Compute proper length for dynamic types of TYPE_CODE_TYPEDEF

This patch fixes gdb/21356 in which we hit an assertion in
value_contents_bits_eq:

(gdb) p container_object2
(gdb) p container_object2
$1 = {_container_member2 = 15, _vla_struct_object2 = {_some_member = 0,
    _vla_field = {
../../src/gdb/value.c:829: internal-error: \
  int value_contents_bits_eq(const value*, int, const value*, int, int): \
  Assertion `offset1 + length \
             <= TYPE_LENGTH (val1->enclosing_type) * TARGET_CHAR_BIT' failed.

This is happening because TYPE_LENGTH (val1->enclosing_type) is erroneously
based on enclosing_type, which is a typedef, instead of the actual underlying
type.

This can be traced back to resolve_dynamic_struct, where the size of the
type is computed:
...
        TYPE_FIELD_TYPE (resolved_type, i)
          = resolve_dynamic_type_internal (TYPE_FIELD_TYPE (resolved_type, i),
                                           &pinfo, 0);
        gdb_assert (TYPE_FIELD_LOC_KIND (resolved_type, i)
                    == FIELD_LOC_KIND_BITPOS);

        new_bit_length = TYPE_FIELD_BITPOS (resolved_type, i);
        if (TYPE_FIELD_BITSIZE (resolved_type, i) != 0)
          new_bit_length += TYPE_FIELD_BITSIZE (resolved_type, i);
        else
          new_bit_length += (TYPE_LENGTH (TYPE_FIELD_TYPE (resolved_type, i))
                             * TARGET_CHAR_BIT);
...

In this function, resolved_type is TYPE_CODE_TYPEDEF which is not what we
want to use to calculate the size of the actual field.

This patch fixes this and the similar problem in resolve_dynamic_union.

gdb/ChangeLog:
2020-06-11  Keith Seitz  <keiths@redhat.com>

	PR gdb/21356
	* gdbtypes.c (resolve_dynamic_union, resolve_dynamic_struct):
	Resolve typedefs for type length calculations.

gdb/testsuite/ChangeLog:
2020-06-11  Keith Seitz  <keiths@redhat.com>

	PR gdb/21356
	* gdb.base/vla-datatypes.c (vla_factory): Add typedef for struct
	vla_struct.
	Add new struct vla_typedef and union vla_typedef_union and
	corresponding instantiation objects.
	Initialize new objects.
	* gdb.base/vla-datatypes.exp: Add tests for vla_typedef_struct_object
	and vla_typedef_union_object.
	Fixup type for vla_struct_object.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2020-06-11  Keith Seitz  <keiths@redhat.com>
+
+	PR gdb/21356
+	* gdbtypes.c (resolve_dynamic_union, resolve_dynamic_struct):
+	Resolve typedefs for type length calculations.
+
 2020-06-10  Tom de Vries  <tdevries@suse.de>
 
 	PR ada/24713

gdb/gdbtypes.c

@@ -2264,8 +2264,10 @@ resolve_dynamic_union (struct type *type,
       t = resolve_dynamic_type_internal (resolved_type->field (i).type (),
 					 addr_stack, 0);
       resolved_type->field (i).set_type (t);
-      if (TYPE_LENGTH (t) > max_len)
+
-	max_len = TYPE_LENGTH (t);
+      struct type *real_type = check_typedef (t);
+      if (TYPE_LENGTH (real_type) > max_len)
+	max_len = TYPE_LENGTH (real_type);
     }
 
   TYPE_LENGTH (resolved_type) = max_len;
@@ -2521,8 +2523,12 @@ resolve_dynamic_struct (struct type *type,
       if (TYPE_FIELD_BITSIZE (resolved_type, i) != 0)
 	new_bit_length += TYPE_FIELD_BITSIZE (resolved_type, i);
       else
-	new_bit_length += (TYPE_LENGTH (resolved_type->field (i).type ())
+	{
-			   * TARGET_CHAR_BIT);
+	  struct type *real_type
+	    = check_typedef (resolved_type->field (i).type ());
+
+	  new_bit_length += (TYPE_LENGTH (real_type) * TARGET_CHAR_BIT);
+	}
 
       /* Normally, we would use the position and size of the last field
 	 to determine the size of the enclosing structure.  But GCC seems

gdb/testsuite/ChangeLog

@@ -1,3 +1,15 @@
+2020-06-11  Keith Seitz  <keiths@redhat.com>
+
+	PR gdb/21356
+	* gdb.base/vla-datatypes.c (vla_factory): Add typedef for struct
+	vla_struct.
+	Add new struct vla_typedef and union vla_typedef_union and
+	corresponding instantiation objects.
+	Initialize new objects.
+	* gdb.base/vla-datatypes.exp: Add tests for vla_typedef_struct_object
+	and vla_typedef_union_object.
+	Fixup type for vla_struct_object.
+
 2020-06-11  Tom de Vries  <tdevries@suse.de>
 
 	* lib/gdb.exp (with_override): New proc, factored out of ...

gdb/testsuite/gdb.base/vla-datatypes.c

@@ -50,7 +50,10 @@ vla_factory (int n)
   {
     int something;
     int vla_field[n];
-  } vla_struct_object;
+  };
+  /* Define a typedef for a VLA structure.  */
+  typedef struct vla_struct vla_struct_typedef;
+  vla_struct_typedef vla_struct_object;
 
   struct inner_vla_struct
   {
@@ -59,14 +62,33 @@ vla_factory (int n)
     int after;
   } inner_vla_struct_object;
 
+  /* Define a structure which uses a typedef for the VLA field
+     to make sure that GDB creates the proper type for this field,
+     preventing a possible assertion failure (see gdb/21356).  */
+  struct vla_struct_typedef_struct_member
+  {
+    int something;
+    vla_struct_typedef vla_object;
+  } vla_struct_typedef_struct_member_object;
+
   union vla_union
   {
     int vla_field[n];
   } vla_union_object;
 
+  /* Like vla_struct_typedef_struct_member but a union type.  */
+  union vla_struct_typedef_union_member
+  {
+    int something;
+    vla_struct_typedef vla_object;
+  } vla_struct_typedef_union_member_object;
+
   vla_struct_object.something = n;
   inner_vla_struct_object.something = n;
   inner_vla_struct_object.after = n;
+  vla_struct_typedef_struct_member_object.something = n * 2;
+  vla_struct_typedef_struct_member_object.vla_object.something = n * 3;
+  vla_struct_typedef_union_member_object.vla_object.something = n + 1;
   for (i = 0; i < n; i++)
     {
       int_vla[i] = i*2;
@@ -85,6 +107,10 @@ vla_factory (int n)
       vla_struct_object.vla_field[i] = i*2;
       vla_union_object.vla_field[i] = i*2;
       inner_vla_struct_object.vla_field[i] = i*2;
+      vla_struct_typedef_struct_member_object.vla_object.vla_field[i]
+	= i * 3;
+      vla_struct_typedef_union_member_object.vla_object.vla_field[i]
+	= i * 3 - 1;
     }
 
   size_t int_size        = sizeof(int_vla);     /* vlas_filled */

gdb/testsuite/gdb.base/vla-datatypes.exp

@@ -45,6 +45,10 @@ gdb_test "print vla_struct_object" \
     "\\\{something = 5, vla_field = \\\{0, 2, 4, 6, 8\\\}\\\}"
 gdb_test "print vla_union_object" \
     "\\\{vla_field = \\\{0, 2, 4, 6, 8\\\}\\\}"
+gdb_test "print vla_struct_typedef_struct_member_object" \
+    "\\\{something = 10, vla_object = \\\{something = 15, vla_field = \\\{0, 3, 6, 9, 12\\\}\\\}\\\}"
+gdb_test "print vla_struct_typedef_union_member_object" \
+    "\\\{something = 6, vla_object = \\\{something = 6, vla_field = \\\{-1, 2, 5, 8, 11\\\}\\\}\\\}"
 
 # Check whatis of VLA's.
 gdb_test "whatis int_vla" "type = int \\\[5\\\]"
@@ -61,7 +65,7 @@ gdb_test "whatis unsigned_short_vla" \
 gdb_test "whatis unsigned_char_vla" "type = unsigned char \\\[5\\\]"
 gdb_test "whatis foo_vla" "type = struct foo \\\[5\\\]"
 gdb_test "whatis bar_vla" "type = BAR \\\[5\\\]"
-gdb_test "whatis vla_struct_object" "type = struct vla_struct"
+gdb_test "whatis vla_struct_object" "type = vla_struct_typedef"
 gdb_test "whatis vla_union_object" "type = union vla_union"
 
 # Check ptype of VLA's.