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g++ 11.1.0 has a bug where it will emit a negative
DW_AT_data_member_location in some cases:
$ cat test.cpp
#include <memory>
int
main()
{
std::unique_ptr<int> ptr;
}
$ g++ -g test.cpp
$ llvm-dwarfdump -F a.out
...
0x00000964: DW_TAG_member
DW_AT_name [DW_FORM_strp] ("_M_head_impl")
DW_AT_decl_file [DW_FORM_data1] ("/usr/include/c++/11.1.0/tuple")
DW_AT_decl_line [DW_FORM_data1] (125)
DW_AT_decl_column [DW_FORM_data1] (0x27)
DW_AT_type [DW_FORM_ref4] (0x0000067a "default_delete<int>")
DW_AT_data_member_location [DW_FORM_sdata] (-1)
...
This leads to a GDB crash (when built with ASan, otherwise probably
garbage results), since it tries to read just before (to the left, in
ASan speak) of the value's buffer:
==888645==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6020000c52af at pc 0x7f711b239f4b bp 0x7fff356bd470 sp 0x7fff356bcc18
READ of size 1 at 0x6020000c52af thread T0
#0 0x7f711b239f4a in __interceptor_memcpy /build/gcc/src/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827
#1 0x555c4977efa1 in value_contents_copy_raw /home/simark/src/binutils-gdb/gdb/value.c:1347
#2 0x555c497909cd in value_primitive_field(value*, long, int, type*) /home/simark/src/binutils-gdb/gdb/value.c:3126
#3 0x555c478f2eaa in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:333
#4 0x555c478f63b2 in cp_print_value /home/simark/src/binutils-gdb/gdb/cp-valprint.c:513
#5 0x555c478f02ca in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:161
#6 0x555c478f63b2 in cp_print_value /home/simark/src/binutils-gdb/gdb/cp-valprint.c:513
#7 0x555c478f02ca in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:161
#8 0x555c478f63b2 in cp_print_value /home/simark/src/binutils-gdb/gdb/cp-valprint.c:513
#9 0x555c478f02ca in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:161
#10 0x555c4760d45f in c_value_print_struct /home/simark/src/binutils-gdb/gdb/c-valprint.c:383
#11 0x555c4760df4c in c_value_print_inner(value*, ui_file*, int, value_print_options const*) /home/simark/src/binutils-gdb/gdb/c-valprint.c:438
#12 0x555c483ff9a7 in language_defn::value_print_inner(value*, ui_file*, int, value_print_options const*) const /home/simark/src/binutils-gdb/gdb/language.c:632
#13 0x555c49758b68 in do_val_print /home/simark/src/binutils-gdb/gdb/valprint.c:1048
#14 0x555c49759b17 in common_val_print(value*, ui_file*, int, value_print_options const*, language_defn const*) /home/simark/src/binutils-gdb/gdb/valprint.c:1151
#15 0x555c478f2fcb in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:335
#16 0x555c478f63b2 in cp_print_value /home/simark/src/binutils-gdb/gdb/cp-valprint.c:513
#17 0x555c478f02ca in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:161
#18 0x555c4760d45f in c_value_print_struct /home/simark/src/binutils-gdb/gdb/c-valprint.c:383
#19 0x555c4760df4c in c_value_print_inner(value*, ui_file*, int, value_print_options const*) /home/simark/src/binutils-gdb/gdb/c-valprint.c:438
#20 0x555c483ff9a7 in language_defn::value_print_inner(value*, ui_file*, int, value_print_options const*) const /home/simark/src/binutils-gdb/gdb/language.c:632
#21 0x555c49758b68 in do_val_print /home/simark/src/binutils-gdb/gdb/valprint.c:1048
#22 0x555c49759b17 in common_val_print(value*, ui_file*, int, value_print_options const*, language_defn const*) /home/simark/src/binutils-gdb/gdb/valprint.c:1151
#23 0x555c478f2fcb in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:335
#24 0x555c4760d45f in c_value_print_struct /home/simark/src/binutils-gdb/gdb/c-valprint.c:383
#25 0x555c4760df4c in c_value_print_inner(value*, ui_file*, int, value_print_options const*) /home/simark/src/binutils-gdb/gdb/c-valprint.c:438
#26 0x555c483ff9a7 in language_defn::value_print_inner(value*, ui_file*, int, value_print_options const*) const /home/simark/src/binutils-gdb/gdb/language.c:632
#27 0x555c49758b68 in do_val_print /home/simark/src/binutils-gdb/gdb/valprint.c:1048
#28 0x555c49759b17 in common_val_print(value*, ui_file*, int, value_print_options const*, language_defn const*) /home/simark/src/binutils-gdb/gdb/valprint.c:1151
#29 0x555c4760f04c in c_value_print(value*, ui_file*, value_print_options const*) /home/simark/src/binutils-gdb/gdb/c-valprint.c:587
#30 0x555c483ff954 in language_defn::value_print(value*, ui_file*, value_print_options const*) const /home/simark/src/binutils-gdb/gdb/language.c:614
#31 0x555c49759f61 in value_print(value*, ui_file*, value_print_options const*) /home/simark/src/binutils-gdb/gdb/valprint.c:1189
#32 0x555c48950f70 in print_formatted /home/simark/src/binutils-gdb/gdb/printcmd.c:337
#33 0x555c48958eda in print_value(value*, value_print_options const&) /home/simark/src/binutils-gdb/gdb/printcmd.c:1258
#34 0x555c48959891 in print_command_1 /home/simark/src/binutils-gdb/gdb/printcmd.c:1367
#35 0x555c4895a3df in print_command /home/simark/src/binutils-gdb/gdb/printcmd.c:1458
#36 0x555c4767f974 in do_simple_func /home/simark/src/binutils-gdb/gdb/cli/cli-decode.c:97
#37 0x555c47692e25 in cmd_func(cmd_list_element*, char const*, int) /home/simark/src/binutils-gdb/gdb/cli/cli-decode.c:2475
#38 0x555c4936107e in execute_command(char const*, int) /home/simark/src/binutils-gdb/gdb/top.c:670
#39 0x555c485f1bff in catch_command_errors /home/simark/src/binutils-gdb/gdb/main.c:523
#40 0x555c485f249c in execute_cmdargs /home/simark/src/binutils-gdb/gdb/main.c:618
#41 0x555c485f6677 in captured_main_1 /home/simark/src/binutils-gdb/gdb/main.c:1317
#42 0x555c485f6c83 in captured_main /home/simark/src/binutils-gdb/gdb/main.c:1338
#43 0x555c485f6d65 in gdb_main(captured_main_args*) /home/simark/src/binutils-gdb/gdb/main.c:1363
#44 0x555c46e41ba8 in main /home/simark/src/binutils-gdb/gdb/gdb.c:32
#45 0x7f71198bcb24 in __libc_start_main (/usr/lib/libc.so.6+0x27b24)
#46 0x555c46e4197d in _start (/home/simark/build/binutils-gdb-one-target/gdb/gdb+0x77f197d)
0x6020000c52af is located 1 bytes to the left of 8-byte region [0x6020000c52b0,0x6020000c52b8)
allocated by thread T0 here:
#0 0x7f711b2b7459 in __interceptor_calloc /build/gcc/src/gcc/libsanitizer/asan/asan_malloc_linux.cpp:154
#1 0x555c470acdc9 in xcalloc /home/simark/src/binutils-gdb/gdb/alloc.c:100
#2 0x555c49b775cd in xzalloc(unsigned long) /home/simark/src/binutils-gdb/gdbsupport/common-utils.cc:29
#3 0x555c4977bdeb in allocate_value_contents /home/simark/src/binutils-gdb/gdb/value.c:1029
#4 0x555c4977be25 in allocate_value(type*) /home/simark/src/binutils-gdb/gdb/value.c:1040
#5 0x555c4979030d in value_primitive_field(value*, long, int, type*) /home/simark/src/binutils-gdb/gdb/value.c:3092
#6 0x555c478f6280 in cp_print_value /home/simark/src/binutils-gdb/gdb/cp-valprint.c:501
#7 0x555c478f02ca in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:161
#8 0x555c478f63b2 in cp_print_value /home/simark/src/binutils-gdb/gdb/cp-valprint.c:513
#9 0x555c478f02ca in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:161
#10 0x555c478f63b2 in cp_print_value /home/simark/src/binutils-gdb/gdb/cp-valprint.c:513
#11 0x555c478f02ca in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:161
#12 0x555c4760d45f in c_value_print_struct /home/simark/src/binutils-gdb/gdb/c-valprint.c:383
#13 0x555c4760df4c in c_value_print_inner(value*, ui_file*, int, value_print_options const*) /home/simark/src/binutils-gdb/gdb/c-valprint.c:438
#14 0x555c483ff9a7 in language_defn::value_print_inner(value*, ui_file*, int, value_print_options const*) const /home/simark/src/binutils-gdb/gdb/language.c:632
#15 0x555c49758b68 in do_val_print /home/simark/src/binutils-gdb/gdb/valprint.c:1048
#16 0x555c49759b17 in common_val_print(value*, ui_file*, int, value_print_options const*, language_defn const*) /home/simark/src/binutils-gdb/gdb/valprint.c:1151
#17 0x555c478f2fcb in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:335
#18 0x555c478f63b2 in cp_print_value /home/simark/src/binutils-gdb/gdb/cp-valprint.c:513
#19 0x555c478f02ca in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:161
#20 0x555c4760d45f in c_value_print_struct /home/simark/src/binutils-gdb/gdb/c-valprint.c:383
#21 0x555c4760df4c in c_value_print_inner(value*, ui_file*, int, value_print_options const*) /home/simark/src/binutils-gdb/gdb/c-valprint.c:438
#22 0x555c483ff9a7 in language_defn::value_print_inner(value*, ui_file*, int, value_print_options const*) const /home/simark/src/binutils-gdb/gdb/language.c:632
#23 0x555c49758b68 in do_val_print /home/simark/src/binutils-gdb/gdb/valprint.c:1048
#24 0x555c49759b17 in common_val_print(value*, ui_file*, int, value_print_options const*, language_defn const*) /home/simark/src/binutils-gdb/gdb/valprint.c:1151
#25 0x555c478f2fcb in cp_print_value_fields(value*, ui_file*, int, value_print_options const*, type**, int) /home/simark/src/binutils-gdb/gdb/cp-valprint.c:335
#26 0x555c4760d45f in c_value_print_struct /home/simark/src/binutils-gdb/gdb/c-valprint.c:383
#27 0x555c4760df4c in c_value_print_inner(value*, ui_file*, int, value_print_options const*) /home/simark/src/binutils-gdb/gdb/c-valprint.c:438
#28 0x555c483ff9a7 in language_defn::value_print_inner(value*, ui_file*, int, value_print_options const*) const /home/simark/src/binutils-gdb/gdb/language.c:632
#29 0x555c49758b68 in do_val_print /home/simark/src/binutils-gdb/gdb/valprint.c:1048
Since there are some binaries with this in the wild, I think it would be
useful for GDB to work around this. I did the obvious simple thing, if
the DW_AT_data_member_location's value is -1, replace it with 0. I
added a producer check to only apply this fixup for GCC 11. The idea is
that if some other compiler ever uses a DW_AT_data_member_location value
of -1 by mistake, we don't know (before analyzing the bug at least) if
they did mean 0 or some other value. So I wouldn't want to apply the
fixup in that case.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28063
Change-Id: Ieef3459b0b9bbce8bdad838ba83b4b64e7269d42
78 lines
2.1 KiB
Plaintext
78 lines
2.1 KiB
Plaintext
# Copyright 2021-2022 Free Software Foundation, Inc.
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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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# Test our workaround for a GCC 11 bug, where it sometimes puts a -1 value for
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# DW_AT_data_member_location:
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#
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# Negative DW_AT_data_member_location
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# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101378
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load_lib dwarf.exp
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# This test can only be run on targets which support DWARF-2 and use gas.
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if { ![dwarf2_support] } {
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return 0
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}
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standard_testfile .c -dw.S
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set asm_file [standard_output_file ${srcfile2}]
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Dwarf::assemble ${asm_file} {
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cu {} {
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DW_TAG_compile_unit {
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{DW_AT_language @DW_LANG_C99}
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{DW_AT_producer "GNU C++17 11.1.0 -mtune=generic -march=x86-64 -g3 -O0"}
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{name ${::srcfile}}
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} {
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declare_labels int_label struct_label
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int_label: DW_TAG_base_type {
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{DW_AT_byte_size 4 DW_FORM_udata}
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{DW_AT_encoding @DW_ATE_signed}
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{DW_AT_name "int"}
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}
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struct_label: DW_TAG_structure_type {
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{DW_AT_name "the_struct"}
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{DW_AT_byte_size 4 DW_FORM_udata}
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} {
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DW_TAG_member {
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{DW_AT_name "field"}
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{DW_AT_type :$int_label}
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{DW_AT_data_member_location -1 DW_FORM_sdata}
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}
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}
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DW_TAG_variable {
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{DW_AT_name "s"}
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{DW_AT_type :$struct_label}
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{DW_AT_location {DW_OP_addr [gdb_target_symbol "s"]} SPECIAL_expr}
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}
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}
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}
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}
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if { [prepare_for_testing "failed to prepare" ${testfile} [list $srcfile $asm_file] {nodebug}] } {
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return
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}
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if { ![runto_main] } {
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return
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}
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gdb_test "print /x s" " = {field = 0x11222211}"
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gdb_test "print /x s.field" " = 0x11222211"
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