I was looking at atexit() and saw it takes a function pointer to a function with no return value or parameters. If I wanted to use this to clean up memory I allocated or save any data( like saving highscores to a file for a game ) in some variable, could I do it without the use of global variables?
Note : Assume I would only register the function after I checked everything is in working order.
> could I do it without the use of global variables?
No.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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That's too bad. Oh, well, I figured that was the answer, I just wasn't sure if there was a fancy way to get around it. I do have a follow up question though, when I run this codeOriginally Posted by Salem
then it pauses for a while when I press the [x] button before exiting from main. What is the reason for that pause, and does it have to wait for main() to complete before exiting the program?Code:#include <stdio.h> #include <stdlib.h> #include <windows.h> void func( ) { fprintf(stdout, "Yay!\n"); getchar(); return; } int main( ) { if ( atexit(func) ) return 1; Sleep(1000); return 0; }
Last edited by HelpfulPerson; 08-03-2013 at 03:37 PM.
The pause is from Sleep.
If I exited during some operations in main without the Sleep() function, would it call the function immediately with no pause then?
You can always return from main before Sleep is executed, if that's what you mean. The trouble is Sleep has probably executed by the time you exited the console.
Sleep function (Windows)This function causes a thread to relinquish the remainder of its time slice and become unrunnable for an interval based on the value of dwMilliseconds [the argument].
If it's unrunnable, anything the user does won't be processed for a while.
I think you are letting go of your original question too easily.
Yes, it's necessary to use a global variable (or worse) to pass data to an atexit() function, but can you think of any way this situation might be improved? You can't eliminate the global variable but you can certainly do better than a random mish-mash of global variables for all the various atexit() functions you want to register. Can you propose a more structured solution to the problem?
Code://try //{ if (a) do { f( b); } while(1); else do { f(!b); } while(1); //}
What I would likely do is store the needed data either in a global structure or in a global array. Then I would only copy data from the main program to that global variable when needed, instead of using it throughout the program.
you give up too easily. Salem was being only partially serious.
A good way to do this might be to have your "global" data marked as static in one of your source files, and have that same source file contain the functions to read and write that global data. static objects at the global scope are only visible within the source file in which they are declared, so it's not actually global, and won't have potential conflicts with other global data, and writing functions to access the data, instead of manipulating it directly, is always a good idea.
What can this strange device be?
When I touch it, it gives forth a sound
It's got wires that vibrate and give music
What can this thing be that I found?
