From bc9888c9b552cbd7f138ad36e743dab80e67f523 Mon Sep 17 00:00:00 2001 From: Ozkan Sezer Date: Sat, 12 Jun 2021 14:55:24 +0300 Subject: [PATCH] OS2_GetDisplayModes: malloc a new copy of mode's driver data. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Based on a patch by Jochen Schäfer : 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. --- src/video/os2/SDL_os2video.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/src/video/os2/SDL_os2video.c b/src/video/os2/SDL_os2video.c index 0ec0f1e61..45f7b05c5 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,