Re: [PATCH][gdb/symtab] Fix "file index out of range" complaint

Tom de Vries via Gdb-patches
2022-09-17T06:32:37Z

On 9/9/22 08:51, Tom de Vries wrote:
> Hi,
>
> With the test-case included in this commit, we run into this FAIL:
> ...
> (gdb) p var^M
> During symbol reading: file index out of range^M
> $1 = 0^M
> (gdb) FAIL: gdb.dwarf2/dw2-no-code-cu.exp: p var with no complaints
> ...
>
> This is a regression since commit 6d263fe46e0 ("Avoid bad breakpoints with
> --gc-sections"), which contains this change in read_file_scope:
> ...
> - handle_DW_AT_stmt_list (die, cu, fnd, lowpc);
> + if (lowpc != highpc)
> + handle_DW_AT_stmt_list (die, cu, fnd, lowpc);
> ...
>
> The change intends to avoid a problem with a check in
> lnp_state_machine::check_line_address, but also prevents the file and dir
> tables from being read, which causes the complaint.
>
> Fix the FAIL by reducing the scope of the "lowpc != highpc" condition to the
> call to dwarf_decode_lines in handle_DW_AT_stmt_list.
>
> Tested on x86_64-linux.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29561
>
> Any comments?
>

Committed.

Thanks,
- Tom
>
> [gdb/symtab] Fix "file index out of range" complaint
>
> ---
> gdb/dwarf2/read.c | 20 +++++++++----------
> gdb/testsuite/gdb.dwarf2/dw2-no-code-cu.c | 18 +++++++++++++++++
> gdb/testsuite/gdb.dwarf2/dw2-no-code-cu.exp | 31 +++++++++++++++++++++++++++++
> 3 files changed, 59 insertions(+), 10 deletions(-)
>
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index 3ca441c4cae..e86cc83b6f1 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -9495,8 +9495,8 @@ find_file_and_directory (struct die_info *die, struct dwarf2_cu *cu)
>
> static void
> handle_DW_AT_stmt_list (struct die_info *die, struct dwarf2_cu *cu,
> - const file_and_directory &fnd,
> - CORE_ADDR lowpc) /* ARI: editCase function */
> + const file_and_directory &fnd, CORE_ADDR lowpc,
> + bool have_code) /* ARI: editCase function */
> {
> dwarf2_per_objfile *per_objfile = cu->per_objfile;
> struct attribute *attr;
> @@ -9583,7 +9583,12 @@ handle_DW_AT_stmt_list (struct die_info *die, struct dwarf2_cu *cu,
> gdb_assert (die->tag != DW_TAG_partial_unit);
> }
> decode_mapping = (die->tag != DW_TAG_partial_unit);
> - dwarf_decode_lines (cu->line_header, cu, lowpc, decode_mapping);
> + /* The have_code check is here because, if LOWPC and HIGHPC are both 0x0,
> + then there won't be any interesting code in the CU, but a check later on
> + (in lnp_state_machine::check_line_address) will fail to properly exclude
> + an entry that was removed via --gc-sections. */
> + if (have_code)
> + dwarf_decode_lines (cu->line_header, cu, lowpc, decode_mapping);
> }
>
> /* Process DW_TAG_compile_unit or DW_TAG_partial_unit. */
> @@ -9622,13 +9627,8 @@ read_file_scope (struct die_info *die, struct dwarf2_cu *cu)
>
> /* Decode line number information if present. We do this before
> processing child DIEs, so that the line header table is available
> - for DW_AT_decl_file. The PC check is here because, if LOWPC and
> - HIGHPC are both 0x0, then there won't be any interesting code in
> - the CU, but a check later on (in
> - lnp_state_machine::check_line_address) will fail to properly
> - exclude an entry that was removed via --gc-sections. */
> - if (lowpc != highpc)
> - handle_DW_AT_stmt_list (die, cu, fnd, lowpc);
> + for DW_AT_decl_file. */
> + handle_DW_AT_stmt_list (die, cu, fnd, lowpc, lowpc != highpc);
>
> /* Process all dies in compilation unit. */
> if (die->child != NULL)
> diff --git a/gdb/testsuite/gdb.dwarf2/dw2-no-code-cu.c b/gdb/testsuite/gdb.dwarf2/dw2-no-code-cu.c
> new file mode 100644
> index 00000000000..576b1a21442
> --- /dev/null
> +++ b/gdb/testsuite/gdb.dwarf2/dw2-no-code-cu.c
> @@ -0,0 +1,18 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> + Copyright 2022 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/>. */
> +
> +int var;
> diff --git a/gdb/testsuite/gdb.dwarf2/dw2-no-code-cu.exp b/gdb/testsuite/gdb.dwarf2/dw2-no-code-cu.exp
> new file mode 100644
> index 00000000000..911bb7e2a7d
> --- /dev/null
> +++ b/gdb/testsuite/gdb.dwarf2/dw2-no-code-cu.exp
> @@ -0,0 +1,31 @@
> +# Copyright 2022 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/>.
> +
> +standard_testfile .c main.c
> +
> +if [prepare_for_testing "failed to prepare" $testfile "$srcfile $srcfile2"] {
> + return -1
> +}
> +
> +set cmd "p var"
> +
> +set re \
> + [multi_line \
> + "$cmd" \
> + "\\\$1 = 0"]
> +
> +with_complaints 5 {
> + gdb_test $cmd $re "$cmd with no complaints"
> +}