[PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[HAO CHEN GUI]

Hi,
  The patch escalates the failure when Hollerith constant to real conversion
fails in native_interpret_expr. It finally reports an "Unclassifiable
statement" error.

  The patch of pr95450 added a verification for decoding/encoding checking
in native_interpret_expr. native_interpret_expr may fail on real type
conversion and returns a NULL tree then. But upper layer calls don't handle
the failure so that an ICE is reported when the verification fails.

  IBM long double is an example. It doesn't have a unique memory presentation
for some real values. So it may not pass the verification. The new test
case shows the problem.

  Bootstrapped and tested on powerpc64-linux BE and LE with no regressions.

Thanks
Gui Haochen

ChangeLog
2023-03-01  Haochen Gui <guihaoc@linux.ibm.com>

gcc/
	PR target/103628
	* fortran/target-memory.cc (gfc_interpret_float): Return FAIL when
	native_interpret_expr gets a NULL tree.
	* fortran/arith.cc (gfc_hollerith2real): Return NULL when
	gfc_interpret_float fails.

gcc/testsuite/
	PR target/103628
	* gfortran.dg/pr103628.f90: New.


patch.diff
diff --git a/gcc/fortran/arith.cc b/gcc/fortran/arith.cc
index c0d12cfad9d..d3d38c7eb6a 100644
--- a/gcc/fortran/arith.cc
+++ b/gcc/fortran/arith.cc
@@ -2752,10 +2752,12 @@ gfc_hollerith2real (gfc_expr *src, int kind)
   result = gfc_get_constant_expr (BT_REAL, kind, &src->where);

   hollerith2representation (result, src);
-  gfc_interpret_float (kind, (unsigned char *) result->representation.string,
-		       result->representation.length, result->value.real);
-
-  return result;
+  if (gfc_interpret_float (kind,
+			   (unsigned char *) result->representation.string,
+			   result->representation.length, result->value.real))
+    return result;
+  else
+    return NULL;
 }

 /* Convert character to real.  The constant will be padded or truncated.  */
diff --git a/gcc/fortran/target-memory.cc b/gcc/fortran/target-memory.cc
index 7ce7d736629..04afc357e3c 100644
--- a/gcc/fortran/target-memory.cc
+++ b/gcc/fortran/target-memory.cc
@@ -417,10 +417,13 @@ gfc_interpret_float (int kind, unsigned char *buffer, size_t buffer_size,
 {
   gfc_set_model_kind (kind);
   mpfr_init (real);
-  gfc_conv_tree_to_mpfr (real,
-			 native_interpret_expr (gfc_get_real_type (kind),
-						buffer, buffer_size));

+  tree source  = native_interpret_expr (gfc_get_real_type (kind), buffer,
+					buffer_size);
+  if (!source)
+    return 0;
+
+  gfc_conv_tree_to_mpfr (real, source);
   return size_float (kind);
 }

diff --git a/gcc/testsuite/gfortran.dg/pr103628.f90 b/gcc/testsuite/gfortran.dg/pr103628.f90
new file mode 100644
index 00000000000..e49aefc18fd
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr103628.f90
@@ -0,0 +1,14 @@
+! { dg-do compile { target powerpc*-*-* } }
+! { dg-options "-O2 -mabi=ibmlongdouble" }
+
+! Test to ensure that it reports an "Unclassifiable statement" error
+! instead of throwing an ICE when the memory represent of the HOLLERITH
+! string is not unique with ibm long double encoding.
+
+program main
+  integer, parameter :: k = 16
+  real(kind = k):: b = 4h1234
+end program main
+
+! { dg-warning "Conversion from HOLLERITH" "warning" { target powerpc*-*-* } 10 }
+! { dg-error "Unclassifiable statement" "error" { target powerpc*-*-* } 10 }

Re: [PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[Tobias Burnus]

Hi,

Please CC fortran@gcc for Fortran patches.

Fortraners: Please see my add-on suggestion/.diff for 'do_simply' below and
the original email at
https://gcc.gnu.org/pipermail/gcc-patches/2023-March/613019.html

On 01.03.23 08:09, HAO CHEN GUI via Gcc-patches wrote:
> The patch escalates the failure when Hollerith constant to real conversion
> fails in native_interpret_expr. It finally reports an "Unclassifiable
> statement" error.
I think we should do better than this (cf. below).
>    The patch of pr95450 added a verification for decoding/encoding checking
> in native_interpret_expr. native_interpret_expr may fail on real type
> conversion and returns a NULL tree then. But upper layer calls don't handle
> the failure so that an ICE is reported when the verification fails.
>
>    IBM long double is an example. It doesn't have a unique memory presentation
> for some real values. So it may not pass the verification. The new test
> case shows the problem.
>
> Bootstrapped and tested on powerpc64-linux BE and LE with no regressions.
I think the patch OK except for two items:
> ChangeLog
> 2023-03-01  Haochen Gui <guihaoc@linux.ibm.com>
>
> gcc/
>       PR target/103628
>       * fortran/target-memory.cc (gfc_interpret_float): Return FAIL when
>       native_interpret_expr gets a NULL tree.
>       * fortran/arith.cc (gfc_hollerith2real): Return NULL when
>       gfc_interpret_float fails.
>
> gcc/testsuite/
>       PR target/103628
>       * gfortran.dg/pr103628.f90: New.
...
> --- a/gcc/fortran/target-memory.cc
> +++ b/gcc/fortran/target-memory.cc
> @@ -417,10 +417,13 @@ gfc_interpret_float (int kind, unsigned char *buffer, size_t buffer_size,
>   {
>     gfc_set_model_kind (kind);
>     mpfr_init (real);
> -  gfc_conv_tree_to_mpfr (real,
> -                      native_interpret_expr (gfc_get_real_type (kind),
> -                                             buffer, buffer_size));
>
> +  tree source  = native_interpret_expr (gfc_get_real_type (kind), buffer,
> +                                     buffer_size);
> +  if (!source)
> +    return 0;
> +
> +  gfc_conv_tree_to_mpfr (real, source);
Can you move the mpfr_init before the 'gfc_conv...mfpr' to avoid
pointless allocation/leaks by mpfr_init.
> --- /dev/null
> +++ b/gcc/testsuite/gfortran.dg/pr103628.f90
> @@ -0,0 +1,14 @@
> +! { dg-do compile { target powerpc*-*-* } }
> +! { dg-options "-O2 -mabi=ibmlongdouble" }
> +
> +! Test to ensure that it reports an "Unclassifiable statement" error
> +! instead of throwing an ICE when the memory represent of the HOLLERITH
> +! string is not unique with ibm long double encoding.
> ...
> +  real(kind = k):: b = 4h1234
> ...
> +! { dg-warning "Conversion from HOLLERITH" "warning" { target powerpc*-*-* } 10 }
> +! { dg-error "Unclassifiable statement" "error" { target powerpc*-*-* } 10 }

I find a generic error pointing to the beginning of the line not that helpful.
I did wonder about something specific, but at the end for a rather special case,
a generic catch-all for 'do_simplify' seems to make sense. The callers of 'do_simplify'
clearly assume that this function will always (indirectly) generate an error message
if an error occurs. With my change, the result is:

    10 |   real(kind = k):: b = 4h1234
       |                      1
Error: Cannot simplify expression at (1)

That's with:

diff --git a/gcc/fortran/intrinsic.cc b/gcc/fortran/intrinsic.cc
index 64821c84543..b60d92a0665 100644
--- a/gcc/fortran/intrinsic.cc
+++ b/gcc/fortran/intrinsic.cc
@@ -27,2 +27,3 @@ along with GCC; see the file COPYING3.  If not see
  #include "intrinsic.h"
+#include "diagnostic.h" /* For errorcount.  */

@@ -4622,2 +4623,3 @@ do_simplify (gfc_intrinsic_sym *specific, gfc_expr *e)
    gfc_actual_arglist *arg;
+  int old_errorcount = errorcount;

@@ -4710,3 +4712,7 @@ finish:
    if (result == &gfc_bad_expr)
-    return false;
+    {
+      if (errorcount == old_errorcount)
+       gfc_error ("Cannot simplify expression at %L", &e->where);
+      return false;
+    }


Tobias

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Re: [PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[Steve Kargl]

On Wed, Mar 01, 2023 at 10:40:15AM +0100, Tobias Burnus wrote:
> > --- /dev/null
> > +++ b/gcc/testsuite/gfortran.dg/pr103628.f90
> > @@ -0,0 +1,14 @@
> > +! { dg-do compile { target powerpc*-*-* } }
> > +! { dg-options "-O2 -mabi=ibmlongdouble" }
> > +
> > +! Test to ensure that it reports an "Unclassifiable statement" error
> > +! instead of throwing an ICE when the memory represent of the HOLLERITH
> > +! string is not unique with ibm long double encoding.
> > ...
> > +  real(kind = k):: b = 4h1234

This should be rejected with an error message.  Hollerith was 
deleted from Fortran in Appendix C-1 of the Fortran 77 standard.
The appearance of a Hollerith entity in an initialization
expression has never be conforming.

In fact, Hollerith should be hidden behind a -fallow-hollerith
option and added to -std=legacy.

> diff --git a/gcc/fortran/intrinsic.cc b/gcc/fortran/intrinsic.cc
> index 64821c84543..b60d92a0665 100644
> --- a/gcc/fortran/intrinsic.cc
> +++ b/gcc/fortran/intrinsic.cc
> @@ -27,2 +27,3 @@ along with GCC; see the file COPYING3.  If not see
>  #include "intrinsic.h"
> +#include "diagnostic.h" /* For errorcount.  */
> 
> @@ -4622,2 +4623,3 @@ do_simplify (gfc_intrinsic_sym *specific, gfc_expr *e)
>    gfc_actual_arglist *arg;
> +  int old_errorcount = errorcount;
> 
> @@ -4710,3 +4712,7 @@ finish:
>    if (result == &gfc_bad_expr)
> -    return false;
> +    {
> +      if (errorcount == old_errorcount)
> +       gfc_error ("Cannot simplify expression at %L", &e->where);
> +      return false;
> +    }

I'm okay with this suggestion.  

-- 
Steve

Re: [PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[Bernhard Reutner-Fischer]

On Wed, 1 Mar 2023 10:40:15 +0100
Tobias Burnus <tobias@codesourcery.com> wrote:

> Hi,
> 
> Please CC fortran@gcc for Fortran patches.

> > --- a/gcc/fortran/target-memory.cc
> > +++ b/gcc/fortran/target-memory.cc
> > @@ -417,10 +417,13 @@ gfc_interpret_float (int kind, unsigned char *buffer, size_t buffer_size,
> >   {
> >     gfc_set_model_kind (kind);
> >     mpfr_init (real);
> > -  gfc_conv_tree_to_mpfr (real,
> > -                      native_interpret_expr (gfc_get_real_type (kind),
> > -                                             buffer, buffer_size));
> >
> > +  tree source  = native_interpret_expr (gfc_get_real_type (kind), buffer,

s/source  = native/source = native/

additionally to moving mpfr_init around and the other comments.
Please send an updated, regtested patch?
thanks && cheers,

Re: [PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[Bernhard Reutner-Fischer]

On Wed, 1 Mar 2023 07:39:40 -0800
Steve Kargl via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:

> In fact, Hollerith should be hidden behind a -fallow-hollerith
> option and added to -std=legacy.

While i'd be all for that, in my mind this will block off literally all
consultants and quite some scientists unless we error out
with a specific hint to an option that re-enable this.

So yea, but please forgivingly for the decades to come?

HTH,

Re: [PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[Steve Kargl]

On Thu, Mar 02, 2023 at 01:07:32AM +0100, Bernhard Reutner-Fischer wrote:
> On Wed, 1 Mar 2023 07:39:40 -0800
> Steve Kargl via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> 
> > In fact, Hollerith should be hidden behind a -fallow-hollerith
> > option and added to -std=legacy.
> 
> While i'd be all for that, in my mind this will block off literally all
> consultants and quite some scientists unless we error out
> with a specific hint to an option that re-enable this.
> 
> So yea, but please forgivingly for the decades to come?
> 

It has already been decades.  It seems to me that only
way to motivate people to fix their code is to nag.

Hollerith is pre-F77 era code.  gfortran already provide a
warning.  The warning should be made into an error, and yes,
it can point to -fallow-hollerith.  The option would downgrade
the error to a warning.  The only way to suppress the warning
is to suppress all warnings with -w.   See -fallow-invalid-boz.

% cat > a.f90
program foo            ! free-form source code is post-f77.
   real :: b = 4H1234  ! No code, in particular, legacy has 
   print *, b          ! initialization expressions.
end program foo
% gfcx -o z a.f90
a.f90:2:14:

    2 |    real :: b = 4H1234
      |              1
Warning: Extension: Conversion from HOLLERITH to REAL(4) at (1)
a.f90:2:18:

    2 |    real :: b = 4H1234
      |                  1
Warning: Legacy Extension: Hollerith constant at (1)

-- 
Steve

Re: [PATCH, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[Kewen.Lin]

Hi Haochen,

on 2023/3/1 15:09, HAO CHEN GUI wrote:
> Hi,
>   The patch escalates the failure when Hollerith constant to real conversion
> fails in native_interpret_expr. It finally reports an "Unclassifiable
> statement" error.
> 
>   The patch of pr95450 added a verification for decoding/encoding checking
> in native_interpret_expr. native_interpret_expr may fail on real type
> conversion and returns a NULL tree then. But upper layer calls don't handle
> the failure so that an ICE is reported when the verification fails.
> 
>   IBM long double is an example. It doesn't have a unique memory presentation
> for some real values. So it may not pass the verification. The new test
> case shows the problem.
> 
>   Bootstrapped and tested on powerpc64-linux BE and LE with no regressions.
> 
> Thanks
> Gui Haochen
> 
> ChangeLog
> 2023-03-01  Haochen Gui <guihaoc@linux.ibm.com>
> 
> gcc/
> 	PR target/103628
> 	* fortran/target-memory.cc (gfc_interpret_float): Return FAIL when
> 	native_interpret_expr gets a NULL tree.
> 	* fortran/arith.cc (gfc_hollerith2real): Return NULL when
> 	gfc_interpret_float fails.
> 
> gcc/testsuite/
> 	PR target/103628
> 	* gfortran.dg/pr103628.f90: New.
> 
> 
> patch.diff
> diff --git a/gcc/fortran/arith.cc b/gcc/fortran/arith.cc
> index c0d12cfad9d..d3d38c7eb6a 100644
> --- a/gcc/fortran/arith.cc
> +++ b/gcc/fortran/arith.cc
> @@ -2752,10 +2752,12 @@ gfc_hollerith2real (gfc_expr *src, int kind)
>    result = gfc_get_constant_expr (BT_REAL, kind, &src->where);
> 
>    hollerith2representation (result, src);
> -  gfc_interpret_float (kind, (unsigned char *) result->representation.string,
> -		       result->representation.length, result->value.real);
> -
> -  return result;
> +  if (gfc_interpret_float (kind,
> +			   (unsigned char *) result->representation.string,
> +			   result->representation.length, result->value.real))
> +    return result;
> +  else
> +    return NULL;
>  }
> 
>  /* Convert character to real.  The constant will be padded or truncated.  */
> diff --git a/gcc/fortran/target-memory.cc b/gcc/fortran/target-memory.cc
> index 7ce7d736629..04afc357e3c 100644
> --- a/gcc/fortran/target-memory.cc
> +++ b/gcc/fortran/target-memory.cc
> @@ -417,10 +417,13 @@ gfc_interpret_float (int kind, unsigned char *buffer, size_t buffer_size,
>  {
>    gfc_set_model_kind (kind);
>    mpfr_init (real);
> -  gfc_conv_tree_to_mpfr (real,
> -			 native_interpret_expr (gfc_get_real_type (kind),
> -						buffer, buffer_size));
> 
> +  tree source  = native_interpret_expr (gfc_get_real_type (kind), buffer,
> +					buffer_size);
> +  if (!source)
> +    return 0;
> +
> +  gfc_conv_tree_to_mpfr (real, source);
>    return size_float (kind);
>  }
> 
> diff --git a/gcc/testsuite/gfortran.dg/pr103628.f90 b/gcc/testsuite/gfortran.dg/pr103628.f90
> new file mode 100644
> index 00000000000..e49aefc18fd
> --- /dev/null
> +++ b/gcc/testsuite/gfortran.dg/pr103628.f90
> @@ -0,0 +1,14 @@
> +! { dg-do compile { target powerpc*-*-* } }
> +! { dg-options "-O2 -mabi=ibmlongdouble" }

Since this test case is powerpc only, I think it can be moved to gcc/testsuite/gcc.target/powerpc/ppc-fortran.

BR,
Kewen