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

[Tobias Burnus <tobias@codesourcery.com>]

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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