Share DWARF partial symtabs
This changes the DWARF reader to share partial symtabs (or indices if they are available) across objfiles. This has a few parts. * If multiple objfiles backed by the same BFD can share partial symtabs (see below), a single dwarf2_per_bfd is created. It is stored in the per-bfd `dwarf2_per_bfd_bfd_data_key` registry. Multiple dwarf2_per_objfile objects will point to the same instance. The lifetime of these dwarf2_per_bfd objects is naturally handled. When all the objfiles using the BFD are destroyed, the BFD's refount drops to 0, which triggers the removal of the corresponding dwarf2_per_bfd object from the registry and its destruction. * If multiple objfiles backed by the same BFD can't share partial symtabs (see below), one dwarf2_per_bfd object is created for each objfile. Each dwarf2_per_objfile will point to their own instance of dwarf2_per_bfd. These instances of dwarf2_per_bfd are kept in a per-objfile registry, meaning that when the objfile gets destroyed, the dwarf2_per_bfd instance gets destroyed as well. * objfile::partial_symtabs is changed to be a shared_ptr again. This lets us stash a second reference in dwarf2_per_bfd; if the DWARF data is being shared, we can simply copy this value to the new objfile. * Two dwarf2_per_objfile objects backed by the same BFD may share a dwarf2_per_bfd instance if: * No other symbol reader has found symbols, and * No BFD section rqeuires relocation gdb/ChangeLog: YYYY-MM-DD Tom Tromey <tom@tromey.com> YYYY-MM-DD Simon Marchi <simon.marchi@efficios.com> * objfiles.h (struct objfile) <partial_symtabs>: Now a shared_ptr. * dwarf2/read.h (struct dwarf2_per_objfile) <partial_symtabs>: New member. * dwarf2/read.c (dwarf2_per_bfd_bfd_data_key, dwarf2_per_bfd_objfile_data_key>: New globals. (dwarf2_has_info): Use shared dwarf2_per_bfd if possible. (dwarf2_get_section_info): Use get_dwarf2_per_objfile. (dwarf2_initialize_objfile): Consider cases where per_bfd can be shared. (dwarf2_build_psymtabs): Set objfile::partial_symtabs and short-circuit when sharing. (dwarf2_build_psymtabs): Set dwarf2_per_objfile::partial_symtabs. (dwarf2_psymtab::expand_psymtab): Use free_cached_comp_units. Change-Id: I868c64448589102ab8cbb8f06c31a8de50a14004
This commit is contained in:
Tom Tromey
Simon Marchi
parent
39b16f87f7
commit
17ee85fc2a
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@ -1,3 +1,21 @@
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2020-05-27 Tom Tromey <tom@tromey.com>
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Simon Marchi <simon.marchi@efficios.com>
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* objfiles.h (struct objfile) <partial_symtabs>: Now a
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shared_ptr.
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* dwarf2/read.h (struct dwarf2_per_objfile) <partial_symtabs>: New
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member.
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* dwarf2/read.c (dwarf2_per_bfd_bfd_data_key,
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dwarf2_per_bfd_objfile_data_key>: New globals.
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(dwarf2_has_info): Use shared dwarf2_per_bfd if possible.
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(dwarf2_get_section_info): Use get_dwarf2_per_objfile.
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(dwarf2_initialize_objfile): Consider cases where per_bfd can be
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shared.
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(dwarf2_build_psymtabs): Set objfile::partial_symtabs and
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short-circuit when sharing.
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(dwarf2_build_psymtabs): Set dwarf2_per_objfile::partial_symtabs.
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(dwarf2_psymtab::expand_psymtab): Use free_cached_comp_units.
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2020-05-27 Simon Marchi <simon.marchi@efficios.com>
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* dwarf2/read.h (struct dwarf2_per_bfd) <line_header_hash>: Move
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@ -105,7 +105,19 @@ static bool check_physname = false;
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/* When true, do not reject deprecated .gdb_index sections. */
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static bool use_deprecated_index_sections = false;
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static const struct objfile_key<dwarf2_per_objfile> dwarf2_objfile_data_key;
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/* This is used to store the data that is always per objfile. */
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static const objfile_key<dwarf2_per_objfile> dwarf2_objfile_data_key;
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/* These are used to store the dwarf2_per_bfd objects.
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objfiles having the same BFD, which doesn't require relocations, are going to
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share a dwarf2_per_bfd object, which is held in the _bfd_data_key version.
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Other objfiles are not going to share a dwarf2_per_bfd with any other
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objfiles, so they'll have their own version kept in the _objfile_data_key
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version. */
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static const struct bfd_key<dwarf2_per_bfd> dwarf2_per_bfd_bfd_data_key;
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static const struct objfile_key<dwarf2_per_bfd> dwarf2_per_bfd_objfile_data_key;
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/* The "aclass" indices for various kinds of computed DWARF symbols. */
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@ -1853,9 +1865,30 @@ dwarf2_has_info (struct objfile *objfile,
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if (dwarf2_per_objfile == NULL)
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{
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/* For now, each dwarf2_per_objfile owns its own dwarf2_per_bfd (no
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sharing yet). */
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dwarf2_per_bfd *per_bfd = new dwarf2_per_bfd (objfile->obfd, names, can_copy);
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dwarf2_per_bfd *per_bfd;
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/* We can share a "dwarf2_per_bfd" with other objfiles if the BFD
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doesn't require relocations and if there aren't partial symbols
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from some other reader. */
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if (!objfile_has_partial_symbols (objfile)
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&& !gdb_bfd_requires_relocations (objfile->obfd))
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{
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/* See if one has been created for this BFD yet. */
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per_bfd = dwarf2_per_bfd_bfd_data_key.get (objfile->obfd);
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if (per_bfd == nullptr)
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{
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/* No, create it now. */
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per_bfd = new dwarf2_per_bfd (objfile->obfd, names, can_copy);
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dwarf2_per_bfd_bfd_data_key.set (objfile->obfd, per_bfd);
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}
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}
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else
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{
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/* No sharing possible, create one specifically for this objfile. */
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per_bfd = new dwarf2_per_bfd (objfile->obfd, names, can_copy);
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dwarf2_per_bfd_objfile_data_key.set (objfile, per_bfd);
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}
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dwarf2_per_objfile = dwarf2_objfile_data_key.emplace (objfile, objfile, per_bfd);
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}
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@ -2017,7 +2050,7 @@ dwarf2_get_section_info (struct objfile *objfile,
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asection **sectp, const gdb_byte **bufp,
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bfd_size_type *sizep)
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{
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struct dwarf2_per_objfile *data = dwarf2_objfile_data_key.get (objfile);
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struct dwarf2_per_objfile *data = get_dwarf2_per_objfile (objfile);
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struct dwarf2_section_info *info;
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/* We may see an objfile without any DWARF, in which case we just
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@ -5913,6 +5946,7 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
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{
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struct dwarf2_per_objfile *dwarf2_per_objfile
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= get_dwarf2_per_objfile (objfile);
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dwarf2_per_bfd *per_bfd = dwarf2_per_objfile->per_bfd;
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/* If we're about to read full symbols, don't bother with the
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indices. In this case we also don't care if some other debug
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@ -5920,20 +5954,28 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
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expanded anyway. */
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if ((objfile->flags & OBJF_READNOW))
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{
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dwarf2_per_objfile->per_bfd->using_index = 1;
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/* When using READNOW, the using_index flag (set below) indicates that
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PER_BFD was already initialized, when we loaded some other objfile. */
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if (per_bfd->using_index)
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{
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*index_kind = dw_index_kind::GDB_INDEX;
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dwarf2_per_objfile->resize_symtabs ();
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return true;
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}
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per_bfd->using_index = 1;
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create_all_comp_units (dwarf2_per_objfile);
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create_all_type_units (dwarf2_per_objfile);
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dwarf2_per_objfile->per_bfd->quick_file_names_table
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= create_quick_file_names_table
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(dwarf2_per_objfile->per_bfd->all_comp_units.size ());
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per_bfd->quick_file_names_table
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= create_quick_file_names_table (per_bfd->all_comp_units.size ());
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dwarf2_per_objfile->resize_symtabs ();
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for (int i = 0; i < (dwarf2_per_objfile->per_bfd->all_comp_units.size ()
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+ dwarf2_per_objfile->per_bfd->all_type_units.size ()); ++i)
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for (int i = 0; i < (per_bfd->all_comp_units.size ()
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+ per_bfd->all_type_units.size ()); ++i)
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{
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dwarf2_per_cu_data *per_cu = dwarf2_per_objfile->per_bfd->get_cutu (i);
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dwarf2_per_cu_data *per_cu = per_bfd->get_cutu (i);
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per_cu->v.quick = OBSTACK_ZALLOC (&dwarf2_per_objfile->per_bfd->obstack,
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per_cu->v.quick = OBSTACK_ZALLOC (&per_bfd->obstack,
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struct dwarf2_per_cu_quick_data);
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}
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@ -5944,6 +5986,24 @@ dwarf2_initialize_objfile (struct objfile *objfile, dw_index_kind *index_kind)
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return true;
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}
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/* Was a debug names index already read when we processed an objfile sharing
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PER_BFD? */
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if (per_bfd->debug_names_table != nullptr)
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{
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*index_kind = dw_index_kind::DEBUG_NAMES;
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dwarf2_per_objfile->resize_symtabs ();
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return true;
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}
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/* Was a GDB index already read when we processed an objfile sharing
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PER_BFD? */
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if (per_bfd->index_table != nullptr)
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{
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*index_kind = dw_index_kind::GDB_INDEX;
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dwarf2_per_objfile->resize_symtabs ();
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return true;
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}
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if (dwarf2_read_debug_names (dwarf2_per_objfile))
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{
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*index_kind = dw_index_kind::DEBUG_NAMES;
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@ -5984,6 +6044,16 @@ dwarf2_build_psymtabs (struct objfile *objfile)
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{
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struct dwarf2_per_objfile *dwarf2_per_objfile
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= get_dwarf2_per_objfile (objfile);
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dwarf2_per_bfd *per_bfd = dwarf2_per_objfile->per_bfd;
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if (per_bfd->partial_symtabs != nullptr)
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{
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/* Partial symbols were already read, so now we can simply
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attach them. */
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objfile->partial_symtabs = per_bfd->partial_symtabs;
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dwarf2_per_objfile->resize_symtabs ();
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return;
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}
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init_psymbol_list (objfile, 1024);
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@ -6005,6 +6075,12 @@ dwarf2_build_psymtabs (struct objfile *objfile)
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{
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exception_print (gdb_stderr, except);
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}
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/* Finish by setting the local reference to partial symtabs, so that
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we don't try to read them again if reading another objfile with the same
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BFD. If we can't in fact share, this won't make a difference anyway as
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the dwarf2_per_bfd object won't be shared. */
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per_bfd->partial_symtabs = objfile->partial_symtabs;
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}
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/* Find the base address of the compilation unit for range lists and
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@ -9053,9 +9129,10 @@ dwarf2_psymtab::expand_psymtab (struct objfile *objfile)
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{
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gdb_assert (!readin_p (objfile));
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dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
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free_cached_comp_units freer (per_objfile);
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expand_dependencies (objfile);
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dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
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dw2_do_instantiate_symtab (per_cu_data, per_objfile, false);
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gdb_assert (get_compunit_symtab (objfile) != nullptr);
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}
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@ -251,6 +251,11 @@ public:
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/* CUs that are queued to be read. */
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std::queue<dwarf2_queue_item> queue;
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/* We keep a separate reference to the partial symtabs, in case we
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are sharing them between objfiles. This is only set after
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partial symbols have been read the first time. */
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std::shared_ptr<psymtab_storage> partial_symtabs;
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private:
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/* The total number of per_cu and signatured_type objects that have
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@ -576,7 +576,7 @@ public:
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/* The partial symbol tables. */
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std::unique_ptr<psymtab_storage> partial_symtabs;
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std::shared_ptr<psymtab_storage> partial_symtabs;
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/* The object file's BFD. Can be null if the objfile contains only
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minimal symbols, e.g. the run time common symbols for SunOS4. */
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