Re: [PATCH 4/6] gdb/progspace: Add reverse safe iterator and template for unwrapping iterator

[Aaron Merey <amerey@redhat.com>]

Ping

Thanks,
Aaron

On Wed, May 31, 2023 at 9:44 PM Aaron Merey <amerey@redhat.com> wrote:
>
> To facilitate the deletion of objfiles, progspace objects use a safe
> iterator that holds a reference to the next objfile in the progspace's
> objfile_list.  This allows objfiles to be deleted in a loop without
> invalidating the loop's iterator.  progspace also uses an unwrapping
> iterator over std::unique_ptr<objfile> that automatically deferences
> the unique_ptr.
>
> This patch changes the objfile safe iterator to be a reverse safe
> iterator.  It changes the unwrapping iterator into a template.  It
> also modifies objfile_list insertion so that separate debug objfiles
> are placed into the list after the parent objfile, instead of before.
>
> These changes are intended to prepare gdb for on-demand debuginfo
> downloading and the downloading of .gdb_index sections.
>
> With on-demand downloading enabled, gdb might download a debuginfo
> file during symtab expansion.  In this case an objfile could be added
> to an objfiles_list during iteration over the list (for example, in
> iterate_over_symtabs).  We want these loops to also iterate over newly
> downloaded objfiles. So objfiles need to be inserted into objfiles_list
> after their parent since it is during the search of the parent
> objfile for some symbol or filename that the separate debug objfile
> might be downloaded.
>
> The unwrapping iterator is changed into a template in order to
> use it with objfile qf_require_partial_symbols, which is now also
> uses with a safe iterator.  This is because after a separate debug
> objfile is downloaded on-demand, we want to remove any .gdb_index
> quick_symbol_functions from the parent objfile during iteration over
> the parent's quick_symbol_functions.  The newly downloaded separate
> debug objfile contains the index and all of the related symbols
> so the .gdb_index should not be associated with the parent objfile
> any longer.
>
> Finally a safe reverse iterator is now used during progspace objfile
> deletion in order to prevent iterator invalidation during the loop
> in which objfiles are deleted.  This could happen during forward
> iteration over objfiles_list when a separate debug objfile immediately
> follows it's parent objfile in the list (which is now possible since
> objfiles are inserted into the list after their parent).  Deletion
> of the parent would cause deletion of the separate debug objfile,
> which would invalidate the safe forward iterator's reference to the
> next objfile in the list.  A safe reverse iterator deletes separate
> debug objfiles before their parent, so the iterator's reference to
> the next objfile always stays valid.
>
> A small change was also made to a testcase in py-objfile.exp to
> account for the new placement of separate debug objfiles in
> objfiles_list.
> ---
>  gdb/objfiles.h                          |  22 +++-
>  gdb/progspace.c                         |   8 +-
>  gdb/progspace.h                         | 159 +++++++++++++++++++-----
>  gdb/symfile-debug.c                     | 136 ++++++++++----------
>  gdb/testsuite/gdb.python/py-objfile.exp |   2 +-
>  5 files changed, 218 insertions(+), 109 deletions(-)
>
> diff --git a/gdb/objfiles.h b/gdb/objfiles.h
> index 189856f0a51..bb7b0a4579d 100644
> --- a/gdb/objfiles.h
> +++ b/gdb/objfiles.h
> @@ -613,6 +613,17 @@ struct objfile
>    /* See quick_symbol_functions.  */
>    void require_partial_symbols (bool verbose);
>
> +  /* Remove TARGET from this objfile's collection of quick_symbol_functions.  */
> +  void remove_partial_symbol (quick_symbol_functions *target)
> +  {
> +    for (quick_symbol_functions_up &qf_up : qf)
> +      if (qf_up.get () == target)
> +       {
> +         qf.remove (qf_up);
> +         return;
> +       }
> +  }
> +
>    /* Return the relocation offset applied to SECTION.  */
>    CORE_ADDR section_offset (bfd_section *section) const
>    {
> @@ -699,13 +710,20 @@ struct objfile
>
>  private:
>
> +  using qf_list = std::forward_list<quick_symbol_functions_up>;
> +  using unwrapping_qf_range = iterator_range<unwrapping_iterator<qf_list::iterator>>;
> +  using qf_safe_range = basic_safe_range<unwrapping_qf_range>;
> +
>    /* Ensure that partial symbols have been read and return the "quick" (aka
>       partial) symbol functions for this symbol reader.  */
> -  const std::forward_list<quick_symbol_functions_up> &
> +  qf_safe_range
>    qf_require_partial_symbols ()
>    {
>      this->require_partial_symbols (true);
> -    return qf;
> +    return qf_safe_range
> +      (unwrapping_qf_range
> +       (unwrapping_iterator<qf_list::iterator> (qf.begin ()),
> +        unwrapping_iterator<qf_list::iterator> (qf.end ())));
>    }
>
>  public:
> diff --git a/gdb/progspace.c b/gdb/progspace.c
> index 32bdfebcf7c..1ed75eef2f9 100644
> --- a/gdb/progspace.c
> +++ b/gdb/progspace.c
> @@ -139,19 +139,19 @@ program_space::free_all_objfiles ()
>
>  void
>  program_space::add_objfile (std::unique_ptr<objfile> &&objfile,
> -                           struct objfile *before)
> +                           struct objfile *after)
>  {
> -  if (before == nullptr)
> +  if (after == nullptr)
>      objfiles_list.push_back (std::move (objfile));
>    else
>      {
>        auto iter = std::find_if (objfiles_list.begin (), objfiles_list.end (),
>                                 [=] (const std::unique_ptr<::objfile> &objf)
>                                 {
> -                                 return objf.get () == before;
> +                                 return objf.get () == after;
>                                 });
>        gdb_assert (iter != objfiles_list.end ());
> -      objfiles_list.insert (iter, std::move (objfile));
> +      objfiles_list.insert (++iter, std::move (objfile));
>      }
>  }
>
> diff --git a/gdb/progspace.h b/gdb/progspace.h
> index 85215f0e2f1..6e33e48c88e 100644
> --- a/gdb/progspace.h
> +++ b/gdb/progspace.h
> @@ -40,56 +40,141 @@ struct address_space;
>  struct program_space;
>  struct so_list;
>
> +/* An iterator that wraps an iterator over std::unique_ptr, and dereferences
> +   the returned object.  This is useful for iterating over a list of shared
> +   pointers and returning raw pointers -- which helped avoid touching a lot
> +   of code when changing how objfiles are managed.  */
> +
> +template<typename UniquePtrIter>
> +class unwrapping_iterator
> +{
> +public:
> +  typedef unwrapping_iterator self_type;
> +  typedef typename UniquePtrIter::value_type::pointer value_type;
> +  typedef typename UniquePtrIter::reference  reference;
> +  typedef typename UniquePtrIter::pointer pointer;
> +  typedef typename UniquePtrIter::iterator_category iterator_category;
> +  typedef typename UniquePtrIter::difference_type difference_type;
> +
> +  unwrapping_iterator (UniquePtrIter iter)
> +    : m_iter (std::move (iter))
> +  {
> +  }
> +
> +  value_type operator* () const
> +  {
> +    return m_iter->get ();
> +  }
> +
> +  unwrapping_iterator operator++ ()
> +  {
> +    ++m_iter;
> +    return *this;
> +  }
> +
> +  bool operator!= (const unwrapping_iterator &other) const
> +  {
> +    return m_iter != other.m_iter;
> +  }
> +
> +private:
> +  /* The underlying iterator.  */
> +  UniquePtrIter m_iter;
> +};
> +
>  typedef std::list<std::unique_ptr<objfile>> objfile_list;
>
> -/* An iterator that wraps an iterator over std::unique_ptr<objfile>,
> -   and dereferences the returned object.  This is useful for iterating
> -   over a list of shared pointers and returning raw pointers -- which
> -   helped avoid touching a lot of code when changing how objfiles are
> -   managed.  */
> +/* An reverse iterator that wraps an iterator over objfile_list, and
> +   dereferences the returned object.  This is useful for reverse iterating
> +   over a list of shared pointers and returning raw pointers -- which helped
> +   avoid touching a lot of code when changing how objfiles are managed.  */
>
> -class unwrapping_objfile_iterator
> +class unwrapping_reverse_objfile_iterator
>  {
>  public:
> -
> -  typedef unwrapping_objfile_iterator self_type;
> +  typedef unwrapping_reverse_objfile_iterator self_type;
>    typedef typename ::objfile *value_type;
>    typedef typename ::objfile &reference;
>    typedef typename ::objfile **pointer;
>    typedef typename objfile_list::iterator::iterator_category iterator_category;
>    typedef typename objfile_list::iterator::difference_type difference_type;
>
> -  unwrapping_objfile_iterator (objfile_list::iterator iter)
> -    : m_iter (std::move (iter))
> -  {
> -  }
> -
> -  objfile *operator* () const
> +  value_type operator* () const
>    {
>      return m_iter->get ();
>    }
>
> -  unwrapping_objfile_iterator operator++ ()
> +  unwrapping_reverse_objfile_iterator operator++ ()
>    {
> -    ++m_iter;
> +    if (m_iter != m_begin)
> +      --m_iter;
> +    else
> +      {
> +       /* We can't decrement M_ITER since it is the begin iterator of the
> +          objfile list.  Set M_ITER to the list's end iterator to indicate
> +          this is now one-past-the-end.  */
> +       m_iter = m_end;
> +
> +       /* Overwrite M_BEGIN to avoid possibly copying an invalid iterator.  */
> +       m_begin = m_end;
> +      }
> +
>      return *this;
>    }
>
> -  bool operator!= (const unwrapping_objfile_iterator &other) const
> +  bool operator!= (const unwrapping_reverse_objfile_iterator &other) const
>    {
>      return m_iter != other.m_iter;
>    }
>
> +  /* Return an unwrapping reverse iterator starting at the last element of
> +     OBJF_LIST.  */
> +  static unwrapping_reverse_objfile_iterator begin (objfile_list &objf_list)
> +  {
> +    auto begin = objf_list.begin ();
> +    auto end = objf_list.end ();
> +    auto rev_begin = objf_list.end ();
> +
> +    /* Start REV_BEGIN on the last objfile in OBJF_LIST.  */
> +    if (begin != end)
> +      --rev_begin;
> +
> +    return unwrapping_reverse_objfile_iterator (rev_begin, begin, end);
> +  }
> +
> +  /* Return a one-past-the-end unwrapping reverse iterator.  */
> +  static unwrapping_reverse_objfile_iterator end (objfile_list &objf_list)
> +  {
> +    return unwrapping_reverse_objfile_iterator (objf_list.end (),
> +                                               objf_list.end (),
> +                                               objf_list.end ());
> +  }
> +
>  private:
> +  /* begin and end methods should be used to create these objects.  */
> +  unwrapping_reverse_objfile_iterator (objfile_list::iterator iter,
> +                                      objfile_list::iterator begin,
> +                                      objfile_list::iterator end)
> +    : m_iter (std::move (iter)), m_begin (std::move (begin)),
> +      m_end (std::move (end))
> +  {
> +  }
>
> -  /* The underlying iterator.  */
> -  objfile_list::iterator m_iter;
> -};
> + /* The underlying iterator.  */
> + objfile_list::iterator m_iter;
>
> + /* The underlying iterator pointing to the first objfile in the sequence.  Used
> +    to track when to stop decrementing M_ITER.  */
> + objfile_list::iterator m_begin;
>
> -/* A range that returns unwrapping_objfile_iterators.  */
> +  /* The underlying iterator's one-past-the-end.  */
> + objfile_list::iterator m_end;
> +};
>
> -using unwrapping_objfile_range = iterator_range<unwrapping_objfile_iterator>;
> +/* A range that returns unwrapping_iterators.  */
> +
> +using unwrapping_objfile_range
> +  = iterator_range<unwrapping_iterator<objfile_list::iterator>>;
>
>  /* A program space represents a symbolic view of an address space.
>     Roughly speaking, it holds all the data associated with a
> @@ -209,11 +294,12 @@ struct program_space
>    objfiles_range objfiles ()
>    {
>      return objfiles_range
> -      (unwrapping_objfile_iterator (objfiles_list.begin ()),
> -       unwrapping_objfile_iterator (objfiles_list.end ()));
> +      (unwrapping_iterator<objfile_list::iterator> (objfiles_list.begin ()),
> +       unwrapping_iterator<objfile_list::iterator> (objfiles_list.end ()));
>    }
>
> -  using objfiles_safe_range = basic_safe_range<objfiles_range>;
> +  using objfiles_reverse_range = iterator_range<unwrapping_reverse_objfile_iterator>;
> +  using objfiles_safe_reverse_range = basic_safe_range<objfiles_reverse_range>;
>
>    /* An iterable object that can be used to iterate over all objfiles.
>       The basic use is in a foreach, like:
> @@ -221,20 +307,25 @@ struct program_space
>       for (objfile *objf : pspace->objfiles_safe ()) { ... }
>
>       This variant uses a basic_safe_iterator so that objfiles can be
> -     deleted during iteration.  */
> -  objfiles_safe_range objfiles_safe ()
> +     deleted during iteration.
> +
> +     The use of a reverse iterator helps ensure that separate debug
> +     objfiles are deleted before their parent objfile.  This prevents
> +     the invalidation of an iterator due to the deletion of a parent
> +     objfile.  */
> +  objfiles_safe_reverse_range objfiles_safe ()
>    {
> -    return objfiles_safe_range
> -      (objfiles_range
> -        (unwrapping_objfile_iterator (objfiles_list.begin ()),
> -         unwrapping_objfile_iterator (objfiles_list.end ())));
> +    return objfiles_safe_reverse_range
> +      (objfiles_reverse_range
> +       (unwrapping_reverse_objfile_iterator::begin (objfiles_list),
> +        unwrapping_reverse_objfile_iterator::end (objfiles_list)));
>    }
>
> -  /* Add OBJFILE to the list of objfiles, putting it just before
> -     BEFORE.  If BEFORE is nullptr, it will go at the end of the
> +  /* Add OBJFILE to the list of objfiles, putting it just after
> +     AFTER.  If AFTER is nullptr, it will go at the end of the
>       list.  */
>    void add_objfile (std::unique_ptr<objfile> &&objfile,
> -                   struct objfile *before);
> +                   struct objfile *after);
>
>    /* Remove OBJFILE from the list of objfiles.  */
>    void remove_objfile (struct objfile *objfile);
> diff --git a/gdb/symfile-debug.c b/gdb/symfile-debug.c
> index 9db5c47a8ce..784b81b5ca6 100644
> --- a/gdb/symfile-debug.c
> +++ b/gdb/symfile-debug.c
> @@ -109,9 +109,9 @@ objfile::has_unexpanded_symtabs ()
>                 objfile_debug_name (this));
>
>    bool result = false;
> -  for (const auto &iter : qf_require_partial_symbols ())
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
>      {
> -      if (iter->has_unexpanded_symtabs (this))
> +      if (qf->has_unexpanded_symtabs (this))
>         {
>           result = true;
>           break;
> @@ -134,9 +134,9 @@ objfile::find_last_source_symtab ()
>      gdb_printf (gdb_stdlog, "qf->find_last_source_symtab (%s)\n",
>                 objfile_debug_name (this));
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
>      {
> -      retval = iter->find_last_source_symtab (this);
> +      retval = qf->find_last_source_symtab (this);
>        if (retval != nullptr)
>         break;
>      }
> @@ -167,8 +167,8 @@ objfile::forget_cached_source_info ()
>         }
>      }
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> -    iter->forget_cached_source_info (this);
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
> +    qf->forget_cached_source_info (this);
>  }
>
>  bool
> @@ -214,17 +214,17 @@ objfile::map_symtabs_matching_filename
>      return result;
>    };
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
>      {
> -      if (!iter->expand_symtabs_matching (this,
> -                                         match_one_filename,
> -                                         nullptr,
> -                                         nullptr,
> -                                         on_expansion,
> -                                         (SEARCH_GLOBAL_BLOCK
> -                                          | SEARCH_STATIC_BLOCK),
> -                                         UNDEF_DOMAIN,
> -                                         ALL_DOMAIN))
> +      if (!qf->expand_symtabs_matching (this,
> +                                       match_one_filename,
> +                                       nullptr,
> +                                       nullptr,
> +                                       on_expansion,
> +                                       (SEARCH_GLOBAL_BLOCK
> +                                        | SEARCH_STATIC_BLOCK),
> +                                       UNDEF_DOMAIN,
> +                                       ALL_DOMAIN))
>         {
>           retval = false;
>           break;
> @@ -283,18 +283,18 @@ objfile::lookup_symbol (block_enum kind, const char *name, domain_enum domain)
>      return true;
>    };
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
>      {
> -      if (!iter->expand_symtabs_matching (this,
> -                                         nullptr,
> -                                         &lookup_name,
> -                                         nullptr,
> -                                         search_one_symtab,
> -                                         kind == GLOBAL_BLOCK
> -                                         ? SEARCH_GLOBAL_BLOCK
> -                                         : SEARCH_STATIC_BLOCK,
> -                                         domain,
> -                                         ALL_DOMAIN))
> +      if (!qf->expand_symtabs_matching (this,
> +                                       nullptr,
> +                                       &lookup_name,
> +                                       nullptr,
> +                                       search_one_symtab,
> +                                       kind == GLOBAL_BLOCK
> +                                       ? SEARCH_GLOBAL_BLOCK
> +                                       : SEARCH_STATIC_BLOCK,
> +                                       domain,
> +                                       ALL_DOMAIN))
>         break;
>      }
>
> @@ -314,8 +314,8 @@ objfile::print_stats (bool print_bcache)
>      gdb_printf (gdb_stdlog, "qf->print_stats (%s, %d)\n",
>                 objfile_debug_name (this), print_bcache);
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> -    iter->print_stats (this, print_bcache);
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
> +    qf->print_stats (this, print_bcache);
>  }
>
>  void
> @@ -340,16 +340,16 @@ objfile::expand_symtabs_for_function (const char *func_name)
>    lookup_name_info base_lookup (func_name, symbol_name_match_type::FULL);
>    lookup_name_info lookup_name = base_lookup.make_ignore_params ();
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> -    iter->expand_symtabs_matching (this,
> -                                  nullptr,
> -                                  &lookup_name,
> -                                  nullptr,
> -                                  nullptr,
> -                                  (SEARCH_GLOBAL_BLOCK
> -                                   | SEARCH_STATIC_BLOCK),
> -                                  VAR_DOMAIN,
> -                                  ALL_DOMAIN);
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
> +    qf->expand_symtabs_matching (this,
> +                                nullptr,
> +                                &lookup_name,
> +                                nullptr,
> +                                nullptr,
> +                                (SEARCH_GLOBAL_BLOCK
> +                                 | SEARCH_STATIC_BLOCK),
> +                                VAR_DOMAIN,
> +                                ALL_DOMAIN);
>  }
>
>  void
> @@ -359,8 +359,8 @@ objfile::expand_all_symtabs ()
>      gdb_printf (gdb_stdlog, "qf->expand_all_symtabs (%s)\n",
>                 objfile_debug_name (this));
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> -    iter->expand_all_symtabs (this);
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
> +    qf->expand_all_symtabs (this);
>  }
>
>  void
> @@ -377,16 +377,16 @@ objfile::expand_symtabs_with_fullname (const char *fullname)
>      return filename_cmp (basenames ? basename : fullname, filename) == 0;
>    };
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> -    iter->expand_symtabs_matching (this,
> -                                  file_matcher,
> -                                  nullptr,
> -                                  nullptr,
> -                                  nullptr,
> -                                  (SEARCH_GLOBAL_BLOCK
> -                                   | SEARCH_STATIC_BLOCK),
> -                                  UNDEF_DOMAIN,
> -                                  ALL_DOMAIN);
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
> +    qf->expand_symtabs_matching (this,
> +                                file_matcher,
> +                                nullptr,
> +                                nullptr,
> +                                nullptr,
> +                                (SEARCH_GLOBAL_BLOCK
> +                                 | SEARCH_STATIC_BLOCK),
> +                                UNDEF_DOMAIN,
> +                                ALL_DOMAIN);
>  }
>
>  void
> @@ -402,9 +402,9 @@ objfile::expand_matching_symbols
>                 domain_name (domain), global,
>                 host_address_to_string (ordered_compare));
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> -    iter->expand_matching_symbols (this, name, domain, global,
> -                                  ordered_compare);
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
> +    qf->expand_matching_symbols (this, name, domain, global,
> +                                ordered_compare);
>  }
>
>  bool
> @@ -429,10 +429,10 @@ objfile::expand_symtabs_matching
>                 host_address_to_string (&expansion_notify),
>                 search_domain_name (kind));
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> -    if (!iter->expand_symtabs_matching (this, file_matcher, lookup_name,
> -                                       symbol_matcher, expansion_notify,
> -                                       search_flags, domain, kind))
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
> +    if (!qf->expand_symtabs_matching (this, file_matcher, lookup_name,
> +                                     symbol_matcher, expansion_notify,
> +                                     search_flags, domain, kind))
>        return false;
>    return true;
>  }
> @@ -454,10 +454,10 @@ objfile::find_pc_sect_compunit_symtab (struct bound_minimal_symbol msymbol,
>                 host_address_to_string (section),
>                 warn_if_readin);
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
>      {
> -      retval = iter->find_pc_sect_compunit_symtab (this, msymbol, pc, section,
> -                                                  warn_if_readin);
> +      retval = qf->find_pc_sect_compunit_symtab (this, msymbol, pc, section,
> +                                                warn_if_readin);
>        if (retval != nullptr)
>         break;
>      }
> @@ -482,8 +482,8 @@ objfile::map_symbol_filenames (gdb::function_view<symbol_filename_ftype> fun,
>                 objfile_debug_name (this),
>                 need_fullname);
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> -    iter->map_symbol_filenames (this, fun, need_fullname);
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
> +    qf->map_symbol_filenames (this, fun, need_fullname);
>  }
>
>  struct compunit_symtab *
> @@ -496,9 +496,9 @@ objfile::find_compunit_symtab_by_address (CORE_ADDR address)
>                 hex_string (address));
>
>    struct compunit_symtab *result = NULL;
> -  for (const auto &iter : qf_require_partial_symbols ())
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
>      {
> -      result = iter->find_compunit_symtab_by_address (this, address);
> +      result = qf->find_compunit_symtab_by_address (this, address);
>        if (result != nullptr)
>         break;
>      }
> @@ -521,10 +521,10 @@ objfile::lookup_global_symbol_language (const char *name,
>    enum language result = language_unknown;
>    *symbol_found_p = false;
>
> -  for (const auto &iter : qf_require_partial_symbols ())
> +  for (quick_symbol_functions *qf : qf_require_partial_symbols ())
>      {
> -      result = iter->lookup_global_symbol_language (this, name, domain,
> -                                                   symbol_found_p);
> +      result = qf->lookup_global_symbol_language (this, name, domain,
> +                                                 symbol_found_p);
>        if (*symbol_found_p)
>         break;
>      }
> diff --git a/gdb/testsuite/gdb.python/py-objfile.exp b/gdb/testsuite/gdb.python/py-objfile.exp
> index 61b9942de79..0bf49976b73 100644
> --- a/gdb/testsuite/gdb.python/py-objfile.exp
> +++ b/gdb/testsuite/gdb.python/py-objfile.exp
> @@ -135,7 +135,7 @@ gdb_test "p main" "= {<text variable, no debug info>} $hex <main>" \
>  gdb_py_test_silent_cmd "python objfile.add_separate_debug_file(\"${binfile}\")" \
>      "Add separate debug file file" 1
>
> -gdb_py_test_silent_cmd "python sep_objfile = gdb.objfiles()\[0\]" \
> +gdb_py_test_silent_cmd "python sep_objfile = gdb.objfiles()\[1\]" \
>      "Get separate debug info objfile" 1
>
>  gdb_test "python print (sep_objfile.owner.filename)" "${testfile}2" \
> --
> 2.40.1
>