uswitch(2)uswitch(2)NAMEuswitch - Get or set compatibility environment specific behavior for a
calling process through the uswitch value.
SYNOPSIS
#include <sys/uswitch.h>
long uswitch(
long cmd,
long mask );
PARAMETERS
Specifies the requested actions. The valid cmd values are: Returns the
current uswitch value for the calling process. If mask is non-zero, it
returns the status of specific uswitchbit-mask(s). Changes the cur‐
rent uswitch value for the calling process as specified by the mask
bit-mask(s). The following bit-masks are valid when specified with
either of the values for the cmd parameter: Specifies System V NULL
pointer behavior. Specifies process requests enhanced core file nam‐
ing.
DESCRIPTION
The uswitch system call is used to get or change the compatibility
environment specific behavior in Tru64 UNIX. Any changes affect the
calling process and its children.
When the USW_NULLP bit of uswitch is set to 1, the System V method of
treating NULL pointers is applied. In this method, references to a NULL
pointer always returns zero (0). When this bit-mask is reset to zero
(0), subsequent references to a NULL pointer generate a segmentation
violation signal (SIGSEGV).
When the USW_CORE bit of uswitch is set to 1, the process requests
enhanced core file naming. The bit-mask, when set, can be inherited
when the process forks. The bit-mask is cleared when an exec system
call is executed. See core(4) for more information about core files.
Any write(2) references to NULL pointers generate a segmentation viola‐
tion signal (SIGSEGV) regardless of the uswitch value.
NOTES
Usage of this system call may make the application non-portable.
RETURN VALUES
Upon successful completion, either the current or new uswitch value for
mask is returned. Otherwise, a value of -1 is returned and errno is
set to indicate the error.
ERRORS
If the uswitch system call fails, the uswitch value remains unchanged
and errno is set to the following: The mask is greater than USW_MAX or
less than USW_MIN.
EXAMPLES
The following code sample sets the bit mask for System V NULL pointer
behavior:
long uswitch_val;
... uswitch_val = uswitch(USC_GET,0); /* Gets current
value*/ uswitch(USC_SET, uswitch_val | USW_NULLP); /* Sets
USW_NULLP bit */ The following code sample sets the bit mask for
enhanced core file names:
long uswitch_val;
... uswitch_val = uswitch(USC_GET,0); /* Gets current
value*/ uswitch(USC_SET, uswitch_val | USW_CORE); /* Sets
USW_CORE bit */
uswitch(2)
