[PATCHv2, gfortran] Escalate failure when Hollerith constant to real conversion fails [PR103628]

[HAO CHEN GUI via Gcc-patches]

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.

  Compared to last version, this version moves the mpfr_init after NULL tree
test and fixes the format problem according to Tobias's advice. Thanks a lot.

Gui Haochen
Thanks

ChangeLog
2023-03-01  Haochen Gui <guih...@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..0c47aa6b842 100644
--- a/gcc/fortran/target-memory.cc
+++ b/gcc/fortran/target-memory.cc
@@ -416,11 +416,14 @@ gfc_interpret_float (int kind, unsigned char *buffer, 
size_t buffer_size,
                     mpfr_t real)
 {
   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;
+
+  mpfr_init (real);
+  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 }