Help with installing system

Help with installing system

Jason Marmon

Member #14,859

January 2013

I'm trying to install the system in order to use timers in my program, but I'm unsure of what the second argument is. According to the documentation, this is the function:
[code]
al_install_system(version, (*atexit_ptr)(void (*)(void)
[/code]
I know the first argument should be ALLEGRO_VERSION_INT, but what does (*atexit_ptr)(void (*)(void) even mean??

Thomas Fjellstrom

Member #476

June 2000

Its the crazy syntax used to declare pointers to functions.

In this case you can use NULL or atexit (which is a libc function).

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

Jason Marmon

Member #14,859

January 2013

oops, wrong code tags, sorry bout that
and thanks for the reply, NULL worked

Trent Gamblin

Member #261

April 2000

I'd be careful with that. I did that once and on Windows when the program exited, if it was using ALLEGRO_FULLSCREEN_WINDOW the taskbar would be gone. It's a caveat in the A5 Windows port.

EDIT: I mean using NULL. Using atexit is fine.

Jason Marmon

Member #14,859

January 2013

in that case, would you mind explaining how to use atexit? I'm not quite sure how to implement it

Thomas Fjellstrom

Member #476

June 2000

using the function name without the brackets or arguments will evaluate to the function's address. That is, its exactly what al_install_system wants, a function pointer.

Phrasz

Member #10,091

August 2008

You can always look at the basics:
http://www.maths.cam.ac.uk/undergrad/catam/ccatsl/manual/node50.html

(and then follow up with his link on pointer arguments)

Aikei_c

Member #14,871

January 2013

It's strange that nobody else mentioned that, but why don't you just use al_init()?

Jason Marmon

Member #14,859

January 2013

Weird, I have that in the code already...I didn't know al_init() also installs the system.