kc3-lang/SDL

2021-06-12T14:55:24

OS2_GetDisplayModes: malloc a new copy of mode's driver data. Based on a patch by Jochen Schäfer <josch1710@live.de> : The problem is, that in the initialization code uses the same structure for desktop_mode and current_mode. See SDL_os2video.c:OS2_VideoInit(): stSDLDisplay.desktop_mode = stSDLDisplayMode; stSDLDisplay.current_mode = stSDLDisplayMode; ... stSDLDisplayMode.driverdata = pDisplayData; Then, if you call GetDisplayModes, current_mode will added to the modes list, with the same driverdata pointer to desktop_mode. SDL_AddDisplayMode( display, &display->current_mode ); When VideoQuit gets called, first the modes list gets freed including the driverdata, the desktop_mode gets freed. See SDL_video.c:SDL_VideoQuit(): for (j = display->num_display_modes; j--;) { SDL_free(display->display_modes[j].driverdata); display->display_modes[j].driverdata = NULL; } SDL_free(display->display_modes); display->display_modes = NULL; SDL_free(display->desktop_mode.driverdata); display->desktop_mode.driverdata = NULL; So, the display_modes[j].driverdata gets freed, but desktop_mode->driverdata points to the same memory, but is not NULL'ed. When desktop_mode->driverdata gets freed the memory is already freed, and libcx crashes the application on SDL_Quit.

diff --git a/src/video/os2/SDL_os2video.c b/src/video/os2/SDL_os2video.c
index 0ec0f1e..45f7b05 100644
--- a/src/video/os2/SDL_os2video.c
+++ b/src/video/os2/SDL_os2video.c
@@ -1562,8 +1562,14 @@ static int OS2_GetDisplayDPI(_THIS, SDL_VideoDisplay *display, float *ddpi,
 
 static void OS2_GetDisplayModes(_THIS, SDL_VideoDisplay *display)
 {
+    SDL_DisplayMode mode;
+
     debug_os2("Enter");
-    SDL_AddDisplayMode(display, &display->current_mode);
+    SDL_memcpy(&mode, &display->current_mode, sizeof(SDL_DisplayMode));
+    mode.driverdata = (MODEDATA *) SDL_malloc(sizeof(MODEDATA));
+    if (!mode.driverdata) return; /* yikes.. */
+    SDL_memcpy(mode.driverdata, display->current_mode.driverdata, sizeof(MODEDATA));
+    SDL_AddDisplayMode(display, &mode);
 }
 
 static int OS2_SetDisplayMode(_THIS, SDL_VideoDisplay *display,