[RFA/commit] (Ada) fix GDB crash printing packed array
Pedro Franco de Carvalho
pedromfc@linux.ibm.com
Fri May 10 20:51:00 GMT 2019
Hello,
I was running some regression tests for gdb 8.3, and I noticed that
there was a regression introduced by this patch for test
gdb.ada/pckd_arr_ren.exp.
I tried investigating, and it seems that this happened due to the
compiler in my system being relatively old (GNAT 4.9.3). I don't know
much about Ada, so I couldn't figure out if this is an issue with the
debug symbols generated by the older compiler or if GDB should handle
this, but it worked before the patch.
This is the relevant output from the test:
(gdb) break foo.adb:22
Breakpoint 1 at 0x10002410: file /home/pedromfc/binutils-gdb/gdb/testsuite/gdb.ada/pckd_arr_ren/foo.adb, line 22.
(gdb) run
Starting program: /home/pedromfc/binutils-gdb/build-bisect/gdb/testsuite/outputs/gdb.ada/pckd_arr_ren/foo
Breakpoint 1, foo () at /home/pedromfc/binutils-gdb/gdb/testsuite/gdb.ada/pckd_arr_ren/foo.adb:22
22 Do_Nothing (A2'Address); -- STOP
(gdb) print A2
Could not find renamed variable: a1
(gdb) FAIL: gdb.ada/pckd_arr_ren.exp: print var
That error message seems to come from ada-exp.y:write_object_renaming.
Thanks!
--
Pedro Franco de Carvalho
Joel Brobecker <brobecker@adacore.com> writes:
> 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
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