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Kevin Buettner a640adf7cf Test case reproducing PR28030 bug
The original reproducer for PR28030 required use of a specific
compiler version - gcc-c++-11.1.1-3.fc34 is mentioned in the PR,
though it seems probable that other gcc versions might also be able to
reproduce the bug as well.  This commit introduces a test case which,
using the DWARF assembler, provides a reproducer which is independent
of the compiler version.  (Well, it'll work with whatever compilers
the DWARF assembler works with.)

To the best of my knowledge, it's also the first test case which uses
the DWARF assembler to provide debug info for a shared object.  That
being the case, I provided more than the usual commentary which should
allow this case to be used as a template when a combo shared
library / DWARF assembler test case is required in the future.

I provide some details regarding the bug in a comment near the
beginning of locexpr-dml.exp.

This problem was difficult to reproduce; I found myself constantly
referring to the backtrace while trying to figure out what (else) I
might be missing while trying to create a reproducer.  Below is a
partial backtrace which I include for posterity.

 #0  internal_error (
    file=0xc50110 "/ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/gdbtypes.c", line=5575,
    fmt=0xc520c0 "Unexpected type field location kind: %d")
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdbsupport/errors.cc:51
 #1  0x00000000006ef0c5 in copy_type_recursive (objfile=0x1635930,
    type=0x274c260, copied_types=0x30bb290)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/gdbtypes.c:5575
 #2  0x00000000006ef382 in copy_type_recursive (objfile=0x1635930,
    type=0x274ca10, copied_types=0x30bb290)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/gdbtypes.c:5602
 #3  0x0000000000a7409a in preserve_one_value (value=0x24269f0,
    objfile=0x1635930, copied_types=0x30bb290)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/value.c:2529
 #4  0x000000000072012a in gdbscm_preserve_values (
    extlang=0xc55720 <extension_language_guile>, objfile=0x1635930,
    copied_types=0x30bb290)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/guile/scm-value.c:94
 #5  0x00000000006a3f82 in preserve_ext_lang_values (objfile=0x1635930,
    copied_types=0x30bb290)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/extension.c:568
 #6  0x0000000000a7428d in preserve_values (objfile=0x1635930)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/value.c:2579
 #7  0x000000000082d514 in objfile::~objfile (this=0x1635930,
    __in_chrg=<optimized out>)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/objfiles.c:549
 #8  0x0000000000831cc8 in std::_Sp_counted_ptr<objfile*, (__gnu_cxx::_Lock_policy)2>::_M_dispose (this=0x1654580)
    at /usr/include/c++/11/bits/shared_ptr_base.h:348
 #9  0x00000000004e6617 in std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release (this=0x1654580) at /usr/include/c++/11/bits/shared_ptr_base.h:168
 #10 0x00000000004e1d2f in std::__shared_count<(__gnu_cxx::_Lock_policy)2>::~__shared_count (this=0x190bb88, __in_chrg=<optimized out>)
    at /usr/include/c++/11/bits/shared_ptr_base.h:705
 #11 0x000000000082feee in std::__shared_ptr<objfile, (__gnu_cxx::_Lock_policy)2>::~__shared_ptr (this=0x190bb80, __in_chrg=<optimized out>)
    at /usr/include/c++/11/bits/shared_ptr_base.h:1154
 #12 0x000000000082ff0a in std::shared_ptr<objfile>::~shared_ptr (
    this=0x190bb80, __in_chrg=<optimized out>)
    at /usr/include/c++/11/bits/shared_ptr.h:122
 #13 0x000000000085ed7e in __gnu_cxx::new_allocator<std::_List_node<std::shared_ptr<objfile> > >::destroy<std::shared_ptr<objfile> > (this=0x114bc00,
    __p=0x190bb80) at /usr/include/c++/11/ext/new_allocator.h:168
 #14 0x000000000085e88d in std::allocator_traits<std::allocator<std::_List_node<std::shared_ptr<objfile> > > >::destroy<std::shared_ptr<objfile> > (__a=...,
    __p=0x190bb80) at /usr/include/c++/11/bits/alloc_traits.h:531
 #15 0x000000000085e50c in std::__cxx11::list<std::shared_ptr<objfile>, std::allocator<std::shared_ptr<objfile> > >::_M_erase (this=0x114bc00, __position=
  std::shared_ptr<objfile> (expired, weak count 1) = {get() = 0x1635930})
    at /usr/include/c++/11/bits/stl_list.h:1925
 #16 0x000000000085df0e in std::__cxx11::list<std::shared_ptr<objfile>, std::allocator<std::shared_ptr<objfile> > >::erase (this=0x114bc00, __position=
  std::shared_ptr<objfile> (expired, weak count 1) = {get() = 0x1635930})
    at /usr/include/c++/11/bits/list.tcc:158
 #17 0x000000000085c748 in program_space::remove_objfile (this=0x114bbc0,
    objfile=0x1635930)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/progspace.c:210
 #18 0x000000000082d3ae in objfile::unlink (this=0x1635930)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/objfiles.c:487
 #19 0x000000000082e68c in objfile_purge_solibs ()
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/objfiles.c:875
 #20 0x000000000092dd37 in no_shared_libraries (ignored=0x0, from_tty=1)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/solib.c:1236
 #21 0x00000000009a37fe in target_pre_inferior (from_tty=1)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/target.c:2496
 #22 0x00000000007454d6 in run_command_1 (args=0x0, from_tty=1,
    run_how=RUN_NORMAL)
    at /ironwood1/sourceware-git/f34-pr28030/bld/../../worktree-pr28030/gdb/infcmd.c:437

I'll note a few points regarding this backtrace:

Frame #1 is where the internal error occurs.  It's caused by an
unhandled case for FIELD_LOC_KIND_DWARF_BLOCK.  The fix for this bug
adds support for this case.

Frame #22 - it's a partial backtrace - shows that GDB is attempting to
(re)run the program.  You can see the exact command sequence that was
used for reproducing this problem in the PR (at
https://sourceware.org/bugzilla/show_bug.cgi?id=28030), but in a
nutshell, after starting the program and advancing to the appropriate
source line, GDB was asked to step into libstdc++; a "finish" command
was issued, returning a value.  The fact that a value was returned is
very important.  GDB was then used to step back into libstdc++.  A
breakpoint was set on a source line in the library after which a "run"
command was issued.

Frame #19 shows a call to objfile_purge_solibs.  It's aptly named.

Frame #7 is a call to the destructor for one of the objfile solibs; it
turned out to be the one for libstdc++.

Frames #6 thru #3 show various value preservation frames.  If you look
at preserve_values() in gdb/value.c, the value history is preserved
first, followed by internal variables, followed by values for the
extension languages (python and guile).
2021-09-03 08:54:12 -07:00
bfd ubsan: alpha: member access within null pointer 2021-09-03 11:45:58 +09:30
binutils CC_FOR_TARGET et al 2021-09-03 16:26:09 +09:30
config Deprecate a.out support for NetBSD targets. 2021-08-11 13:17:54 +01:00
contrib
cpu Re: opcodes: constify & local meps macros 2021-07-05 21:40:49 +09:30
elfcpp PATCH [4/4] arm: Add Tag_PACRET_use build attribute 2021-08-17 14:49:42 +02:00
etc texi2pod.pl: add no-op --no-split option support [PR28144] 2021-07-28 11:39:40 +01:00
gas Add support for the haiku operating system. These are the os support patches we have been grooming and maintaining for quite a few years over on git.haiku-os.org. All of these architectures are working and most have been stable for quite some time. 2021-09-02 12:19:14 +01:00
gdb Test case reproducing PR28030 bug 2021-09-03 08:54:12 -07:00
gdbserver gdbserver: Check r_version < 1 for Linux debugger interface 2021-08-17 06:19:49 -07:00
gdbsupport gdbsupport: add debug assertions in gdb::optional::get 2021-08-03 08:50:56 -04:00
gnulib gnulib: define the path to gnulib's parent dir 2021-06-14 18:01:20 -04:00
gold gold: --export-dynamic-symbol: don't imply -u 2021-09-02 19:07:53 -07:00
gprof Add support for the haiku operating system. These are the os support patches we have been grooming and maintaining for quite a few years over on git.haiku-os.org. All of these architectures are working and most have been stable for quite some time. 2021-09-02 12:19:14 +01:00
include obstack.h __PTR_ALIGN vs. ubsan 2021-09-02 13:48:21 +09:30
intl Deprecate a.out support for NetBSD targets. 2021-08-11 13:17:54 +01:00
ld ld testsuite tidy 2021-09-03 16:26:21 +09:30
libctf CC_FOR_TARGET et al 2021-09-03 16:26:09 +09:30
libdecnumber
libiberty Deprecate a.out support for NetBSD targets. 2021-08-11 13:17:54 +01:00
opcodes pj: asan: out of bounds, ubsan: left shift of negative 2021-09-03 11:45:58 +09:30
readline Update config.sub and config.guess for MIPS R3 and R5 ISA support 2021-05-24 18:11:49 +02:00
sim sim: m32r: add __linux__ hack for non-Linux hosts 2021-08-22 03:11:16 -04:00
texinfo
zlib haiku tidy 2021-09-03 11:45:58 +09:30
.cvsignore
.gitattributes
.gitignore Add gnu global outputs to .gitignore 2020-12-02 10:00:27 -05:00
ar-lib
ChangeLog Add markers for 2.37 branch 2021-07-03 14:50:57 +01:00
compile
config-ml.in
config.guess Update config.sub and config.guess for MIPS R3 and R5 ISA support 2021-05-24 18:11:49 +02:00
config.rpath
config.sub Update config.sub and config.guess for MIPS R3 and R5 ISA support 2021-05-24 18:11:49 +02:00
configure Add support for the haiku operating system. These are the os support patches we have been grooming and maintaining for quite a few years over on git.haiku-os.org. All of these architectures are working and most have been stable for quite some time. 2021-09-02 12:19:14 +01:00
configure.ac Add support for the haiku operating system. These are the os support patches we have been grooming and maintaining for quite a few years over on git.haiku-os.org. All of these architectures are working and most have been stable for quite some time. 2021-09-02 12:19:14 +01:00
COPYING
COPYING3
COPYING3.LIB
COPYING.LIB
COPYING.LIBGLOSS
COPYING.NEWLIB
depcomp
djunpack.bat
install-sh
libtool.m4 Add support for the haiku operating system. These are the os support patches we have been grooming and maintaining for quite a few years over on git.haiku-os.org. All of these architectures are working and most have been stable for quite some time. 2021-09-02 12:19:14 +01:00
lt~obsolete.m4
ltgcc.m4
ltmain.sh
ltoptions.m4
ltsugar.m4
ltversion.m4
MAINTAINERS MAINTAINERS: Update path to readline config.{sub,guess} files 2021-05-24 18:11:49 +02:00
Makefile.def sim: depend on gnulib 2021-05-18 17:47:27 -04:00
Makefile.in sim: depend on gnulib 2021-05-18 17:47:27 -04:00
Makefile.tpl Add missing changes to Makefile.tpl 2021-02-28 04:39:38 -08:00
makefile.vms
missing
mkdep
mkinstalldirs
move-if-change
multilib.am
README
README-maintainer-mode
setup.com
src-release.sh src-release: fix indentation 2021-01-12 18:19:20 -05:00
symlink-tree
test-driver
ylwrap

		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
debuggers, etc., plus their support routines, definitions, and documentation.

If you are receiving this as part of a GDB release, see the file gdb/README.
If with a binutils release, see binutils/README;  if with a libg++ release,
see libg++/README, etc.  That'll give you info about this
package -- supported targets, how to use it, how to report bugs, etc.

It is now possible to automatically configure and build a variety of
tools with one command.  To build all of the tools contained herein,
run the ``configure'' script here, e.g.:

	./configure 
	make

To install them (by default in /usr/local/bin, /usr/local/lib, etc),
then do:
	make install

(If the configure script can't determine your type of computer, give it
the name as an argument, for instance ``./configure sun4''.  You can
use the script ``config.sub'' to test whether a name is recognized; if
it is, config.sub translates it to a triplet specifying CPU, vendor,
and OS.)

If you have more than one compiler on your system, it is often best to
explicitly set CC in the environment before running configure, and to
also set CC when running make.  For example (assuming sh/bash/ksh):

	CC=gcc ./configure
	make

A similar example using csh:

	setenv CC gcc
	./configure
	make

Much of the code and documentation enclosed is copyright by
the Free Software Foundation, Inc.  See the file COPYING or
COPYING.LIB in the various directories, for a description of the
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REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info
on where and how to report problems.