Reworked Pierre's patch a little bit, which added SDL_WaitEventTimeout()
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Description From Philipp 2009-01-16 20:50:01 (-) [reply]
The File test/README from the svn says this:
testgl A very simple example of using OpenGL with SDL
testgl2 Improved version of testgl
It is actually exchanged.
testgl.c is the improved version right now and testgl2.c the simple one.
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From: John Bartholomew
Subject: [SDL] SDL Semaphore implementation broken on Windows?
Hi,
Over the past couple of days, I've been battling with SDL, SDL_Mixer and SMPEG to try to find an audio hang bug. I believe I've found the problem, which I think is a race condition inside SDL's semaphore implementation (at least the Windows implementation). The semaphore code uses Windows' built in semaphore functions, but it also maintains a separate count value. This count value is updated with bare increment and decrement operations in SemPost and SemWaitTimeout - no locking primitives to protect them.
In tracking down the apparent audio bug, I found that at some point a semaphore's count value was being decremented to -1, which is clearly not a valid value for it to take.
I'm still not certain exactly what sequence of operations is occuring for this to happen, but I believe that overall it's a race condition between a thread calling SemPost (which increments the count) and the thread on the other end calling SemWait (which decrements it).
I will try to make a test case to verify this, but I'm not sure if I'll be able to (threading errors being difficult to reproduce even in the best circumstances).
However, assuming this is the cause of my problems, there is a very
simple fix:
Windows provides InterlockedIncrement() and InterlockedDecrement()
functions to perform increments and decrements which are guaranteed to be atomic. So the fix is in thread/win32/SDL_syssem.c: replace occurrences of --sem->count with InterlockedDecrement(&sem->count); and replace occurrences of ++sem->count with InterlockedIncrement(&sem->count);
This is using SDL v1.2.12, built with VC++ 2008 Express, running on a
Core 2 duo processor.
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Description From Michael Stone 2008-09-25 19:27:29 (-) [reply]
To determine whether a pid is occupied with the kill(pid, 0) idiom, you have to
test
#include <signal.h>
#include <errno.h>
kill(pid, 0) < 0 && errno == ESRCH
not just
#include <signal.h>
kill(pid, 0) < 0
otherwise you get incorrect results when pid is running as a different user
(causing kill(pid, 0) to return -1 + EPERM).
src/audio/alsa/SDL_alsa_audio.c is certainly affected by this bug in both
1.2.13 and 1.3-trunk. It probably occurs in other places as well.
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Description From esigra 2008-01-07 16:20:21 (-) [reply]
I try to get a clean compile for a project using SDL. But I get warnings
from SDL headers when I use -Wold-style-cast. This is especially bad
because I plan to build the software with -Werror=old-style-cast when we
have switched over to GCC 4.2, which has that option.
But this problem can be fixed in the SDL headers. I checked out the SVN
version and made some patches. See the attached patch.
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Make sure OpenGL library is loaded before working with OpenGL windows,
even those created with SDL_CreateWindowFrom()
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When creating a texture from a surface, synchronize the texture with the surface.
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First attempt at replacing MakeSubSurface for pre 1.2.0 ==> Scaling not yet working
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#ifndef SDL_VIDEO_DRIVER_X11_DYNAMIC_XSS
#define SDL_VIDEO_DRIVER_X11_DYNAMIC_XSS NULL
#endif
so that the X code would compile. It looked like it was needed
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Instead of the GNOME screensaver respecting the MIT-SCREEN-SAVER extension
and registering for the screensaver idle event, it uses a completely different
control mechanism. Our alternatives are to use dbus (very complicated) or
this really painful hack.
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The screensaver is disabled by default when using SDL 1.2 compatibility.
Use the new XScreenSaver extension, removed unused DPMS extension.
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