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Old 12-13-2005, 12:02 AM   #1
Registered: Dec 2004
Location: India
Distribution: Fedora Core 4
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why warning is shown for exit()

When I use exit() function in loops I'm getting the warning

copy.c:13: warning: incompatible implicit declaration of built-in function ‘exit’

Why does this happen?
Old 12-13-2005, 12:20 AM   #2
Registered: Apr 2004
Location: India
Distribution: Ubuntu
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Not sure, being a newbie myself, but I think you have to declare the function before using it. Try int exit()

Edit: You are programming C, right?
Old 12-13-2005, 12:48 AM   #3
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Registered: Mar 2004
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#include <stdlib.h>

man 2 exit =>
_EXIT(2) Linux Programmer's Manual _EXIT(2)

_exit, _Exit - terminate the current process

#include <unistd.h>

void _exit(int status);

#include <stdlib.h>

void _Exit(int status);

The warning should go away if you #include <stdlib.h> (which, in turn, has the correct function prototype for "exit()").

Just FYI, you should *not* try to declare your own functions if there's a valid header available - ALWAYS try to use an existing header file FIRST.

I was recently using the binary of a product that was compiled under Linux 2.4 ... and WOULD NOT WORK under Linux 2.6 ... all because the programmer innocently coded "extern errno" instead of "#include <errno.h>".

Moral: If there's a header, use it. If you don't know what the header is, look it up ("man", MSDN DevHelp ... or even Google, if necessary).

Old 12-13-2005, 12:51 AM   #4
Registered: Apr 2004
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Thanks for the info, I'll keep that in mind


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