This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
[RFA/commit] (Ada) fix GDB crash printing packed array
- From: Joel Brobecker <brobecker at adacore dot com>
- To: gdb-patches at sourceware dot org
- Date: Sun, 10 Feb 2019 03:21:41 -0500
- Subject: [RFA/commit] (Ada) fix GDB crash printing packed array
Hello,
This touches on symbol searching, and in particular the ability
to search for an exact match...
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. OK to commit?
Thanks,
--
Joel
---
gdb/ada-lang.c | 14 +++++-
gdb/testsuite/gdb.ada/big_packed_array.exp | 35 ++++++++++++++
.../gdb.ada/big_packed_array/foo_ra24_010.adb | 24 ++++++++++
gdb/testsuite/gdb.ada/big_packed_array/pck.adb | 21 +++++++++
gdb/testsuite/gdb.ada/big_packed_array/pck.ads | 53 ++++++++++++++++++++++
gdb/testsuite/gdb.ada/homonym.exp | 2 +-
6 files changed, 147 insertions(+), 2 deletions(-)
create mode 100644 gdb/testsuite/gdb.ada/big_packed_array.exp
create mode 100644 gdb/testsuite/gdb.ada/big_packed_array/foo_ra24_010.adb
create mode 100644 gdb/testsuite/gdb.ada/big_packed_array/pck.adb
create mode 100644 gdb/testsuite/gdb.ada/big_packed_array/pck.ads
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index a878d4d..415dc53 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -4760,7 +4760,7 @@ standard_lookup (const char *name, const struct block *block,
if (lookup_cached_symbol (name, domain, &sym.symbol, NULL))
return sym.symbol;
- sym = lookup_symbol_in_language (name, block, domain, language_c, 0);
+ ada_lookup_encoded_symbol (name, block, domain, &sym);
cache_symbol (name, domain, sym.symbol, sym.block);
return sym.symbol;
}
@@ -14193,6 +14193,16 @@ do_full_match (const char *symbol_search_name,
return full_match (symbol_search_name, ada_lookup_name (lookup_name));
}
+/* symbol_name_matcher_ftype for exact (verbatim) matches. */
+
+static bool
+do_exact_match (const char *symbol_search_name,
+ const lookup_name_info &lookup_name,
+ completion_match_result *comp_match_res)
+{
+ return strcmp (symbol_search_name, ada_lookup_name (lookup_name)) == 0;
+}
+
/* Build the Ada lookup name for LOOKUP_NAME. */
ada_lookup_name_info::ada_lookup_name_info (const lookup_name_info &lookup_name)
@@ -14303,6 +14313,8 @@ ada_get_symbol_name_matcher (const lookup_name_info &lookup_name)
{
if (lookup_name.ada ().wild_match_p ())
return do_wild_match;
+ else if (lookup_name.ada ().verbatim_p ())
+ return do_exact_match;
else
return do_full_match;
}
diff --git a/gdb/testsuite/gdb.ada/big_packed_array.exp b/gdb/testsuite/gdb.ada/big_packed_array.exp
new file mode 100644
index 0000000..a2e03bb
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/big_packed_array.exp
@@ -0,0 +1,35 @@
+# Copyright 2019 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/>.
+
+load_lib "ada.exp"
+
+if { [skip_ada_tests] } { return -1 }
+
+standard_ada_testfile foo_ra24_010
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable {debug}] != ""} {
+ return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/foo_ra24_010.adb]
+runto "foo_ra24_010.adb:$bp_location"
+
+gdb_test "print good" \
+ "= \\(false <repeats 196 times>\\)" \
+
+gdb_test "print bad" \
+ "= \\(false <repeats 196 times>\\)" \
diff --git a/gdb/testsuite/gdb.ada/big_packed_array/foo_ra24_010.adb b/gdb/testsuite/gdb.ada/big_packed_array/foo_ra24_010.adb
new file mode 100644
index 0000000..7e6a26c
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/big_packed_array/foo_ra24_010.adb
@@ -0,0 +1,24 @@
+-- Copyright 2019 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_RA24_010 is
+ Good : PA := (others => False);
+ Bad : Bad_Packed_Table := (others => False);
+begin
+ Do_Nothing (Good'Address); -- STOP
+ Do_Nothing (Bad'Address);
+end Foo_RA24_010;
diff --git a/gdb/testsuite/gdb.ada/big_packed_array/pck.adb b/gdb/testsuite/gdb.ada/big_packed_array/pck.adb
new file mode 100644
index 0000000..6535991
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/big_packed_array/pck.adb
@@ -0,0 +1,21 @@
+-- Copyright 2019 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/>.
+
+package body Pck is
+ procedure Do_Nothing (A : System.Address) is
+ begin
+ null;
+ end Do_Nothing;
+end Pck;
diff --git a/gdb/testsuite/gdb.ada/big_packed_array/pck.ads b/gdb/testsuite/gdb.ada/big_packed_array/pck.ads
new file mode 100644
index 0000000..18b58fb
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/big_packed_array/pck.ads
@@ -0,0 +1,53 @@
+-- Copyright 2019 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 System;
+
+package Pck is
+ type Enum_Idx is
+ (e_000, e_001, e_002, e_003, e_004, e_005, e_006, e_007, e_008,
+ e_009, e_010, e_011, e_012, e_013, e_014, e_015, e_016, e_017,
+ e_018, e_019, e_020, e_021, e_022, e_023, e_024, e_025, e_026,
+ e_027, e_028, e_029, e_030, e_031, e_032, e_033, e_034, e_035,
+ e_036, e_037, e_038, e_039, e_040, e_041, e_042, e_043, e_044,
+ e_045, e_046, e_047, e_048, e_049, e_050, e_051, e_052, e_053,
+ e_054, e_055, e_056, e_057, e_058, e_059, e_060, e_061, e_062,
+ e_063, e_064, e_065, e_066, e_067, e_068, e_069, e_070, e_071,
+ e_072, e_073, e_074, e_075, e_076, e_077, e_078, e_079, e_080,
+ e_081, e_082, e_083, e_084, e_085, e_086, e_087, e_088, e_089,
+ e_090, e_091, e_092, e_093, e_094, e_095, e_096, e_097, e_098,
+ e_099, e_100, e_101, e_102, e_103, e_104, e_105, e_106, e_107,
+ e_108, e_109, e_110, e_111, e_112, e_113, e_114, e_115, e_116,
+ e_117, e_118, e_119, e_120, e_121, e_122, e_123, e_124, e_125,
+ e_126, e_127, e_128, e_129, e_130, e_131, e_132, e_133, e_134,
+ e_135, e_136, e_137, e_138, e_139, e_140, e_141, e_142, e_143,
+ e_144, e_145, e_146, e_147, e_148, e_149, e_150, e_151, e_152,
+ e_153, e_154, e_155, e_156, e_157, e_158, e_159, e_160, e_161,
+ e_162, e_163, e_164, e_165, e_166, e_167, e_168, e_169, e_170,
+ e_171, e_172, e_173, e_174, e_175, e_176, e_177, e_178, e_179,
+ e_180, e_181, e_182, e_183, e_184, e_185, e_186, e_187, e_188,
+ e_189, e_190, e_191, e_192, e_193, e_194, e_195);
+
+ type PA is array (Enum_Idx) of Boolean;
+ pragma Pack (PA);
+
+ type T is array (Enum_Idx) of Boolean;
+ pragma Pack (T);
+ T_Empty : constant T := (others => False);
+
+ type Bad_Packed_Table is new T;
+
+ Procedure Do_Nothing (A : System.Address);
+end Pck;
diff --git a/gdb/testsuite/gdb.ada/homonym.exp b/gdb/testsuite/gdb.ada/homonym.exp
index 625a4d4..3888090 100644
--- a/gdb/testsuite/gdb.ada/homonym.exp
+++ b/gdb/testsuite/gdb.ada/homonym.exp
@@ -36,7 +36,7 @@ gdb_test "break homonym.adb:Get_Value" \
"set breakpoint at homonym.adb:Get_Value"
gdb_test "break <homonym__get_value>" \
- "Breakpoint \[0-9\]+ at $hex: <homonym__get_value>. .2 locations." \
+ "Breakpoint \[0-9\]+ at $hex: file .*homonym\\.adb, line $decimal\\." \
"set breakpoint at <homonym__get_value>"
delete_breakpoints
--
2.1.4