HowTo Tell if your SDL application is hung for "mysterious" VT reasons

[twobob]

Is your SDL app just stopped producing video? no obvious reason?

check your strace log

ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
2686 write(1, "V_InitMode: using 8 bit video mo"..., 35) = 35
2686 ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
2686 write(1, "I_SetRes: Using resolution 592x8"..., 35) = 35
2686 ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
2686 ioctl(4, VT_GETSTATE, 0xbe9f9a5c) = 0
2686 ioctl(4, VT_ACTIVATE, 0x1) = 0
2686 ioctl(4, VT_WAITACTIVE, 0x1) = ?

if you have it hanging like this? it appears to be something to do with not handling signals gracefully on exit. It's an artefact of no proper event handling within the parent application, leaving SDL in an interim state.

Best bet is to simply shutdown -r now. SDL will now work again.

To actually fix the issue more permanently:

If signal handler for eg. SIGTERM signal is installed that looks like this:

void sigproc (int sig);

void sigproc (int sig)
{
SDL_Quit();
exit(1);
}

int main ()
{
..
signal(SIGTERM, sigproc);
..
}

Then killing a SDL app with "kill -15 AppPid" gracefully terminates the app, and subsequent invocations of the SDL app succeed.

Spoiler:

Whilst researching this (thinly documented) issue I happened across a LOVELY wordwar between two devs.

the critic doesn't like if( and if ( being in the same code stanza
the coder is deep-diving age old VT and tty code and couldnt give a monkeys about the critics opinion.

The old wars are the best. Style V Content. Ding Ding round 1.
http://old.nabble.com/-PATCH--vt:-ad...d24304586.html

[hawhill]

Errm, it rather looks like it is waiting for a Virtual Terminal. That's a quite common patch for SDL, disabling interaction with a controlling terminal (because there might be none). There seem to be more involved, look at this: http://stackoverflow.com/questions/3...minal-on-linux

Using "kill -9" (SIGKILL) should also get rid of the process, I think, without installing any other signal handlers within the application.