(Ada) fix GDB crash printing packed array
Trying to print a packed array sometimes leads to a crash (see
attached testcase for an example of when this happens):
| (gdb) p bad
| [1] 65571 segmentation fault gdb -q foo
Variable "bad" is declared in the debug information as an array where
the array's type name has an XPnnn suffix:
| .uleb128 0xc # (DIE (0x566) DW_TAG_typedef)
| .long .LASF200 # DW_AT_name: "pck__t___XP1"
| [loc info attributes snipped]
| .long 0x550 # DW_AT_type
| .byte 0x1 # DW_AT_alignment
The signals to GDB that the debugging information follows a GNAT encoding
used for packed arrays, and an in order to decode it, we need to find
the type whose name is the same minus the "___XPnnn" suffix: "pck__t".
For that, we make a call to ada-lang.c::standard_lookup, which is
a simple function which essentially does:
| /* Return the result of a standard (literal, C-like) lookup of NAME in
| given DOMAIN, visible from lexical block BLOCK. */
|
| [...]
| sym = lookup_symbol_in_language (name, block, domain, language_c, 0);
Unfortunately for us, while the intent of this call was to perform
an exact-match lookup, in our case, it returns ... type pck__t___XP1
instead! In other words, it finds itself back. The reason why it finds
this type is a confluence of two factors:
(1) Forcing the lookup into language_c currently does not affect
how symbol matching is done anymore, because we look at the symbol's
language to determine which kind of matching should be done;
(2) The lookup searches the local context (via block) first, beforei
doing a more general lookup. And looking at the debug info for
the main subprogram, we see that type "pck__t" is not declared
there, only in the debug info for pck.ads. In other words,
there is no way that we accidently find "pck__t" by random chance.
I believe Pedro added a new function called ada_lookup_encoded_symbol
for that specific purpose, so I started by replacing the lookup
by language above by this. Unfortunately, still no joy.
This was because, even though ada_lookup_encoded_symbol puts angle-
brackets around the search name to signal that we want a verbatim
search, we end up losing that information in the function called
to compare a symbol with the search name:
| static bool
| do_full_match (const char *symbol_search_name,
| const lookup_name_info &lookup_name,
| completion_match_result *comp_match_res)
| {
| return full_match (symbol_search_name, ada_lookup_name (lookup_name));
^^^^^^^^^^^^^^^
|
<=> lookup_name.m_ada.m_encoded_name
(no angle brackets)
The way I fixed this was by introducing a new function called
do_exact_match, and then adjust ada_get_symbol_name_matcher to
return that function when seeing that we have a verbatim non-wild-match
search.
As it happens, this fixes an incorrect test in gdb.ada/homony.exp,
where we were inserting a breakpoint on a symbol using the angle-brackets
notation, and got 2 locations for that breakpoint...
(gdb) b <homonym__get_value>
Breakpoint 1 at 0x4029fc: <homonym__get_value>. (2 locations)
... each location being in a different function:
(gdb) info break
Num Type Disp Enb Address What
1 breakpoint keep y <MULTIPLE>
1.1 y 0x00000000004029fc in homonym.get_value
at /[...]/homonym.adb:32
1.2 y 0x0000000000402a3a in homonym.get_value
at /[...]/homonym.adb:50
(gdb) x /i 0x00000000004029fc
0x4029fc <homonym__get_value+8>: movl $0x1d,-0x4(%rbp)
(gdb) x /i 0x0000000000402a3a
0x402a3a <homonym__get_value__2+8>: movl $0x11,-0x4(%rbp)
Since we used angle-brackets, we shouldn't be matching the second one,
something this patch fixes.
gdb/ChangeLog:
* ada-lang.c (standard_lookup): Use ada_lookup_encoded_symbol
instead of lookup_symbol_in_language
(do_exact_match): New function.
(ada_get_symbol_name_matcher): Return do_exact_match when
doing a verbatim match.
gdb/testsuite/ChangeLog:
* gdb.ada/big_packed_array: New testcase.
* gdb.ada/homonym.exp: Fix incorrect expected output for
"break <homonym__get_value>" test.
Tested on x86_64-linux.
This commit is contained in:
Joel Brobecker
parent
aa9e1dc0c6
commit
a2cd4f1475
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@ -1,3 +1,11 @@
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2019-02-17 Joel Brobecker <brobecker@adacore.com>
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* ada-lang.c (standard_lookup): Use ada_lookup_encoded_symbol
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instead of lookup_symbol_in_language
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(do_exact_match): New function.
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(ada_get_symbol_name_matcher): Return do_exact_match when
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doing a verbatim match.
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2019-02-15 Tom Tromey <tromey@adacore.com>
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* ravenscar-thread.c (ravenscar_thread_target::resume)
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@ -4760,7 +4760,7 @@ standard_lookup (const char *name, const struct block *block,
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if (lookup_cached_symbol (name, domain, &sym.symbol, NULL))
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return sym.symbol;
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sym = lookup_symbol_in_language (name, block, domain, language_c, 0);
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ada_lookup_encoded_symbol (name, block, domain, &sym);
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cache_symbol (name, domain, sym.symbol, sym.block);
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return sym.symbol;
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}
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@ -14175,6 +14175,16 @@ do_full_match (const char *symbol_search_name,
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return full_match (symbol_search_name, ada_lookup_name (lookup_name));
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}
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/* symbol_name_matcher_ftype for exact (verbatim) matches. */
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static bool
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do_exact_match (const char *symbol_search_name,
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const lookup_name_info &lookup_name,
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completion_match_result *comp_match_res)
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{
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return strcmp (symbol_search_name, ada_lookup_name (lookup_name)) == 0;
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}
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/* Build the Ada lookup name for LOOKUP_NAME. */
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ada_lookup_name_info::ada_lookup_name_info (const lookup_name_info &lookup_name)
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@ -14285,6 +14295,8 @@ ada_get_symbol_name_matcher (const lookup_name_info &lookup_name)
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{
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if (lookup_name.ada ().wild_match_p ())
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return do_wild_match;
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else if (lookup_name.ada ().verbatim_p ())
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return do_exact_match;
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else
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return do_full_match;
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}
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@ -1,3 +1,9 @@
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2019-02-17 Joel Brobecker <brobecker@adacore.com>
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* gdb.ada/big_packed_array: New testcase.
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* gdb.ada/homonym.exp: Fix incorrect expected output for
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"break <homonym__get_value>" test.
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2019-02-13 Weimin Pan <weimin.pan@oracle.com>
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PR breakpoints/21870
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@ -0,0 +1,35 @@
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# Copyright 2019 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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if { [skip_ada_tests] } { return -1 }
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standard_ada_testfile foo_ra24_010
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if {[gdb_compile_ada "${srcfile}" "${binfile}" executable {debug}] != ""} {
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return -1
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}
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clean_restart ${testfile}
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set bp_location [gdb_get_line_number "STOP" ${testdir}/foo_ra24_010.adb]
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runto "foo_ra24_010.adb:$bp_location"
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gdb_test "print good" \
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"= \\(false <repeats 196 times>\\)" \
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gdb_test "print bad" \
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"= \\(false <repeats 196 times>\\)" \
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@ -0,0 +1,24 @@
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-- Copyright 2019 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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with Pck; use Pck;
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procedure Foo_RA24_010 is
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Good : PA := (others => False);
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Bad : Bad_Packed_Table := (others => False);
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begin
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Do_Nothing (Good'Address); -- STOP
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Do_Nothing (Bad'Address);
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end Foo_RA24_010;
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@ -0,0 +1,21 @@
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-- Copyright 2019 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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package body Pck is
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procedure Do_Nothing (A : System.Address) is
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begin
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null;
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end Do_Nothing;
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end Pck;
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@ -0,0 +1,53 @@
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-- Copyright 2019 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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with System;
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package Pck is
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type Enum_Idx is
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(e_000, e_001, e_002, e_003, e_004, e_005, e_006, e_007, e_008,
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e_009, e_010, e_011, e_012, e_013, e_014, e_015, e_016, e_017,
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e_018, e_019, e_020, e_021, e_022, e_023, e_024, e_025, e_026,
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e_027, e_028, e_029, e_030, e_031, e_032, e_033, e_034, e_035,
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e_036, e_037, e_038, e_039, e_040, e_041, e_042, e_043, e_044,
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e_045, e_046, e_047, e_048, e_049, e_050, e_051, e_052, e_053,
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e_054, e_055, e_056, e_057, e_058, e_059, e_060, e_061, e_062,
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e_063, e_064, e_065, e_066, e_067, e_068, e_069, e_070, e_071,
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e_072, e_073, e_074, e_075, e_076, e_077, e_078, e_079, e_080,
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e_081, e_082, e_083, e_084, e_085, e_086, e_087, e_088, e_089,
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e_090, e_091, e_092, e_093, e_094, e_095, e_096, e_097, e_098,
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e_099, e_100, e_101, e_102, e_103, e_104, e_105, e_106, e_107,
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e_108, e_109, e_110, e_111, e_112, e_113, e_114, e_115, e_116,
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e_117, e_118, e_119, e_120, e_121, e_122, e_123, e_124, e_125,
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e_126, e_127, e_128, e_129, e_130, e_131, e_132, e_133, e_134,
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e_135, e_136, e_137, e_138, e_139, e_140, e_141, e_142, e_143,
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e_144, e_145, e_146, e_147, e_148, e_149, e_150, e_151, e_152,
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e_153, e_154, e_155, e_156, e_157, e_158, e_159, e_160, e_161,
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e_162, e_163, e_164, e_165, e_166, e_167, e_168, e_169, e_170,
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e_171, e_172, e_173, e_174, e_175, e_176, e_177, e_178, e_179,
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e_180, e_181, e_182, e_183, e_184, e_185, e_186, e_187, e_188,
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e_189, e_190, e_191, e_192, e_193, e_194, e_195);
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type PA is array (Enum_Idx) of Boolean;
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pragma Pack (PA);
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type T is array (Enum_Idx) of Boolean;
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pragma Pack (T);
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T_Empty : constant T := (others => False);
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type Bad_Packed_Table is new T;
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Procedure Do_Nothing (A : System.Address);
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end Pck;
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@ -36,7 +36,7 @@ gdb_test "break homonym.adb:Get_Value" \
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"set breakpoint at homonym.adb:Get_Value"
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gdb_test "break <homonym__get_value>" \
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"Breakpoint \[0-9\]+ at $hex: <homonym__get_value>. .2 locations." \
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"Breakpoint \[0-9\]+ at $hex: file .*homonym\\.adb, line $decimal\\." \
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"set breakpoint at <homonym__get_value>"
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delete_breakpoints
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