2014-01-01 03:54:24 +00:00
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-- Copyright 2012-2014 Free Software Foundation, Inc.
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[Ada] Handle reference to array descriptors
This patch is to help handle aliased array variables, such as:
type Bounded is array (Integer range <>) of Integer;
function New_Bounded (Low, High : Integer) return Bounded;
BT : aliased Bounded := New_Bounded (Low => 1, High => 3);
In that case, the compiler describes variable "BT" as a reference
to a thin pointer, and GDB is unable to print its value:
(gdb) p bt
$1 =
The problems starts when ada_value_print deconstructs the struct
value into contents and address in order to call val_print. It
turns out in this case that "bt" is not an lval. In the debug
information, this variable's location is described as:
.uleb128 0xd # (DIE (0xe0) DW_TAG_variable)
.ascii "bt\0" # DW_AT_name
[...]
.byte 0x6 # DW_AT_location
.byte 0x91 # DW_OP_fbreg
.sleb128 -56
.byte 0x6 # DW_OP_deref
.byte 0x23 # DW_OP_plus_uconst
.uleb128 0x8
.byte 0x9f # DW_OP_stack_value
So, when ada_value_print passes the bt's (value) address, it passes
in effect a meaningless address. The problem continues shortly after
when ada_val_print_1 re-creates the value from the contents and address.
The value has become an lval_memory, with a null address.
As a result, we trigger a memory error later on, while trying to
read the array bounds in order to transform our value into a simple
array.
To avoid the problem entirely, the fix is to coerce references before
transforming array descriptors into simple arrays.
gdb/ChangeLog:
* ada-valprint.c (ada_val_print_1): If our value is a reference
to an array descriptor, dereference it before converting it
to a simple array.
gdb/testsuite/ChangeLog:
* gdb.ada/aliased_array: New testcase.
2012-02-29 19:33:02 +00:00
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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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with Pck; use Pck;
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procedure Foo is
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BT : aliased Bounded := New_Bounded (Low => 1, High => 3);
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begin
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Do_Nothing (BT'Address); -- STOP
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end Foo;
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