old-cross-binutils/gdb/testsuite/gdb.ada/mi_dyn_arr/foo.adb

--  Copyright 2014 Free Software Foundation, Inc.
--
--  This program is free software; you can redistribute it and/or modify
--  it under the terms of the GNU General Public License as published by
--  the Free Software Foundation; either version 3 of the License, or
--  (at your option) any later version.
--
--  This program is distributed in the hope that it will be useful,
--  but WITHOUT ANY WARRANTY; without even the implied warranty of
--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
--  GNU General Public License for more details.
--
--  You should have received a copy of the GNU General Public License
--  along with this program.  If not, see <http://www.gnu.org/licenses/>.

with Pck; use Pck;
procedure Foo is
   --  The goal here is to have an array whose bounds are not
   --  known at compile time.
   BT : Bounded := New_Bounded (Low => 1, High => 3);
begin
   Do_Nothing (BT'Address);  -- STOP
end Foo;
[varobj] false type-changed status for reference to Ada array Given the following variable... BT : Bounded := New_Bounded (Low => 1, High => 3); ... where type Bounded is defined as a simple unconstrained array: type Bounded is array (Integer range <>) of Integer; Creating a varobj for that variable, and immediately asking for varobj updates, GDB says that our varobj changed types! (gdb) -var-create bt * bt ^done,name="bt",numchild="3",value="[3]",type="<ref> array (1 .. 3) of integer",has_more="0" (gdb) -var-update 1 * ^done,changelist=[{name="bt",value="[3]",in_scope="true",type_changed="true",new_type="<ref> array (1 .. 3) of integer",new_num_children="3",has_more="0"}] The expected output for the -var-update command is, in this case: (gdb) -var-update 1 * ^done,changelist=[] The problem occurs because the ada-varobj module does not handle references, and while the references gets stripped when the varobj gets created, it doesn't when computing varobj updates. More specifically, when creating the varobj, varobj_create creates a new value which is a reference to a TYPE_CODE_ARRAY. It then calls install_new_value which calls coerce_ref with the following comment: /* We are not interested in the address of references, and given that in C++ a reference is not rebindable, it cannot meaningfully change. So, get hold of the real value. / if (value) value = coerce_ref (value); This leaves the varobj's type component still a ref, while the varobj's value is now our array, without the ref. This explains why the "value" field in the varobj indicates an array with 3 elements "[3]" while the "type" field shows a ref to an array. Generally speaking, most users have said that showing the ref was a useful piece of information, so this patch is not touching this part. Next, when the user issues the -var-update request, varobj_update calls value_of_root to compute the varobj's new value as well as determine whether the value's type has changed or not. What happens in a nutshell is that it calls value_of_root_1 (which re-evaluates the expression and returns the corresponding new value), finds that the new value is not NULL, and thus asks whether it has mutated: else if (varobj_value_has_mutated (var, value, value_type (value))) This then indirectly delegates the determination to the language-specific callback, which fails, because it does not handle references. This patch fixes the issue by adjusting varobj_value_has_mutated to expect references, and strip them when seen. This allows the various language-specific implementations to remain unaware of references. gdb/ChangeLog: varobj.c (varobj_value_has_mutated): If NEW_VALUE is a reference, strip the reference layer before calling the lang_ops value_has_mutated callback. gdb/testsuite/ChangeLog: * gdb.ada/mi_dyn_arr: New testcase. 2014-03-20 14:43:08 +00:00			`-- Copyright 2014 Free Software Foundation, Inc.`
			`--`
			`-- This program is free software; you can redistribute it and/or modify`
			`-- it under the terms of the GNU General Public License as published by`
			`-- the Free Software Foundation; either version 3 of the License, or`
			`-- (at your option) any later version.`
			`--`
			`-- This program is distributed in the hope that it will be useful,`
			`-- but WITHOUT ANY WARRANTY; without even the implied warranty of`
			`-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the`
			`-- GNU General Public License for more details.`
			`--`
			`-- You should have received a copy of the GNU General Public License`
			`-- along with this program. If not, see <http://www.gnu.org/licenses/>.`

			`with Pck; use Pck;`
			`procedure Foo is`
			`-- The goal here is to have an array whose bounds are not`
			`-- known at compile time.`
			`BT : Bounded := New_Bounded (Low => 1, High => 3);`
			`begin`
			`Do_Nothing (BT'Address); -- STOP`
			`end Foo;`