Re: [Patch, Fortran] Print floating-point exception status after STOP/ERROR STOP

[Mikael Morin <mikael dot morin at sfr dot fr>]

Hello,

Le 16/06/2013 19:33, Tobias Burnus a écrit :
> * PING *
> 
> Minor change: Jakub suggested to print no exception status with older
> gfortran programs. Hence, the library now defaults to 0. (Older programs
> do not pass this argument to the library.) - I also updated
> gfortran.texi for that change.
> 
> Tobias
> 
> 
> On June 12, 2013 17:50, Tobias Burnus wrote:
>> Updated version:
>> * Uros suggestions are incorporated
>> * Changed from -f(no-)underflow-warning to
>> -ffpe-summary=[none,all,underflow,...]
>>
>> Tobias Burnus wrote:
>>> The attached patch causes gfortran-compiled programs to print
>>> warnings like
>> Note: The following floating-point exception are signalling:
>> IEEE_DIVIDE_BY_ZERO
>>> when STOP / ERROR STOP is invoked. That's required by Fortran 2008
>>> (8.4 STOP and ERROR STOP statements):
>>>
>>> "If any exception (14) is signaling on that image, the processor
>>> shall issue a warning indicating which exceptions are signaling; this
>>> warning shall be on the unit identified by the named constant ERROR
>>> UNIT (13.8.2.8)."
>>
>>> One surely could extend it to allow to completely disable the warning
>>> - or to make it more fine grained like "none", "all" plus all single
>>> flags (including underflow, denormal and inexact, where by default
>>> one leaves out inexact).
>>
>> Thinking about it, I think that's the better solution: It makes
>> (optionally) inexact available and also allows to fully disable the
>> feature. I am sure that there are users who would like to have that
>> choice. Hence, I update the argument handling and libgfortran's stop.c.
>>
>> Additions from the J3 list:
>> * IBM's "XLF compiler has an option to report fp exceptions including
>> underflow and inexact.  It is default OFF."
>> (which matches ifort)
>>
>>> Build and regtested on x86-64-gnu-linux.
>>> OK for the trunk?
>>
>> Tobias
>>
>> PS: I filled PR 57598 to track the warning handling for coarrays.
> 

Two nits below:

> @@ -515,17 +525,37 @@ gfc_handle_fpe_trap_option (const char *arg)
>  	pos++;
>  
>        result = 0;
> -      for (n = 0; exception[n] != NULL; n++)
> +      if (!trap && strncmp ("none", arg, pos) == 0)
> +	{
> +	  gfc_option.fpe_summary = 0;
> +	  arg += pos;
> +	  pos = 0;
> +	  continue;
> +	}
> +      else if (!trap && strncmp ("all", arg, pos) == 0)
>  	{
> +	  gfc_option.fpe_summary = GFC_FPE_INVALID | GFC_FPE_DENORMAL
> +				   | GFC_FPE_ZERO | GFC_FPE_OVERFLOW
> +				   | GFC_FPE_UNDERFLOW | GFC_FPE_INEXACT;
> +	  arg += pos;
> +	  pos = 0;
> +	  continue;
> +	}
> +      else
> +	for (n = 0; exception[n] != NULL; n++)
> +	  {
>  	  if (exception[n] && strncmp (exception[n], arg, pos) == 0)
>  	    {
> -	      gfc_option.fpe |= opt_exception[n];
> +	      if (trap)
> +		gfc_option.fpe |= opt_exception[n];
> +	      else
> +		gfc_option.fpe_summary |= opt_exception[n];
>  	      arg += pos;
>  	      pos = 0;
>  	      result = 1;
>  	      break;
>  	    }
> -	}
> +	  }
>        if (!result)
>  	gfc_fatal_error ("Argument to -ffpe-trap is not valid: %s", arg);
-ffpe-trap and -ffpe-summary should better be distinguished here.

>      }

> diff --git a/libgfortran/runtime/stop.c b/libgfortran/runtime/stop.c
> index 4805412..2d4fb62 100644
> --- a/libgfortran/runtime/stop.c
> +++ b/libgfortran/runtime/stop.c
> @@ -32,6 +32,55 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
>  #endif
>  
>  
> +/* Fortran 2008 demands: If any exception (14) is signaling on that image, the
> +   processor shall issue a warning indicating which exceptions are signaling;
> +   this warning shall be on the unit identified by the named constant
> +   ERROR_UNIT (13.8.2.8).  In line with other compilers, we do not report
> +   inexact - and we optionally ignore underflow, cf. thread starting at
> +   http://mailman.j3-fortran.org/pipermail/j3/2013-June/006452.html.  */
> +
> +static void
> +report_exception (void)
> +{
> +  int set_excepts;
> +
> +  if (!compile_options.fpe_summary)
> +    return;
> +
> +  set_excepts = get_fpu_except_flags ();
> +  if ((set_excepts & compile_options.fpe_summary) == 0)
> +    return;
> +
> +  estr_write ("Note: The following floating-point exceptions are signalling:");
> +
> +  if ((compile_options.fpe_summary & GFC_FPE_INVALID)
> +      && (set_excepts & GFC_FPE_INVALID))
> +    estr_write (" IEEE INVALID FLAG");
Two underscores missing.

OK once fixed.

Thanks

Mikael