two fixes for issue 6793

code/fireball/fireballs.cpp

@@ -920,19 +920,7 @@ int fireball_create(vec3d *pos, int fireball_type, int render_type, int parent_o
 		return -1;
 	}
 
-
-	if (!Unused_fireball_indices.empty()) {
-		n = Unused_fireball_indices.back();
-		Unused_fireball_indices.pop_back();
-	}
-	else {
-		n = static_cast<int>(Fireballs.size());
-		Fireballs.emplace_back();
-	}
-
-	fireball* new_fireball = &Fireballs[n];
-
-	// get an lod to use	
+	// get an lod to use
 	fb_lod = fireball_get_lod(pos, fd, size);
 
 	// change lod if low res is desired
@@ -947,8 +935,21 @@ int fireball_create(vec3d *pos, int fireball_type, int render_type, int parent_o
 	}
 	fl = &fd->lod[fb_lod];
 
-	new_fireball->lod = (char)fb_lod;
+	// don't create a fireball without usable graphics
+	if (fl->bitmap_id < 0 || fl->fps <= 0 || fl->num_frames <= 0) {
+		return -1;
+	}
+
+	if (!Unused_fireball_indices.empty()) {
+		n = Unused_fireball_indices.back();
+		Unused_fireball_indices.pop_back();
+	} else {
+		n = sz2i(Fireballs.size());
+		Fireballs.emplace_back();
+	}
+	auto new_fireball = &Fireballs[n];
 
+	new_fireball->lod = (char)fb_lod;
 	new_fireball->flags = extra_flags;
 	new_fireball->warp_open_sound_index = warp_open_sound;
 	new_fireball->warp_close_sound_index = warp_close_sound;

code/osapi/dialogs.cpp

@@ -238,22 +238,23 @@ namespace os
 
 			gr_activate(0);
 
-			int buttonId;
+			int buttonId = -1;	// if dialog is silently suppressed
 			if (SDL_ShowMessageBox(&boxData, &buttonId) < 0)
 			{
 				// Call failed
-				buttonId = 1; // No action
+				buttonId = 1;
 			}
 
 			switch (buttonId)
 			{
-			case 2:
+			case 2:				// Exit
 				abort();
 
-			case 0:
+			case 0:				// Debug
 				Int3();
 				break;
 
+			case 1:				// Continue
 			default:
 				break;
 			}
@@ -283,6 +284,12 @@ namespace os
 		{
 			mprintf(("\n%s\n", text));
 
+			// also output to stderr so the message is visible if the dialog is suppressed
+			// (e.g., the SDL message box is dismissed silently by the window manager when the
+			// game is fullscreen on Linux)
+			fprintf(stderr, "\n%s\n", text);
+			fflush(stderr);
+
 			if (running_unittests) {
 				throw ErrorException(text);
 			}
@@ -322,21 +329,22 @@ namespace os
 
 			gr_activate(0);
 
-			int buttonId;
+			int buttonId = -1;	// if dialog is silently suppressed
 			if (SDL_ShowMessageBox(&boxData, &buttonId) < 0)
 			{
 				// Call failed
-				abort();
+				buttonId = 1;
 			}
 
 			switch (buttonId)
 			{
-			case 1:
-				abort();
-
-			default:
+			case 0:				// Debug
 				Int3();
 				break;
+
+			case 1:				// Exit
+			default:
+				abort();
 			}
 			gr_activate(1);
 		}
@@ -349,6 +357,12 @@ namespace os
 			// output to the debug log before anything else (so that we have a complete record)
 			mprintf(("WARNING: \"%s\" at %s:%d\n", text.c_str(), filename, line));
 
+			// also output to stderr so the message is visible if the dialog is suppressed
+			// (e.g., the SDL message box is dismissed silently by the window manager when the
+			// game is fullscreen on Linux)
+			fprintf(stderr, "WARNING: \"%s\" at %s:%d\n", text.c_str(), filename, line);
+			fflush(stderr);
+
 			if (running_unittests) {
 				throw WarningException(text);
 			}
@@ -390,22 +404,23 @@ namespace os
 
 			gr_activate(0);
 
-			int buttonId;
+			int buttonId = -1;	// if dialog is silently suppressed
 			if (SDL_ShowMessageBox(&boxData, &buttonId) < 0)
 			{
 				// Call failed
-				buttonId = 1; // No action
+				buttonId = 1;
 			}
 
 			switch (buttonId)
 			{
-			case 2:
+			case 2:				// Exit
 				abort();
 
-			case 0:
+			case 0:				// Debug
 				Int3();
 				break;
 
+			case 1:				// Continue
 			default:
 				break;
 			}