gdb/dwarf2/cooked-index.c

/* DIE indexing 

   Copyright (C) 2022-2023 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 "defs.h"
#include "dwarf2/cooked-index.h"
#include "dwarf2/read.h"
#include "dwarf2/stringify.h"
#include "dwarf2/index-cache.h"
#include "cp-support.h"
#include "c-lang.h"
#include "ada-lang.h"
#include "split-name.h"
#include "observable.h"
#include "run-on-main-thread.h"
#include <algorithm>
#include "gdbsupport/gdb-safe-ctype.h"
#include "gdbsupport/selftest.h"
#include <chrono>
#include <unordered_set>
#include "cli/cli-cmds.h"

/* We don't want gdb to exit while it is in the process of writing to
   the index cache.  So, all live cooked index vectors are stored
   here, and then these are all waited for before exit proceeds.  */
static std::unordered_set<cooked_index *> active_vectors;

/* See cooked-index.h.  */

std::string
to_string (cooked_index_flag flags)
{
  static constexpr cooked_index_flag::string_mapping mapping[] = {
    MAP_ENUM_FLAG (IS_MAIN),
    MAP_ENUM_FLAG (IS_STATIC),
    MAP_ENUM_FLAG (IS_ENUM_CLASS),
    MAP_ENUM_FLAG (IS_LINKAGE),
    MAP_ENUM_FLAG (IS_TYPE_DECLARATION),
  };

  return flags.to_string (mapping);
}

/* See cooked-index.h.  */

bool
language_requires_canonicalization (enum language lang)
{
  return (lang == language_ada
	  || lang == language_c
	  || lang == language_cplus);
}

/* See cooked-index.h.  */

int
cooked_index_entry::compare (const char *stra, const char *strb,
			     comparison_mode mode)
{
  auto munge = [] (char c) -> unsigned char
    {
      /* We want to sort '<' before any other printable character.
	 So, rewrite '<' to something just before ' '.  */
      if (c == '<')
	return '\x1f';
      return TOLOWER ((unsigned char) c);
    };

  while (*stra != '\0'
	 && *strb != '\0'
	 && (munge (*stra) == munge (*strb)))
    {
      ++stra;
      ++strb;
    }

  unsigned char c1 = munge (*stra);
  unsigned char c2 = munge (*strb);

  if (c1 == c2)
    return 0;

  /* When completing, if STRB ends earlier than STRA, consider them as
     equal.  When comparing, if STRB ends earlier and STRA ends with
     '<', consider them as equal.  */
  if (mode == COMPLETE || (mode == MATCH && c1 == munge ('<')))
    {
      if (c2 == '\0')
	return 0;
    }

  return c1 < c2 ? -1 : 1;
}

#if GDB_SELF_TEST

namespace {

void
test_compare ()
{
  /* Convenience aliases.  */
  const auto mode_compare = cooked_index_entry::MATCH;
  const auto mode_sort = cooked_index_entry::SORT;
  const auto mode_complete = cooked_index_entry::COMPLETE;

  SELF_CHECK (cooked_index_entry::compare ("abcd", "abcd",
					   mode_compare) == 0);
  SELF_CHECK (cooked_index_entry::compare ("abcd", "abcd",
					   mode_complete) == 0);

  SELF_CHECK (cooked_index_entry::compare ("abcd", "ABCDE",
					   mode_compare) < 0);
  SELF_CHECK (cooked_index_entry::compare ("ABCDE", "abcd",
					   mode_compare) > 0);
  SELF_CHECK (cooked_index_entry::compare ("abcd", "ABCDE",
					   mode_complete) < 0);
  SELF_CHECK (cooked_index_entry::compare ("ABCDE", "abcd",
					   mode_complete) == 0);

  SELF_CHECK (cooked_index_entry::compare ("name", "name<>",
					   mode_compare) < 0);
  SELF_CHECK (cooked_index_entry::compare ("name<>", "name",
					   mode_compare) == 0);
  SELF_CHECK (cooked_index_entry::compare ("name", "name<>",
					   mode_complete) < 0);
  SELF_CHECK (cooked_index_entry::compare ("name<>", "name",
					   mode_complete) == 0);

  SELF_CHECK (cooked_index_entry::compare ("name<arg>", "name<arg>",
					   mode_compare) == 0);
  SELF_CHECK (cooked_index_entry::compare ("name<arg>", "name<ag>",
					   mode_compare) > 0);
  SELF_CHECK (cooked_index_entry::compare ("name<arg>", "name<arg>",
					   mode_complete) == 0);
  SELF_CHECK (cooked_index_entry::compare ("name<arg>", "name<ag>",
					   mode_complete) > 0);

  SELF_CHECK (cooked_index_entry::compare ("name<arg<more>>",
					   "name<arg<more>>",
					   mode_compare) == 0);

  SELF_CHECK (cooked_index_entry::compare ("name", "name<arg<more>>",
					   mode_compare) < 0);
  SELF_CHECK (cooked_index_entry::compare ("name<arg<more>>", "name",
					   mode_compare) == 0);
  SELF_CHECK (cooked_index_entry::compare ("name<arg<more>>", "name<arg<",
					   mode_compare) > 0);
  SELF_CHECK (cooked_index_entry::compare ("name<arg<more>>", "name<arg<",
					   mode_complete) == 0);

  SELF_CHECK (cooked_index_entry::compare ("", "abcd", mode_compare) < 0);
  SELF_CHECK (cooked_index_entry::compare ("", "abcd", mode_complete) < 0);
  SELF_CHECK (cooked_index_entry::compare ("abcd", "", mode_compare) > 0);
  SELF_CHECK (cooked_index_entry::compare ("abcd", "", mode_complete) == 0);

  SELF_CHECK (cooked_index_entry::compare ("func", "func<type>",
					   mode_sort) < 0);
  SELF_CHECK (cooked_index_entry::compare ("func<type>", "func1",
					   mode_sort) < 0);
}

} /* anonymous namespace */

#endif /* GDB_SELF_TEST */

/* See cooked-index.h.  */

const char *
cooked_index_entry::full_name (struct obstack *storage, bool for_main) const
{
  const char *local_name = for_main ? name : canonical;

  if ((flags & IS_LINKAGE) != 0 || parent_entry == nullptr)
    return local_name;

  const char *sep = nullptr;
  switch (per_cu->lang ())
    {
    case language_cplus:
    case language_rust:
      sep = "::";
      break;

    case language_go:
    case language_d:
    case language_ada:
      sep = ".";
      break;

    default:
      return local_name;
    }

  parent_entry->write_scope (storage, sep, for_main);
  obstack_grow0 (storage, local_name, strlen (local_name));
  return (const char *) obstack_finish (storage);
}

/* See cooked-index.h.  */

void
cooked_index_entry::write_scope (struct obstack *storage,
				 const char *sep,
				 bool for_main) const
{
  if (parent_entry != nullptr)
    parent_entry->write_scope (storage, sep, for_main);
  const char *local_name = for_main ? name : canonical;
  obstack_grow (storage, local_name, strlen (local_name));
  obstack_grow (storage, sep, strlen (sep));
}

/* See cooked-index.h.  */

const cooked_index_entry *
cooked_index_shard::add (sect_offset die_offset, enum dwarf_tag tag,
			 cooked_index_flag flags, const char *name,
			 const cooked_index_entry *parent_entry,
			 dwarf2_per_cu_data *per_cu)
{
  cooked_index_entry *result = create (die_offset, tag, flags, 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;

  return result;
}

/* See cooked-index.h.  */

void
cooked_index_shard::finalize ()
{
  m_future = gdb::thread_pool::g_thread_pool->post_task ([this] ()
    {
      do_finalize ();
    });
}

/* See cooked-index.h.  */

gdb::unique_xmalloc_ptr<char>
cooked_index_shard::handle_gnat_encoded_entry (cooked_index_entry *entry,
					       htab_t gnat_entries)
{
  std::string canonical = ada_decode (entry->name, false, false);
  if (canonical.empty ())
    return {};
  std::vector<gdb::string_view> names = split_name (canonical.c_str (),
						    split_style::DOT);
  gdb::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)
	{
	  gdb::unique_xmalloc_ptr<char> new_name
	    = make_unique_xstrndup (name.data (), name.length ());
	  last = create (entry->die_offset, DW_TAG_namespace,
			 0, new_name.get (), parent,
			 entry->per_cu);
	  last->canonical = last->name;
	  m_names.push_back (std::move (new_name));
	  *slot = last;
	}

      parent = last;
    }

  entry->parent_entry = parent;
  return make_unique_xstrndup (tail.data (), tail.length ());
}

/* See cooked-index.h.  */

void
cooked_index_shard::do_finalize ()
{
  auto hash_name_ptr = [] (const void *p)
    {
      const cooked_index_entry *entry = (const cooked_index_entry *) p;
      return htab_hash_pointer (entry->name);
    };

  auto eq_name_ptr = [] (const void *a, const void *b) -> int
    {
      const cooked_index_entry *ea = (const cooked_index_entry *) a;
      const cooked_index_entry *eb = (const cooked_index_entry *) b;
      return ea->name == eb->name;
    };

  /* 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.  */
  htab_up seen_names (htab_create_alloc (10, hash_name_ptr, eq_name_ptr,
					 nullptr, xcalloc, xfree));

  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 gdb::string_view *sv = (const gdb::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));

  for (cooked_index_entry *entry : m_entries)
    {
      /* 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->per_cu->lang () == language_ada)
	{
	  gdb::unique_xmalloc_ptr<char> canon_name
	    = handle_gnat_encoded_entry (entry, gnat_entries.get ());
	  if (canon_name == nullptr)
	    entry->canonical = entry->name;
	  else
	    {
	      entry->canonical = canon_name.get ();
	      m_names.push_back (std::move (canon_name));
	    }
	}
      else if (entry->per_cu->lang () == language_cplus
	       || entry->per_cu->lang () == language_c)
	{
	  void **slot = htab_find_slot (seen_names.get (), entry,
					INSERT);
	  if (*slot == nullptr)
	    {
	      gdb::unique_xmalloc_ptr<char> canon_name
		= (entry->per_cu->lang () == language_cplus
		   ? cp_canonicalize_string (entry->name)
		   : c_canonicalize_name (entry->name));
	      if (canon_name == nullptr)
		entry->canonical = entry->name;
	      else
		{
		  entry->canonical = canon_name.get ();
		  m_names.push_back (std::move (canon_name));
		}
	      *slot = entry;
	    }
	  else
	    {
	      const cooked_index_entry *other
		= (const cooked_index_entry *) *slot;
	      entry->canonical = other->canonical;
	    }
	}
      else
	entry->canonical = entry->name;
    }

  m_names.shrink_to_fit ();
  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.h.  */

cooked_index_shard::range
cooked_index_shard::find (const std::string &name, bool completing) const
{
  wait ();

  cooked_index_entry::comparison_mode mode = (completing
					      ? cooked_index_entry::COMPLETE
					      : cooked_index_entry::MATCH);

  auto lower = std::lower_bound (m_entries.cbegin (), m_entries.cend (), name,
				 [=] (const cooked_index_entry *entry,
				      const std::string &n)
  {
    return cooked_index_entry::compare (entry->canonical, n.c_str (), mode) < 0;
  });

  auto upper = std::upper_bound (m_entries.cbegin (), m_entries.cend (), name,
				 [=] (const std::string &n,
				      const cooked_index_entry *entry)
  {
    return cooked_index_entry::compare (entry->canonical, n.c_str (), mode) > 0;
  });

  return range (lower, upper);
}

/* See cooked-index.h.  */

void
cooked_index_shard::wait (bool allow_quit) const
{
  if (allow_quit)
    {
      std::chrono::milliseconds duration { 15 };
      while (m_future.wait_for (duration) == gdb::future_status::timeout)
	QUIT;
    }
  else
    m_future.wait ();
}

cooked_index::cooked_index (vec_type &&vec)
  : m_vector (std::move (vec))
{
  for (auto &idx : m_vector)
    idx->finalize ();

  /* ACTIVE_VECTORS is not locked, and this assert ensures that this
     will be caught if ever moved to the background.  */
  gdb_assert (is_main_thread ());
  active_vectors.insert (this);
}

/* See cooked-index.h.  */

void
cooked_index::start_writing_index (dwarf2_per_bfd *per_bfd)
{
  /* This must be set after all the finalization tasks have been
     started, because it may call 'wait'.  */
  m_write_future
    = gdb::thread_pool::g_thread_pool->post_task ([this, per_bfd] ()
	{
	  maybe_write_index (per_bfd);
	});
}

cooked_index::~cooked_index ()
{
  /* The 'finalize' method may be run in a different thread.  If
     this object is destroyed before this completes, then the method
     will end up writing to freed memory.  Waiting for this to
     complete avoids this problem; and the cost seems ignorable
     because creating and immediately destroying the debug info is a
     relatively rare thing to do.  */
  for (auto &item : m_vector)
    item->wait (false);

  /* Likewise for the index-creating future, though this one must also
     waited for by the per-BFD object to ensure the required data
     remains live.  */
  wait_completely ();

  /* Remove our entry from the global list.  See the assert in the
     constructor to understand this.  */
  gdb_assert (is_main_thread ());
  active_vectors.erase (this);
}

/* See cooked-index.h.  */

dwarf2_per_cu_data *
cooked_index::lookup (CORE_ADDR addr)
{
  for (const auto &index : m_vector)
    {
      dwarf2_per_cu_data *result = index->lookup (addr);
      if (result != nullptr)
	return result;
    }
  return nullptr;
}

/* See cooked-index.h.  */

std::vector<const addrmap *>
cooked_index::get_addrmaps () const
{
  std::vector<const addrmap *> result;
  for (const auto &index : m_vector)
    result.push_back (index->m_addrmap);
  return result;
}

/* See cooked-index.h.  */

cooked_index::range
cooked_index::find (const std::string &name, bool completing) const
{
  std::vector<cooked_index_shard::range> result_range;
  result_range.reserve (m_vector.size ());
  for (auto &entry : m_vector)
    result_range.push_back (entry->find (name, completing));
  return range (std::move (result_range));
}

/* See cooked-index.h.  */

const cooked_index_entry *
cooked_index::get_main () const
{
  const cooked_index_entry *result = nullptr;

  for (const auto &index : m_vector)
    {
      const cooked_index_entry *entry = index->get_main ();
      /* Choose the first "main" we see.  The choice among several is
	 arbitrary.  See the comment by the sole caller to understand
	 the rationale for filtering by language.  */
      if (entry != nullptr
	  && !language_requires_canonicalization (entry->per_cu->lang ()))
	{
	  result = entry;
	  break;
	}
    }

  return result;
}

/* See cooked-index.h.  */

void
cooked_index::dump (gdbarch *arch) const
{
  /* Ensure the index is done building.  */
  this->wait ();

  gdb_printf ("  entries:\n");
  gdb_printf ("\n");

  size_t i = 0;
  for (const cooked_index_entry *entry : this->all_entries ())
    {
      QUIT;

      gdb_printf ("    [%zu] ((cooked_index_entry *) %p)\n", i++, entry);
      gdb_printf ("    name:       %s\n", entry->name);
      gdb_printf ("    canonical:  %s\n", entry->canonical);
      gdb_printf ("    DWARF tag:  %s\n", dwarf_tag_name (entry->tag));
      gdb_printf ("    flags:      %s\n", to_string (entry->flags).c_str ());
      gdb_printf ("    DIE offset: 0x%" PRIx64 "\n",
		  to_underlying (entry->die_offset));

      if (entry->parent_entry != nullptr)
	gdb_printf ("    parent:     ((cooked_index_entry *) %p) [%s]\n",
		    entry->parent_entry, entry->parent_entry->name);
      else
	gdb_printf ("    parent:     ((cooked_index_entry *) 0)\n");

      gdb_printf ("\n");
    }

  const cooked_index_entry *main_entry = this->get_main ();
  if (main_entry != nullptr)
    gdb_printf ("  main: ((cooked_index_entry *) %p) [%s]\n", main_entry,
		  main_entry->name);
  else
    gdb_printf ("  main: ((cooked_index_entry *) 0)\n");

  gdb_printf ("\n");
  gdb_printf ("  address maps:\n");
  gdb_printf ("\n");

  std::vector<const addrmap *> addrmaps = this->get_addrmaps ();
  for (i = 0; i < addrmaps.size (); ++i)
    {
      const addrmap &addrmap = *addrmaps[i];

      gdb_printf ("    [%zu] ((addrmap *) %p)\n", i, &addrmap);
      gdb_printf ("\n");

      addrmap.foreach ([arch] (CORE_ADDR start_addr, const void *obj)
	{
	  QUIT;

	  const char *start_addr_str = paddress (arch, start_addr);

	  if (obj != nullptr)
	    {
	      const dwarf2_per_cu_data *per_cu
		= static_cast<const dwarf2_per_cu_data *> (obj);
	      gdb_printf ("      [%s] ((dwarf2_per_cu_data *) %p)\n",
			  start_addr_str, per_cu);
	    }
	  else
	    gdb_printf ("      [%s] ((dwarf2_per_cu_data *) 0)\n",
			start_addr_str);

	  return 0;
	});

      gdb_printf ("\n");
    }
}

void
cooked_index::maybe_write_index (dwarf2_per_bfd *per_bfd)
{
  /* Wait for finalization.  */
  wait ();

  /* (maybe) store an index in the cache.  */
  global_index_cache.store (per_bfd);
}

/* Wait for all the index cache entries to be written before gdb
   exits.  */
static void
wait_for_index_cache (int)
{
  gdb_assert (is_main_thread ());
  for (cooked_index *item : active_vectors)
    item->wait_completely ();
}

/* A maint command to wait for the cache.  */

static void
maintenance_wait_for_index_cache (const char *args, int from_tty)
{
  wait_for_index_cache (0);
}

void _initialize_cooked_index ();
void
_initialize_cooked_index ()
{
#if GDB_SELF_TEST
  selftests::register_test ("cooked_index_entry::compare", test_compare);
#endif

  add_cmd ("wait-for-index-cache", class_maintenance,
	   maintenance_wait_for_index_cache, _("\
Wait until all pending writes to the index cache have completed.\n\
Usage: maintenance wait-for-index-cache"),
	   &maintenancelist);

  gdb::observers::gdb_exiting.attach (wait_for_index_cache, "cooked-index");
}