gdb: change functions returning value contents to use gdb::array_view

The bug fixed by this [1] patch was caused by an out-of-bounds access to
a value's content.  The code gets the value's content (just a pointer)
and then indexes it with a non-sensical index.

This made me think of changing functions that return value contents to
return array_views instead of a plain pointer.  This has the advantage
that when GDB is built with _GLIBCXX_DEBUG, accesses to the array_view
are checked, making bugs more apparent / easier to find.

This patch changes the return types of these functions, and updates
callers to call .data() on the result, meaning it's not changing
anything in practice.  Additional work will be needed (which can be done
little by little) to make callers propagate the use of array_view and
reap the benefits.

[1] https://sourceware.org/pipermail/gdb-patches/2021-September/182306.html

Change-Id: I5151f888f169e1c36abe2cbc57620110673816f3

1 files changed, 36 insertions, 35 deletions

diff --git a/gdb/valarith.c b/gdb/valarith.c
index 07472ef..140ef44 100644
--- a/gdb/valarith.c
+++ b/gdb/valarith.c
@@ -716,7 +716,7 @@ value_concat (struct value *arg1, struct value *arg2)
 	      char_type = type2;
 
 	      inchar = (char) unpack_long (type2,
-					   value_contents (inval2));
+					   value_contents (inval2).data ());
 	      for (idx = 0; idx < count; idx++)
 		{
 		  ptr[idx] = inchar;
@@ -727,10 +727,8 @@ value_concat (struct value *arg1, struct value *arg2)
 	      char_type = TYPE_TARGET_TYPE (type2);
 
 	      for (idx = 0; idx < count; idx++)
-		{
-		  memcpy (&ptr[idx * inval2len], value_contents (inval2),
-			  inval2len);
-		}
+		memcpy (&ptr[idx * inval2len], value_contents (inval2).data (),
+			inval2len);
 	    }
 	  outval = value_string (ptr.data (), count * inval2len, char_type);
 	}
@@ -759,22 +757,22 @@ value_concat (struct value *arg1, struct value *arg2)
 	{
 	  char_type = type1;
 
-	  ptr[0] = (char) unpack_long (type1, value_contents (inval1));
+	  ptr[0] = (char) unpack_long (type1, value_contents (inval1).data ());
 	}
       else
 	{
 	  char_type = TYPE_TARGET_TYPE (type1);
 
-	  memcpy (ptr.data (), value_contents (inval1), inval1len);
+	  memcpy (ptr.data (), value_contents (inval1).data (), inval1len);
 	}
       if (type2->code () == TYPE_CODE_CHAR)
 	{
 	  ptr[inval1len] =
-	    (char) unpack_long (type2, value_contents (inval2));
+	    (char) unpack_long (type2, value_contents (inval2).data ());
 	}
       else
 	{
-	  memcpy (&ptr[inval1len], value_contents (inval2), inval2len);
+	  memcpy (&ptr[inval1len], value_contents (inval2).data (), inval2len);
 	}
       outval = value_string (ptr.data (), inval1len + inval2len, char_type);
     }
@@ -855,7 +853,7 @@ value_args_as_target_float (struct value *arg1, struct value *arg2,
   if (is_floating_type (type1))
     {
       *eff_type_x = type1;
-      memcpy (x, value_contents (arg1), TYPE_LENGTH (type1));
+      memcpy (x, value_contents (arg1).data (), TYPE_LENGTH (type1));
     }
   else if (is_integral_type (type1))
     {
@@ -874,7 +872,7 @@ value_args_as_target_float (struct value *arg1, struct value *arg2,
   if (is_floating_type (type2))
     {
       *eff_type_y = type2;
-      memcpy (y, value_contents (arg2), TYPE_LENGTH (type2));
+      memcpy (y, value_contents (arg2).data (), TYPE_LENGTH (type2));
     }
   else if (is_integral_type (type2))
     {
@@ -929,11 +927,11 @@ fixed_point_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
 	  type2 = type1;
 	}
 
-      v1.read_fixed_point (gdb::make_array_view (value_contents (arg1),
+      v1.read_fixed_point (gdb::make_array_view (value_contents (arg1).data (),
 						 TYPE_LENGTH (type1)),
 			   type_byte_order (type1), type1->is_unsigned (),
 			   type1->fixed_point_scaling_factor ());
-      v2.read_fixed_point (gdb::make_array_view (value_contents (arg2),
+      v2.read_fixed_point (gdb::make_array_view (value_contents (arg2).data (),
 						 TYPE_LENGTH (type2)),
 			   type_byte_order (type2), type2->is_unsigned (),
 			   type2->fixed_point_scaling_factor ());
@@ -944,7 +942,7 @@ fixed_point_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
       value *fp_val = allocate_value (type1);
 
       fp.write_fixed_point
-	(gdb::make_array_view (value_contents_raw (fp_val),
+	(gdb::make_array_view (value_contents_raw (fp_val).data (),
 			       TYPE_LENGTH (type1)),
 	 type_byte_order (type1),
 	 type1->is_unsigned (),
@@ -1204,7 +1202,7 @@ scalar_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
 				  v2.data (), &eff_type_v2);
       target_float_binop (op, v1.data (), eff_type_v1,
 			      v2.data (), eff_type_v2,
-			      value_contents_raw (val), result_type);
+			      value_contents_raw (val).data (), result_type);
     }
   else if (type1->code () == TYPE_CODE_BOOL
 	   || type2->code () == TYPE_CODE_BOOL)
@@ -1243,7 +1241,7 @@ scalar_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
       result_type = type1;
 
       val = allocate_value (result_type);
-      store_signed_integer (value_contents_raw (val),
+      store_signed_integer (value_contents_raw (val).data (),
 			    TYPE_LENGTH (result_type),
 			    type_byte_order (result_type),
 			    v);
@@ -1383,7 +1381,7 @@ scalar_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
 	    }
 
 	  val = allocate_value (result_type);
-	  store_unsigned_integer (value_contents_raw (val),
+	  store_unsigned_integer (value_contents_raw (val).data (),
 				  TYPE_LENGTH (value_type (val)),
 				  type_byte_order (result_type),
 				  v);
@@ -1512,7 +1510,7 @@ scalar_binop (struct value *arg1, struct value *arg2, enum exp_opcode op)
 	    }
 
 	  val = allocate_value (result_type);
-	  store_signed_integer (value_contents_raw (val),
+	  store_signed_integer (value_contents_raw (val).data (),
 				TYPE_LENGTH (value_type (val)),
 				type_byte_order (result_type),
 				v);
@@ -1559,8 +1557,8 @@ value_vector_widen (struct value *scalar_value, struct type *vector_type)
   val = allocate_value (vector_type);
   for (i = 0; i < high_bound - low_bound + 1; i++)
     /* Duplicate the contents of elval into the destination vector.  */
-    memcpy (value_contents_writeable (val) + (i * TYPE_LENGTH (eltype)),
-	    value_contents_all (elval), TYPE_LENGTH (eltype));
+    memcpy (value_contents_writeable (val).data () + (i * TYPE_LENGTH (eltype)),
+	    value_contents_all (elval).data (), TYPE_LENGTH (eltype));
 
   return val;
 }
@@ -1607,8 +1605,8 @@ vector_binop (struct value *val1, struct value *val2, enum exp_opcode op)
     {
       tmp = value_binop (value_subscript (val1, i),
 			 value_subscript (val2, i), op);
-      memcpy (value_contents_writeable (val) + i * elsize,
-	      value_contents_all (tmp),
+      memcpy (value_contents_writeable (val).data () + i * elsize,
+	      value_contents_all (tmp).data (),
 	      elsize);
      }
   value_free_to_mark (mark);
@@ -1666,10 +1664,10 @@ value_logical_not (struct value *arg1)
   type1 = check_typedef (value_type (arg1));
 
   if (is_floating_value (arg1))
-    return target_float_is_zero (value_contents (arg1), type1);
+    return target_float_is_zero (value_contents (arg1).data (), type1);
 
   len = TYPE_LENGTH (type1);
-  p = value_contents (arg1);
+  p = value_contents (arg1).data ();
 
   while (--len >= 0)
     {
@@ -1688,8 +1686,8 @@ value_strcmp (struct value *arg1, struct value *arg2)
 {
   int len1 = TYPE_LENGTH (value_type (arg1));
   int len2 = TYPE_LENGTH (value_type (arg2));
-  const gdb_byte *s1 = value_contents (arg1);
-  const gdb_byte *s2 = value_contents (arg2);
+  const gdb_byte *s1 = value_contents (arg1).data ();
+  const gdb_byte *s2 = value_contents (arg2).data ();
   int i, len = len1 < len2 ? len1 : len2;
 
   for (i = 0; i < len; i++)
@@ -1764,8 +1762,8 @@ value_equal (struct value *arg1, struct value *arg2)
 	   && ((len = (int) TYPE_LENGTH (type1))
 	       == (int) TYPE_LENGTH (type2)))
     {
-      p1 = value_contents (arg1);
-      p2 = value_contents (arg2);
+      p1 = value_contents (arg1).data ();
+      p2 = value_contents (arg2).data ();
       while (--len >= 0)
 	{
 	  if (*p1++ != *p2++)
@@ -1795,7 +1793,8 @@ value_equal_contents (struct value *arg1, struct value *arg2)
 
   return (type1->code () == type2->code ()
 	  && TYPE_LENGTH (type1) == TYPE_LENGTH (type2)
-	  && memcmp (value_contents (arg1), value_contents (arg2),
+	  && memcmp (value_contents (arg1).data (),
+		     value_contents (arg2).data (),
 		     TYPE_LENGTH (type1)) == 0);
 }
 
@@ -1870,7 +1869,7 @@ value_pos (struct value *arg1)
   if (is_integral_type (type) || is_floating_value (arg1)
       || (type->code () == TYPE_CODE_ARRAY && type->is_vector ())
       || type->code () == TYPE_CODE_COMPLEX)
-    return value_from_contents (type, value_contents (arg1));
+    return value_from_contents (type, value_contents (arg1).data ());
   else
     error (_("Argument to positive operation not a number."));
 }
@@ -1900,8 +1899,9 @@ value_neg (struct value *arg1)
       for (i = 0; i < high_bound - low_bound + 1; i++)
 	{
 	  tmp = value_neg (value_subscript (arg1, i));
-	  memcpy (value_contents_writeable (val) + i * TYPE_LENGTH (eltype),
-		  value_contents_all (tmp), TYPE_LENGTH (eltype));
+	  memcpy ((value_contents_writeable (val).data ()
+		   + i * TYPE_LENGTH (eltype)),
+		  value_contents_all (tmp).data (), TYPE_LENGTH (eltype));
 	}
       return val;
     }
@@ -1943,8 +1943,9 @@ value_complement (struct value *arg1)
       for (i = 0; i < high_bound - low_bound + 1; i++)
 	{
 	  tmp = value_complement (value_subscript (arg1, i));
-	  memcpy (value_contents_writeable (val) + i * TYPE_LENGTH (eltype),
-		  value_contents_all (tmp), TYPE_LENGTH (eltype));
+	  memcpy ((value_contents_writeable (val).data ()
+		   + i * TYPE_LENGTH (eltype)),
+		  value_contents_all (tmp).data (), TYPE_LENGTH (eltype));
 	}
     }
   else if (type->code () == TYPE_CODE_COMPLEX)
@@ -2005,7 +2006,7 @@ value_in (struct value *element, struct value *set)
       && eltype->code () != TYPE_CODE_ENUM
       && eltype->code () != TYPE_CODE_BOOL)
     error (_("First argument of 'IN' has wrong type"));
-  member = value_bit_index (settype, value_contents (set),
+  member = value_bit_index (settype, value_contents (set).data (),
 			    value_as_long (element));
   if (member < 0)
     error (_("First argument of 'IN' not in range"));