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Fix for double free when quitting on iOS

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Tim Angus 2012-02-20 09:40:35 PST

As alluded to in the email thread "SDL2 error on iOS (doublefree)", I believe
the original cause of this bug is confusion over the purpose of
SDL_VideoDisplay::current_mode. It looks as though it is a weak reference to
another mode, albeit with value semantics. The iOS port treated it as a strong
reference however and claimed ownership, which is why things blew up. All the
patch really does it to stop treating current_mode as a strong reference.

To prevent this happening again it might be an idea to change current_mode to
be a pointer type rather than a value. This would certainly make its semantics
much more obvious. Failing that, a comment in the struct indicating its weak
reference properties might be wise.
This commit is contained in:
Sam Lantinga 2012-02-20 20:46:30 -05:00
parent f7b34c87f6
commit d2a506d0d6
2 changed files with 51 additions and 51 deletions
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100
src/video/uikit/SDL_uikitvideo.m
View File

@ -121,14 +121,11 @@ The main screen should list a AxB mode for portrait orientation, and then
*/
static int
UIKit_AddSingleDisplayMode(SDL_VideoDisplay * display, int w, int h,
UIKit_AllocateDisplayModeData(SDL_DisplayMode * mode,
UIScreenMode * uiscreenmode, CGFloat scale)
{
SDL_DisplayMode mode;
SDL_zero(mode);
SDL_DisplayModeData *data = NULL;
if (uiscreenmode != nil) {
/* Allocate the display mode data */
data = (SDL_DisplayModeData *) SDL_malloc(sizeof(*data));
@ -138,24 +135,56 @@ UIKit_AddSingleDisplayMode(SDL_VideoDisplay * display, int w, int h,
}
data->uiscreenmode = uiscreenmode;
[data->uiscreenmode retain];
data->scale = scale;
}
mode->driverdata = data;
return 0;
}
static void
UIKit_FreeDisplayModeData(SDL_DisplayMode * mode)
{
if (!SDL_UIKit_supports_multiple_displays) {
// Not on at least iPhoneOS 3.2 (versions prior to iPad).
SDL_assert(mode->driverdata == NULL);
} else if (mode->driverdata != NULL) {
SDL_DisplayModeData *data = (SDL_DisplayModeData *)mode->driverdata;
[data->uiscreenmode release];
SDL_free(data);
mode->driverdata = NULL;
}
}
static int
UIKit_AddSingleDisplayMode(SDL_VideoDisplay * display, int w, int h,
UIScreenMode * uiscreenmode, CGFloat scale)
{
SDL_DisplayMode mode;
SDL_zero(mode);
mode.format = SDL_PIXELFORMAT_ABGR8888;
mode.refresh_rate = 0;
mode.driverdata = data;
if (UIKit_AllocateDisplayModeData(&mode, uiscreenmode, scale) < 0) {
return -1;
}
mode.w = w;
mode.h = h;
if (SDL_AddDisplayMode(display, &mode)) {
if (uiscreenmode != nil) {
[uiscreenmode retain];
}
return 0;
}
SDL_free(data);
// Failure case; free resources
SDL_DisplayModeData *data = (SDL_DisplayModeData *) mode.driverdata;
if (data != NULL) {
[data->uiscreenmode release];
SDL_free(data);
}
return -1;
}
@ -237,39 +266,27 @@ UIKit_AddDisplay(UIScreen *uiscreen, CGSize size)
mode.w = (int)(size.width * scale);
mode.h = (int)(size.height * scale);
mode.refresh_rate = 0;
UIScreenMode * uiscreenmode = nil;
// UIScreenMode showed up in 3.2 (the iPad and later). We're
// misusing this supports_multiple_displays flag here for that.
if (SDL_UIKit_supports_multiple_displays) {
SDL_DisplayModeData *data;
/* Allocate the mode data */
data = (SDL_DisplayModeData *) SDL_malloc(sizeof(*data));
if (!data) {
SDL_OutOfMemory();
return -1;
}
data->uiscreenmode = [uiscreen currentMode];
[data->uiscreenmode retain]; // once for the desktop_mode
[data->uiscreenmode retain]; // once for the current_mode
data->scale = scale;
mode.driverdata = data;
uiscreenmode = [uiscreen currentMode];
}
if (UIKit_AllocateDisplayModeData(&mode, uiscreenmode, scale) < 0) {
return -1;
}
SDL_zero(display);
display.desktop_mode = mode;
display.current_mode = mode;
SDL_DisplayData *data;
/* Allocate the display data */
data = (SDL_DisplayData *) SDL_malloc(sizeof(*data));
SDL_DisplayData *data = (SDL_DisplayData *) SDL_malloc(sizeof(*data));
if (!data) {
SDL_free(mode.driverdata);
SDL_OutOfMemory();
UIKit_FreeDisplayModeData(&display.desktop_mode);
return -1;
}
@ -341,20 +358,6 @@ UIKit_SetDisplayMode(_THIS, SDL_VideoDisplay * display, SDL_DisplayMode * mode)
return 0;
}
static void
UIKit_ReleaseUIScreenMode(SDL_DisplayMode * mode)
{
if (!SDL_UIKit_supports_multiple_displays) {
// Not on at least iPhoneOS 3.2 (versions prior to iPad).
SDL_assert(mode->driverdata == NULL);
} else {
SDL_DisplayModeData *data = (SDL_DisplayModeData *)mode->driverdata;
[data->uiscreenmode release];
SDL_free(data);
mode->driverdata = NULL;
}
}
void
UIKit_VideoQuit(_THIS)
{
@ -366,11 +369,10 @@ UIKit_VideoQuit(_THIS)
[data->uiscreen release];
SDL_free(data);
display->driverdata = NULL;
UIKit_ReleaseUIScreenMode(&display->desktop_mode);
UIKit_ReleaseUIScreenMode(&display->current_mode);
UIKit_FreeDisplayModeData(&display->desktop_mode);
for (j = 0; j < display->num_display_modes; j++) {
SDL_DisplayMode *mode = &display->display_modes[j];
UIKit_ReleaseUIScreenMode(mode);
UIKit_FreeDisplayModeData(mode);
}
}
}

2
src/video/uikit/SDL_uikitwindow.m
View File

@ -180,9 +180,7 @@ UIKit_CreateWindow(_THIS, SDL_Window *window)
// desktop_mode doesn't change here (the higher level will
// use it to set all the screens back to their defaults
// upon window destruction, SDL_Quit(), etc.
[((UIScreenMode *) display->current_mode.driverdata) release];
display->current_mode = *bestmode;
[((UIScreenMode *) display->current_mode.driverdata) retain];
}
}
}