binutils-gdb/gdb/dwarf2/cooked-index-shard.c

/* Shards for the cooked index

   Copyright (C) 2022-2025 Free Software Foundation, Inc.

   This file is part of GDB.

   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/>.  */

#include "dwarf2/cooked-index-shard.h"
#include "dwarf2/tag.h"
#include "dwarf2/index-common.h"
#include "cp-support.h"
#include "c-lang.h"
#include "ada-lang.h"

/* Return true if a plain "main" could be the main program for this
   language.  Languages that are known to use some other mechanism are
   excluded here.  */

static bool
language_may_use_plain_main (enum language lang)
{
  /* No need to handle "unknown" here.  */
  return (lang == language_c
	  || lang == language_objc
	  || lang == language_cplus
	  || lang == language_m2
	  || lang == language_asm
	  || lang == language_opencl
	  || lang == language_minimal);
}

/* See cooked-index-shard.h.  */

cooked_index_entry *
cooked_index_shard::create (sect_offset die_offset,
			    enum dwarf_tag tag,
			    cooked_index_flag flags,
			    enum language lang,
			    const char *name,
			    cooked_index_entry_ref parent_entry,
			    dwarf2_per_cu *per_cu)
{
  if (tag == DW_TAG_module || tag == DW_TAG_namespace)
    flags &= ~IS_STATIC;
  else if (lang == language_cplus
	   && (tag == DW_TAG_class_type
	       || tag == DW_TAG_interface_type
	       || tag == DW_TAG_structure_type
	       || tag == DW_TAG_union_type
	       || tag == DW_TAG_enumeration_type
	       || tag == DW_TAG_enumerator))
    flags &= ~IS_STATIC;
  else if (tag_is_type (tag))
    flags |= IS_STATIC;

  return new (&m_storage) cooked_index_entry (die_offset, tag, flags,
					      lang, name, parent_entry,
					      per_cu);
}

/* See cooked-index-shard.h.  */

cooked_index_entry *
cooked_index_shard::add (sect_offset die_offset, enum dwarf_tag tag,
			 cooked_index_flag flags, enum language lang,
			 const char *name, cooked_index_entry_ref parent_entry,
			 dwarf2_per_cu *per_cu)
{
  cooked_index_entry *result = create (die_offset, tag, flags, lang, name,
				       parent_entry, per_cu);
  m_entries.push_back (result);

  /* An explicitly-tagged main program should always override the
     implicit "main" discovery.  */
  if ((flags & IS_MAIN) != 0)
    m_main = result;
  /* The language check here is subtle: it exists solely to work
     around a bug in .gdb_index.  That index does not record
     languages, but it might emit an entry for "main".  However,
     recognizing this "main" as being the main program would be wrong
     -- for example, an Ada program has a C "main" but this is not the
     desired target of the "start" command.  Requiring the language to
     be set here avoids over-eagerly setting the "main" when using
     .gdb_index.  Should .gdb_index ever be removed (PR symtab/31363),
     the language_unknown check here could also be removed.

     Note that this explicit check isn't truly needed (it is covered
     by language_may_use_plain_main as well), but it's handy as a spot
     to document.  */
  else if (lang != language_unknown
	   && (flags & IS_PARENT_DEFERRED) == 0
	   && parent_entry.resolved == nullptr
	   && m_main == nullptr
	   && language_may_use_plain_main (lang)
	   && strcmp (name, "main") == 0)
    m_main = result;

  return result;
}

/* See cooked-index-shard.h.  */

void
cooked_index_shard::handle_gnat_encoded_entry
     (cooked_index_entry *entry,
      htab_t gnat_entries,
      std::vector<cooked_index_entry *> &new_entries)
{
  /* We decode Ada names in a particular way: operators and wide
     characters are left as-is.  This is done to make name matching a
     bit simpler; and for wide characters, it means the choice of Ada
     source charset does not affect the indexer directly.  */
  std::string canonical = ada_decode (entry->name, false, false);
  if (canonical.empty ())
    {
      entry->canonical = entry->name;
      return;
    }
  std::vector<std::string_view> names = split_name (canonical.c_str (),
						    split_style::DOT_STYLE);
  std::string_view tail = names.back ();
  names.pop_back ();

  const cooked_index_entry *parent = nullptr;
  for (const auto &name : names)
    {
      uint32_t hashval = dwarf5_djb_hash (name);
      void **slot = htab_find_slot_with_hash (gnat_entries, &name,
					      hashval, INSERT);
      /* CUs are processed in order, so we only need to check the most
	 recent entry.  */
      cooked_index_entry *last = (cooked_index_entry *) *slot;
      if (last == nullptr || last->per_cu != entry->per_cu)
	{
	  const char *new_name = m_names.insert (name);
	  last = create (entry->die_offset, DW_TAG_module,
			 IS_SYNTHESIZED, language_ada, new_name, parent,
			 entry->per_cu);
	  last->canonical = last->name;
	  new_entries.push_back (last);
	  *slot = last;
	}

      parent = last;
    }

  entry->set_parent (parent);
  entry->canonical = m_names.insert (tail);
}

/* Hash a cooked index entry by name pointer value.

   We can use pointer equality here because names come from .debug_str, which
   will normally be unique-ified by the linker.  Also, duplicates are relatively
   harmless -- they just mean a bit of extra memory is used.  */

struct cooked_index_entry_name_ptr_hash
{
  using is_avalanching = void;

  std::uint64_t operator () (const cooked_index_entry *entry) const noexcept
  {
    return ankerl::unordered_dense::hash<const char *> () (entry->name);
  }
};

/* Compare cooked index entries by name pointer value.  */

struct cooked_index_entry_name_ptr_eq
{
  bool operator () (const cooked_index_entry *a,
		    const cooked_index_entry *b) const noexcept
  {
    return a->name == b->name;
  }
};

/* See cooked-index-shard.h.  */

void
cooked_index_shard::finalize (const parent_map_map *parent_maps)
{
  gdb::unordered_set<const cooked_index_entry *,
		     cooked_index_entry_name_ptr_hash,
		     cooked_index_entry_name_ptr_eq> seen_names;

  auto hash_entry = [] (const void *e)
    {
      const cooked_index_entry *entry = (const cooked_index_entry *) e;
      return dwarf5_djb_hash (entry->canonical);
    };

  auto eq_entry = [] (const void *a, const void *b) -> int
    {
      const cooked_index_entry *ae = (const cooked_index_entry *) a;
      const std::string_view *sv = (const std::string_view *) b;
      return (strlen (ae->canonical) == sv->length ()
	      && strncasecmp (ae->canonical, sv->data (), sv->length ()) == 0);
    };

  htab_up gnat_entries (htab_create_alloc (10, hash_entry, eq_entry,
					   nullptr, xcalloc, xfree));
  std::vector<cooked_index_entry *> new_gnat_entries;

  for (cooked_index_entry *entry : m_entries)
    {
      if ((entry->flags & IS_PARENT_DEFERRED) != 0)
	{
	  const cooked_index_entry *new_parent
	    = parent_maps->find (entry->get_deferred_parent ());
	  entry->resolve_parent (new_parent);
	}

      /* Note that this code must be kept in sync with
	 language_requires_canonicalization.  */
      gdb_assert (entry->canonical == nullptr);
      if ((entry->flags & IS_LINKAGE) != 0)
	entry->canonical = entry->name;
      else if (entry->lang == language_ada)
	{
	  /* Newer versions of GNAT emit DW_TAG_module and use a
	     hierarchical structure.  In this case, we don't need to
	     do any extra work.  This can be detected by looking for a
	     GNAT-encoded name.  */
	  if (strstr (entry->name, "__") == nullptr)
	    {
	      entry->canonical = entry->name;

	      /* If the entry does not have a parent, then there's
		 nothing extra to do here -- the entry itself is
		 sufficient.

		 However, if it does have a parent, we have to
		 synthesize an entry with the full name.  This is
		 unfortunate, but it's necessary due to how some of
		 the Ada name-lookup code currently works.  For
		 example, without this, ada_get_tsd_type will
		 fail.

		 Eventually it would be good to change the Ada lookup
		 code, and then remove these entries (and supporting
		 code in cooked_index_entry::full_name).  */
	      if (entry->get_parent () != nullptr)
		{
		  const char *fullname
		    = entry->full_name (&m_storage, FOR_ADA_LINKAGE_NAME);
		  cooked_index_entry *linkage = create (entry->die_offset,
							entry->tag,
							(entry->flags
							 | IS_LINKAGE
							 | IS_SYNTHESIZED),
							language_ada,
							fullname,
							nullptr,
							entry->per_cu);
		  linkage->canonical = fullname;
		  new_gnat_entries.push_back (linkage);
		}
	    }
	  else
	    handle_gnat_encoded_entry (entry, gnat_entries.get (),
				       new_gnat_entries);
	}
      else if (entry->lang == language_cplus || entry->lang == language_c)
	{
	  auto [it, inserted] = seen_names.insert (entry);

	  if (inserted)
	    {
	      /* No entry with that name was present, compute the canonical
		 name.  */
	      gdb::unique_xmalloc_ptr<char> canon_name
		= (entry->lang == language_cplus
		   ? cp_canonicalize_string (entry->name)
		   : c_canonicalize_name (entry->name));
	      if (canon_name == nullptr)
		entry->canonical = entry->name;
	      else
		entry->canonical = m_names.insert (std::move (canon_name));
	    }
	  else
	    {
	      /* An entry with that name was present, re-use its canonical
		 name.  */
	      entry->canonical = (*it)->canonical;
	    }
	}
      else
	entry->canonical = entry->name;
    }

  /* Make sure any new Ada entries end up in the results.  This isn't
     done when creating these new entries to avoid invalidating the
     m_entries iterator used in the foreach above.  */
  m_entries.insert (m_entries.end (), new_gnat_entries.begin (),
		    new_gnat_entries.end ());

  m_entries.shrink_to_fit ();
  std::sort (m_entries.begin (), m_entries.end (),
	     [] (const cooked_index_entry *a, const cooked_index_entry *b)
	     {
	       return *a < *b;
	     });
}

/* See cooked-index-shard.h.  */

cooked_index_shard::range
cooked_index_shard::find (const std::string &name, bool completing) const
{
  struct comparator
  {
    cooked_index_entry::comparison_mode mode;

    bool operator() (const cooked_index_entry *entry,
		     const char *name) const noexcept
    {
      return cooked_index_entry::compare (entry->canonical, name, mode) < 0;
    }

    bool operator() (const char *name,
		     const cooked_index_entry *entry) const noexcept
    {
      return cooked_index_entry::compare (entry->canonical, name, mode) > 0;
    }
  };

  return std::make_from_tuple<range>
    (std::equal_range (m_entries.cbegin (), m_entries.cend (), name.c_str (),
		       comparator { (completing
				     ? cooked_index_entry::COMPLETE
				     : cooked_index_entry::MATCH) }));
}