[PATCH 1/5] [gdb/testsuite] Add gdb.dwarf2/enum-type-c++.exp, regression test for PR31900.

Mon Sep 16 19:21:02 GMT 2024

On 9/12/24 8:52 AM, Tom de Vries wrote:
> Consider the following test-case:
> ...
> $ cat a.h
> namespace ns {
>
> class A {
> public:
>    enum {
>      val1 = 1
>    };
> };
>
> }
> $ cat main.c
>
> ns::A a;
>
> int
> main (void)
> {
>    return 0;
> }
> $ cat val1.c
>
> int u1 = ns::A::val1;
> ...
> compiled with debug info:
> ...
> $ g++ main.c val1.c -g
> ...
>
> When trying to print ns::A::val with current trunk and gdb 15.1 we get:
> ...
> $ gdb -q -batch a.out -ex "print ns::A::val1"
> There is no field named val1
> ...
>
> This PR c++/31900.
>
> With gdb 14.2 we get the expected:
> ...
> $ gdb -q -batch a.out -ex "print ns::A::val1"
> $1 = ns::A::val1
> ...
>
> This is a regression since commit 4e417d7bb1c ("Change handling of
> DW_TAG_enumeration_type in DWARF scanner").
>
> Reverting the commit on current trunk fixes the problem.
>
> So how does this problem happen?
>
> First, let's consider the current trunk, with the commit reverted.
>
> Gdb looks for the entry ns::A::val1, and find this entry:
> ...
>      [29] ((cooked_index_entry *) 0x7f7830002ef0)
>      name:       val1
>      canonical:  val1
>      qualified:  ns::A::val1
>      DWARF tag:  DW_TAG_enumerator
>      flags:      0x0 []
>      DIE offset: 0x15a
>      parent:     ((cooked_index_entry *) 0x7f7830002ec0) [A]
> ...
> and expands the corresponding CU val1.c containing this debug info:
> ...
>   <2><14a>: Abbrev Number: 3 (DW_TAG_class_type)
>      <14b>   DW_AT_name        : A
>      <14d>   DW_AT_byte_size   : 1
>   <3><150>: Abbrev Number: 4 (DW_TAG_enumeration_type)
>      <151>   DW_AT_encoding    : 7       (unsigned)
>      <152>   DW_AT_byte_size   : 4
>      <153>   DW_AT_type        : <0x163>
>      <159>   DW_AT_accessibility: 1      (public)
>   <4><15a>: Abbrev Number: 5 (DW_TAG_enumerator)
>      <15b>   DW_AT_name        : val1
>      <15f>   DW_AT_const_value : 1
>   <4><160>: Abbrev Number: 0
>   <3><161>: Abbrev Number: 0
>   <2><162>: Abbrev Number: 0
> ...
> after which it finds ns::A::val1 in the expanded symtabs.
>
> Now let's consider the current trunk as is (so, with the commit present).
>
> Gdb looks for the entry ns::A::val1, but doesn't find it because the val1
> entry is missing its parent:
> ...
>     [29] ((cooked_index_entry *) 0x7f5240002ef0)
>      name:       val1
>      canonical:  val1
>      qualified:  val1
>      DWARF tag:  DW_TAG_enumerator
>      flags:      0x0 []
>      DIE offset: 0x15a
>      parent:     ((cooked_index_entry *) 0)
> ...
>
> Then gdb looks for the entry ns::A, and finds this entry:
> ...
>     [3] ((cooked_index_entry *) 0x7f5248002ec0)
>      name:       A
>      canonical:  A
>      qualified:  ns::A
>      DWARF tag:  DW_TAG_class_type
>      flags:      0x0 []
>      DIE offset: 0xdd
>      parent:     ((cooked_index_entry *) 0x7f5248002e90) [ns]
> ...
> which corresponds to this debug info, which doesn't contain val1
> due to -fno-eliminate-unused-debug-types:
> ...
>   <2><dd>: Abbrev Number: 3 (DW_TAG_class_type)
>      <de>   DW_AT_name        : A
>      <e0>   DW_AT_byte_size   : 1
>   <2><e3>: Abbrev Number: 0
> ...
>
> Gdb expands the corresponding CU main.c, after which it doesn't find
> ns::A::val1 in the expanded symtabs.
>
> The root cause of the problem is the missing parent on the val1
> cooked_index_entry, but this only becomes user-visible through the
> elaborate scenario above.
>
> Add a test-case gdb.dwarf2/enum-type-c++.exp that contains a regression test
> for this problem that doesn't rely on expansion state or
> -feliminate-unused-debug-types, but simply tests for the root cause by
> grepping for ns::A::val1 in the output of "maint print objfile".
>
> Tested on x86_64-linux.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31900
> ---
>   gdb/testsuite/gdb.dwarf2/enum-type-c++.cc  | 29 ++++++++++++++
>   gdb/testsuite/gdb.dwarf2/enum-type-c++.exp | 44 ++++++++++++++++++++++
>   2 files changed, 73 insertions(+)
>   create mode 100644 gdb/testsuite/gdb.dwarf2/enum-type-c++.cc
>   create mode 100644 gdb/testsuite/gdb.dwarf2/enum-type-c++.exp
>
> diff --git a/gdb/testsuite/gdb.dwarf2/enum-type-c++.cc b/gdb/testsuite/gdb.dwarf2/enum-type-c++.cc
> new file mode 100644
> index 00000000000..c0ffaad0316
> --- /dev/null
> +++ b/gdb/testsuite/gdb.dwarf2/enum-type-c++.cc
> @@ -0,0 +1,29 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2024 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/>.  */
> +
> +namespace ns {
> +
> +class A {
> +public:
> +  enum {
> +    val1 = 1
> +  };
> +};
> +
> +}
> +
> +int u1 = ns::A::val1;
> diff --git a/gdb/testsuite/gdb.dwarf2/enum-type-c++.exp b/gdb/testsuite/gdb.dwarf2/enum-type-c++.exp
> new file mode 100644
> index 00000000000..44ad225de02
> --- /dev/null
> +++ b/gdb/testsuite/gdb.dwarf2/enum-type-c++.exp
> @@ -0,0 +1,44 @@
> +# Copyright 2024 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/>.
> +
> +require !readnow
> +
> +load_lib dwarf.exp
> +
> +# This test can only be run on targets which support DWARF-2 and use gas.
> +require dwarf2_support
> +
> +standard_testfile main.c .cc
> +
> +if { [prepare_for_testing "failed to prepare" $testfile \
> +	  [list $srcfile $srcfile2] {debug c++}] } {
> +    return -1
> +}
> +
> +require {string equal [have_index $binfile] ""}
> +
> +set re_ws "\[ \t\]"
> +
> +# Regression test for PR31900.
> +setup_kfail "gdb/31900" *-*-*
> +set val1 ns::A::val1
> +gdb_test_lines "maint print objfiles" \
> +    "val1 has a parent" \
> +    [multi_line \
> +	 "" \
> +	 "$re_ws+qualified:$re_ws+$val1" \
> +	 ".*"]
> +
> +gdb_test "print $val1" " = $val1"
>
> base-commit: 4290b2c07e2d9bc1e1661a4ad5e343e3eb307770

Hi Tom

The test introduced by this patch fails with clang with the attached log.

Some of the fails come from later patches, but "print ns::A::val1" fails 
ever since this patch.

-- 
Cheers,
Guinevere Larsen
She/Her/Hers
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