  C programming, IEEE Floating Point? (HPARITH) 
 The Question is:
 
I have problems using RTL functions in a C++ program using IEEE floats. The
 following program will not run:
 
#include &lt;stdio.h&gt;
#include &lt;lib$routines.h&gt;
#pragma  nomember_alignment
 
main()
 
  float f1 = 1.0;
  lib$wait(&amp;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 &lt;cvt$routines.h&gt;
    #include &lt;cvtdef&gt;
    #include &lt;lib$routines.h&gt;
    #include &lt;libwaitdef.h&gt;
    #include &lt;ssdef.h&gt;
    #include &lt;stdio.h&gt;
    #include &lt;stsdef.h&gt;
 
    main()
      {
      float ieee_s = 1.0;
      int vax_f;
      int RetStat;
      int float_type = LIB$K_IEEE_S;
 
      RetStat = cvt$ftof(&amp;ieee_s,CVT$K_IEEE_S,&amp;vax_f,CVT$K_VAX_F,0);
      if (!$VMS_STATUS_SUCCESS( RetStat ))
        return RetStat;
      RetStat = lib$wait(&amp;vax_f);
      if (!$VMS_STATUS_SUCCESS( RetStat ))
        return RetStat;
      RetStat = lib$wait(&amp;ieee_s, 0, &amp;float_type);
      if (!$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.
 
 
 
 
 Answer written or last revised on  19-SEP-2001 
