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Consider the following situation Ada code:
type Kind_T is (One, Two, Three);
type Time_Set_T is array (Kind_T) of Integer;
type T is record
Started : Time_Set_T;
end record;
Null_T : constant T := (Started => (others => 0));
My_Item : Pck.T := Pck.Null_T;
Trying to print the value of My_Item.Started is no problem:
(gdb) p item.started
$1 = (0, 0, 0)
However, if you save My_Item into a convenience variable first,
and then try to print a component of that record, you get
an unexpected memory error, instead of getting the same result.
For instance:
(gdb) set variable $item := item
(gdb) p $item.started
Cannot access memory at address 0x0
The issue occurs when, after we extracted the component from
the convenience variable, we next try to "fix" it (which is
ada-lang speak for resolving the type into a static type).
This is done in ada_to_fixed_value, which delegates to
ada_to_fixed_value_create via:
val = ada_to_fixed_value_create (value_type (val),
value_address (val), val);
And looking at ada_to_fixed_value_create, we see that:
struct type *type = ada_to_fixed_type (type0, 0, address, NULL, 1);
if (type == type0 && val0 != NULL)
return val0;
else
return value_from_contents_and_address (type, 0, address);
The part that interests us, in this case, is the "else" branch,
where we obviously make the implicit assumption that our object
has an address, which is not true, in this case, because we are
actually dealing with a convenience variable.
This patch plugs that hole by adding special handing for situations
where val does not live in memory. In that case, we just create
a not_lval value using val's contents.
gdb/ChangeLog:
* ada-lang.c (ada_to_fixed_value_create): Add handling of
the case where VALUE_LVAL (val0) is not lval_memory.
gdb/testsuite/ChangeLog:
* gdb.ada/convvar_comp: New testcase.
Tested on x86_64-linux.
35 lines
1.0 KiB
Plaintext
35 lines
1.0 KiB
Plaintext
# Copyright 2018 Free Software Foundation, Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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load_lib "ada.exp"
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standard_ada_testfile pb16_063
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if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug ]] != "" } {
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return -1
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}
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clean_restart ${testfile}
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if ![runto "break_me" ] then {
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perror "Couldn't run ${testfile}"
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return
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}
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gdb_test_no_output "set variable \$item := item"
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gdb_test "print \$item.started" \
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" = \\(0, 0, 0\\)"
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