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The Question is: I have problems using RTL functions in a C++ program using IEEE floats. The following program will not run: #include <stdio.h> #include <lib$routines.h> #pragma nomember_alignment main() float f1 = 1.0; lib$wait(&f1); I compile it with the following commands: $ cxx/float=IEEE_FLOAT example.cxx $ cxxlink example.cxx When I run the program it crashes. I hope you can help me out. The Answer is :
Arguably far easier and far simpler than this current approach will
be a call to the C library sleep routine.
As for this problem, the "seconds" argument for the OpenVMS Run-time
library (RTL) routine lib$wait is interpreted as F_floating floating
point data type -- please see the extract from the HELP text attached
below for argument information.
The run-time error:
%SYSTEM-F-HPARITH, high performance arithmetic trap, Imask=00000000,
Fmask=00000400, summary=02, PC=FFFFFFFF80489C24, PS=0000001B
-SYSTEM-F-FLTINV, floating invalid operation, PC=FFFFFFFF80489C24,
PS=0000001B
indicates that the IEEE floating point format "1.0" is an invalid
bit pattern for the F_floating floating point data format.
If you wish to use the lib$wait call in a module that is compiled
with the IEEE floating point format (/FLOAT=IEEE_FLOAT), you will
need to perform an explicit floating point conversion. For example,
you could convert the floating point value or you could ask the
lib$wait call to appropriately interprete the floating point value:
#include <cvt$routines.h>
#include <cvtdef>
#include <lib$routines.h>
#include <libwaitdef.h>
#include <ssdef.h>
#include <stdio.h>
#include <stsdef.h>
main()
{
float ieee_s = 1.0;
int vax_f;
int RetStat;
int float_type = LIB$K_IEEE_S;
RetStat = cvt$ftof(&ieee_s,CVT$K_IEEE_S,&vax_f,CVT$K_VAX_F,0);
if (!$VMS_STATUS_SUCCESS( RetStat ))
return RetStat;
RetStat = lib$wait(&vax_f);
if (!$VMS_STATUS_SUCCESS( RetStat ))
return RetStat;
RetStat = lib$wait(&ieee_s, 0, &float_type);
if (!$VMS_STATUS_SUCCESS( RetStat ))
return RetStat;
return SS$_NORMAL;
}
Use of correctly-aligned data is strongly recommended for
reasons of performance -- the #pragma nomember_alignment
call should only be used when you must explicitly support
unaligned data references. Since there is no reason in
this example not to use aligned data, the pragma has been
removed. (Please see the OpenVMS FAQ for further details.)
The inclusion of explicit return status checks are strongly
recommended. Failure to perform such checks is a common
source of run-time problems -- often, obscure run-time
problems. Please see topic (1661) for other common run-time
coding problems.
Available information on the RTL call and on the return
HPARITH status code:
$ HELP RTL LIB$ LIB$WAIT
RTL_ROUTINES
LIB$
LIB$WAIT
Arguments
seconds
OpenVMS usage:floating_point
type: F_floating
access: read only
mechanism: by reference
The number of seconds to wait. The seconds argument contains the
address of an F-floating number that is this number.
The value is rounded to the nearest hundredth-second before use.
Seconds must be between 0.0 and 100,000.0.
$ HELP/MESSAGE HPARITH
HPARITH, high performance arithmetic trap, Imask='xxxxxxxx',
Fmask='xxxxxxxx', summary='xx', PC='xxxxxxxx',
PS='xxxxxxxx'
Facility: SYSTEM, System Services
Explanation: The image performed an arithmetic or conversion operation that
resulted in an arithmetic trap.
When an arithmetic exception condition is detected, several
instructions can be in various stages of execution. These
instructions are allowed to finish before the arithmetic trap
can be initiated. Some of these instructions can themselves
cause further arithmetic traps. Thus it is possible for
several arithmetic traps to be reported simultaneously.
The Imask parameter records all integer registers that were
targets of the instructions that set the bits in the exception
summary. Bit 0 corresponds to R0, bit 1 corresponds to R1, and
so on.
The Fmask parameter records all floating-point registers that
were targets of the instructions that set the bits in the
exception summary. Bit 0 corresponds to F0, bit 1 corresponds
to F1, and so on.
The exception summary parameter records the various types of
arithmetic traps that can occur together:
______________________________________________________________
Bit
Set_____Meaning_______________________________________________
Bit 0 Software Completion
All the other arithmetic exception bits were set by
floating-operate instructions with the /S software
completion trap modifier set.
Bit 1 Invalid Operation
An attempt was made to perform a floating
arithmetic, conversion, or comparison operation,
and one or more of the operand values was illegal.
Bit 2 Division by Zero
An attempt was made to perform a floating divide
operation with a divisor of 0.
Bit 3 Overflow
A floating arithmetic or conversion operation
overflowed the destination exponent.
Bit 4 Underflow
A floating arithmetic or conversion operation
underflowed the destination exponent.
Bit 5 Inexact Result
A floating arithmetic or conversion operation gave
a result that differed from the mathematically
exact result.
Bit 6 Integer Overflow
An integer arithmetic operation or a conversion
operation from floating to integer overflowed the
__________destination_precision.______________________________
The PC parameter is the virtual address of the next
instruction. This is defined as the virtual address of the
first instruction not executed after the trap condition was
recognized.
User Action: Check the program listing to verify that the operands or
variables are specified correctly.
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