question about Function pointers Post: 302472135

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Top Forums Programming question about Function pointers Post 302472135 by Corona688 on Tuesday 16th of November 2010 11:01:38 AM

11-16-2010

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The syntax to use a function pointer is a little tricky, but the concept isn't hard at all if you know what a pointer is. It's just a pointer, that points to a function, because functions reside in memory too.

When you call a function name in C, what you're actually doing is calling an address in memory where the function's code resides. Most of the linker's job is to figure out where everything should go and substitute appropriate addresses for names. So, whenever you call a function, it actually ends up as a hardcoded address...

It's also possible to call an arbitrary address; for instance, if you loaded a dynamic library, you have to use function pointers to call functions from it since you won't know what they will be until the library's loaded. It works the same as far as the code's concerned. It just uses a pointer value you give it, instead of hardcoding one.

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LEARN ABOUT REDHAT

new_item

mitem_new(3X)															     mitem_new(3X)

NAME

       mitem_new - create and destroy menu items

SYNOPSIS

       #include <menu.h>
       ITEM *new_item(const char *name, const char *description);
       int free_item(ITEM *item);

DESCRIPTION

       The  function  new_item	allocates a new item and initializes it from the name and description pointers. Please notice that the item stores
       only the pointers to the name and description. Those pointers must be valid during the lifetime of the item. So you should be very carefull
       with names or descriptions allocated on the stack of some routines.
       The  function  free_item de-allocates an item. Please notice that it is the responsibility of the application to release the memory for the
       name or the description of the item.

RETURN VALUE

       The function new_item returns NULL on error.

       The function free_item returns one of the following:

       E_OK The routine succeeded.

       E_SYSTEM_ERROR
	    System error occurred (see errno).

       E_BAD_ARGUMENT
	    Routine detected an incorrect or out-of-range argument.

       E_CONNECTED
	    Item is connected to a menu.

SEE ALSO

       curses(3X), menu(3X).

NOTES

       The header file <menu.h> automatically includes the header file <curses.h>.

PORTABILITY

       These routines emulate the System V menu library.  They were not supported on Version 7 or BSD versions.

AUTHORS

       Juergen Pfeifer.  Manual pages and adaptation for new curses by Eric S. Raymond.

																     mitem_new(3X)