Disable FPE while initializing SDL2

See: PascalGameDevelopment/SDL2-for-Pascal#56
According to this GitHub Issue, when initializing the software renderer
on Linux, SDL2 triggers a crash in Mesa code. This happens because
FPC and Delphi enable FPE checking by default. This commit disables
those exceptions for the duration of SDL2 video initialization,
which should prevent crashes while using the software renderer.

Author: suve

src/ld25.pas

@@ -19,7 +19,8 @@
 {$INCLUDE defines.inc}
 
 uses
-	SysUtils, SDL2, SDL2_image, SDL2_mixer,
+	SysUtils, Math,
+	SDL2, SDL2_image, SDL2_mixer,
 	Assets, Colours, ConfigFiles, FloatingText, Fonts, Game, Images, Objects, MathUtils, Rooms, Shared
 ;
 
@@ -576,7 +577,10 @@
 
 Function Startup():Boolean;
 Var
-	Title, S:AnsiString; Timu:Comp; GM:TGameMode;
+	Title, ErrStr: AnsiString;
+	Timu: Comp;
+	GM: TGameMode;
+	OldMask, NewMask: TFPUExceptionMask;
 Begin
 	Timu:=GetMSecs(); Randomize();
 
@@ -585,7 +589,15 @@
 
 	LoadConfig();
 	For GM:=Low(GM) to High(GM) do SaveExists[GM]:=IHasGame(GM);
-	
+
+	// Disable Floating Poing Exception checking while initializing the video stack.
+	// See: https://github.com/PascalGameDevelopment/SDL2-for-Pascal/issues/56
+	OldMask := Math.GetExceptionMask();
+	NewMask := OldMask;
+	Include(NewMask, exInvalidOp);
+	Include(NewMask, exZeroDivide);
+	Math.SetExceptionMask(NewMask);
+
 	Write('Initializing SDL2 video... ');
 	If (SDL_Init(SDL_Init_Video or SDL_Init_Timer)<>0) then begin
 		Writeln('Failed!');
@@ -647,7 +659,10 @@
 		SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, 'nearest');
 		SDL_RenderSetLogicalSize(Shared.Renderer, RESOL_W, RESOL_H)
 	end;
-	
+
+	// Restore the old mask after we disabled FPE checks.
+	Math.SetExceptionMask(OldMask);
+
 	Write('Creating render target texture... ');
 	Shared.Display := SDL_CreateTexture(Shared.Renderer, SDL_GetWindowPixelFormat(Shared.Window), SDL_TEXTUREACCESS_TARGET, RESOL_W, RESOL_H);
 	if(Shared.Display = NIL) then begin
@@ -658,8 +673,8 @@
 
 	Write('Loading assets... ');
 	RegisterAllAssets();
-	If Not LoadAssets(S, @LoadUpdate) then begin
-		Writeln('ERROR'); Writeln(S); Exit(False);
+	If Not LoadAssets(ErrStr, @LoadUpdate) then begin
+		Writeln('ERROR'); Writeln(ErrStr); Exit(False);
 	end else
 		Writeln('Success!');