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Full Discussion: Ignoring the stdio.h file in a C file
Top Forums Programming Ignoring the stdio.h file in a C file Post 302737033 by Corona688 on Wednesday 28th of November 2012 10:08:38 AM
Old 11-28-2012
In C++, this is explicitly an error. No undefined functions allowed, period.

C on the other hand, will assume undefined functions take integers and return integers. int printf(int); This works okay-ish if your function takes nothing but 32-bit sized types -- a reasonable guess on a 32-bit system, potentially disastrous anywhere else. If you tried to declare a FILE * or anything else which really needs stdio.h, it would fail to compile.

On 64-bit, your program will segfault due to the 64-bit pointer being mangled through a 32-bit type. The compiler will warn you, too, though the error is less than obvious -- "truncation from assigned type" or some such, rather than the kind of message you'd expect, "you're putting the wrong type into an undefined function and it will blow up in your face".

In short, don't do that. I've seen lots of code blow up when ported to 64-bit because people didn't bother including something they needed.
Last edited by Corona688; 11-28-2012 at 11:30 AM..
 

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LEARN ABOUT OPENSOLARIS

atomic_set_long_excl

atomic_bits(9F) 					   Kernel Functions for Drivers 					   atomic_bits(9F)

NAME

       atomic_bits, atomic_set_long_excl, atomic_clear_long_excl - atomic set and clear bit operations

SYNOPSIS

       #include <sys/atomic.h>

       int atomic_set_long_excl(volatile ulong_t *target, uint_t bit);

       int atomic_clear_long_excl(volatile ulong_t *target, uint_t bit);

DESCRIPTION

       The  atomic_set_long_excl()  and  atomic_clear_long_excl()  functions perform an exclusive atomic bit set or clear operation on target. The
       value of bit specifies the number of the bit to be modified within target. Bits are numbered from zero to one less than the maximum  number
       of bits in a long. If the value of bit falls outside of this range, the result of the operation is undefined.

RETURN VALUES

       The  atomic_set_long_excl()  and  atomic_clear_long_excl() functions return 0 if bit was successfully set or cleared. They return -1 if bit
       was already set or cleared.

ERRORS

       No errors are defined.

CONTEXT

       These functions can be called from user, interrupt, or kernel context.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       atomic_add(9F),	atomic_and(9F),  atomic_cas(9F),   atomic_dec(9F),   atomic_inc(9F),   atomic_or(9F),	atomic_swap(9F),   membar_ops(9F),
       attributes(5), atomic_ops(3C)

SunOS 5.11							    16 Jan 2006 						   atomic_bits(9F)
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