emu86: unbounded e command doesn't work when no stdin is available

[hintron]

I'm trying to set up regression tests to run on the Git pre-commit hook. The problem is that the hook is not an interactive shell, so stdin is disabled/points to nothing. This messes up with the e command, though the e N command seems to work just fine. The symptoms of e are that nothing is printed to the debug terminal and the program hangs indefinitely.

[hintron]

In addition to replacing e with e N, it also seems to work if the pre-commit script re-introduces stdin like so

exec < /dev/tty

See https://stackoverflow.com/questions/3417896/how-do-i-prompt-the-user-from-within-a-commit-msg-hook.

[hintron]

SimControl.cpp:

void CSimControl::Execute(unsigned int repeatCount)
...
		if(ProgramWindow.KeyPress()) c = ProgramWindow.GetProgramInput();

Conio.cpp:

// Returns key if a key has been pressed and is waiting to be read.
bool keyPress(void)
{
	FD_SET(STDIN_FD, &stdin_wait_set);

	if(select(1, &stdin_wait_set, NULL, NULL, &tm_zero) > 0) return true;
	return false;
}

I need to debug to see what happens here when STDIN_FD is closed. But it seems like it's undefined behavior:

https://stackoverflow.com/questions/543541/what-does-select2-do-if-you-close2-a-file-descriptor-in-a-separate-thread

Perhaps I could add some kind of check that skips checking for input if stdin is closed

[hintron]

It looks like the problem is not that stdin is closed, but rather that it's set to /dev/null. When stdin is closed, e works just fine.

[hintron]

Here's a reproducer:

exec 0</dev/null
emu86 -c "l artoss.bin;simptris;e"

So the Git pre-commit hook must set stdin to /dev/null, which messes things up.

Closing stdin completely works fine:

exec 0<&-
emu86 -c "l artoss.bin;simptris;e"