On 17.07.21 02:49, Sandra Loosemore wrote:

This patch is for PR101317, one of the bugs uncovered by the TS29113
testsuite.  Here I'd observed that CFI_establish, etc was not
diagnosing some invalid-argument situations documented in the
standard, although it was properly catching others.  After fixing
those I discovered a couple small mistakes in the test cases and fixed
those too.

Some first comments – I think I have to read though the file
ISO_Fortran_binding.c itself and not only your patch.

--- a/libgfortran/runtime/ISO_Fortran_binding.c
+++ b/libgfortran/runtime/ISO_Fortran_binding.c
@@ -232,7 +232,16 @@ CFI_allocate (CFI_cdesc_t *dv, const CFI_index_t 
lower_bounds[],
    /* If the type is a Fortran character type, the descriptor's element
       length is replaced by the elem_len argument. */
    if (dv->type == CFI_type_char || dv->type == CFI_type_ucs4_char)
-    dv->elem_len = elem_len;
+    {
+      if (unlikely (compile_options.bounds_check) && elem_len == 0)
+     {
+       fprintf ("CFI_allocate: The supplied elem_len must be "
+                "greater than zero (elem_len = %d).\n",
+                (int) elem_len);

I think there is no need to use '(elem_len = %d)' given that it is always zero 
as stated in the error message itself.

(Appears twice)

However, the check itself is also wrong – cf. below.

 * * *

Talking about CFI_allocatable, there is also another bug in that function,
untouched by your patch:

 /* If the type is a character, the descriptor's element length is replaced
     by the elem_len argument. */
  if (dv->type == CFI_type_char || dv->type == CFI_type_ucs4_char ||
      dv->type == CFI_type_signed_char)
    dv->elem_len = elem_len;

The bug is that CFI_type_signed_char is not a character type.

+  else if (unlikely (compile_options.bounds_check)
+        && type < 0)
Pointless line break.
+           fprintf (stderr, "CFI_establish: Extents must be nonnegative "
+                    "(extents[%d] = %d).\n", i, (int)extents[i]);
+           return CFI_INVALID_EXTENT;
+         }

How about PRIiPTR + ptrdiff_t instead of %d + (int) cast? At least as
positive value, extent may exceed INT_MAX.

(Twice)

    if (result->type == CFI_type_char || result->type == CFI_type_ucs4_char)
-    result->elem_len = elem_len;
+    {
+      if (unlikely (compile_options.bounds_check) && elem_len == 0)
+     {
+       fprintf ("CFI_select_part: The supplied elem_len must be "
+                "greater than zero (elem_len = %d).\n",
+                (int) elem_len);

What's wrong with  ["", ""]? Or with:
  character(len=:), allocatable :: str2(:)
  str2 = [str1(5:4)]
both are len(...) == 0 arrays with 1 or 2 elements.

+       if (source->attribute == CFI_attribute_other
+           && source->rank > 0
+           && source->dim[source->rank - 1].extent == -1)
+         {
+           fprintf (stderr, "CFI_setpointer: The source is a "
+                    "nonallocatable nonpointer object that is an "
+                    "assumed-size array.\n");

I think you could just check for assumed rank – without
CFI_attribute_other in the 'if' and 'nonallocatable nonpointer' in the
error message. Only nonallocatable nonpointer variables can be of
assumed size (in Fortran); I think that makes the message simpler
(focusing on the issue) and if the C user passes an allocatable/pointer,
which is assumed rank, it is also a bug.

Tobias

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