Glulx doesn't work without the Inform library?

Authoring Inform 6
,
1

I compiled the basic Hello World program from DM4 chapter 1.2 in Inform 6 targeting Glulx:

!  "Hello world" example program
[ Main;
  print "Hello world^";
];

It compiles without errors but the program doesn’t work in any interpreters I have on Mac. Both Zoom and Inform 7’s built-in interpreter show a gray screen without any output, and Quixe crashes on startup with a “Quixe init: glk_put_jstring: invalid stream” error message.

Just wanted to confirm that this is expected (some Glulx initialization stuff is necessary that the Inform library would do) and not an interpreter issue?

2

This seems vaguely similar to a problem that I suspected was in the compiler, library, or interpreter. It turned out to be a very longstanding bug in the Frotz core. I’ll poke at this one from a few different angles.

3

That is as expected. When a Glulx interpreter starts up, it won’t have any I/O system selected, so there’s no way for it to generate any output that you would see. The usual sequence would be something like:

  1. Set Glk as the I/O system with something like “@setiosys 2 0;”.
  2. Create a Glk text buffer window to be the main window.
  3. Set the main window’s stream as the default stream.
  4. Now you can call “print” and have something appear.

Have a look at “GGInitialise()” in parserm.h in Inform library 6/11 or later to see an example of this.

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4

The minimum you need is the following:

[ Main win;
	@setiosys 2 0; ! select Glk I/O system
	win = glk($0023, 0, 0, 0, 3, 0); ! glk_window_open
	glk($002F, win); ! glk_set_window
];

For example: https://github.com/erkyrath/glk-dev/blob/master/unittests/arraylimittest.inf

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5

Ok, that’s understandable although a bit unfortunate that literally the first thing that DM4 tells you to do can fail so subtly.

6

To be fair, the DM4 was written almost entirely before Glulx. I think it might be only mentioned once. To compile to Glulx you need the -G switch which the DM4 doesn’t even list as an option!

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