+				</FileConfiguration>
+				<FileConfiguration
+					Name="Release|x64"
+					ExcludedFromBuild="true"
+					>
+					<Tool
+						Name="VCCustomBuildTool"
+					/>
+				</FileConfiguration>
+				<FileConfiguration
+					Name="Debug|Win32"
+					>
+					<Tool
+						Name="VCCustomBuildTool"
+						Description="Assembling $(InputPath)..."
+						CommandLine="nasmw -o &quot;$(IntDir)\$(InputName).obj&quot; -d OBJ_FORMAT_win32 -f win32 &quot;$(InputPath)&quot;"
+						Outputs="$(IntDir)\$(InputName).obj"
+					/>
+				</FileConfiguration>
+				<FileConfiguration
+					Name="Debug|x64"
+					ExcludedFromBuild="true"
+					>
+					<Tool
+						Name="VCCustomBuildTool"
+					/>
+				</FileConfiguration>
+			</File>
 		</Filter>
 		<Filter
 			Name="Shared Game"