Fork GCC's hash-table.h for use in GDB

And use it at one callsite in dwarf2read.

gdb/Makefile.in

@@ -1037,6 +1037,7 @@ COMMON_SFILES = \
 	go-lang.c \
 	go-typeprint.c \
 	go-valprint.c \
+	hash-table.c \
 	inf-child.c \
 	inf-loop.c \
 	infcall.c \

gdb/dwarf2read.c

@@ -90,6 +90,7 @@
 #include <forward_list>
 #include "rust-lang.h"
 #include "gdbsupport/pathstuff.h"
+#include "hash-map.h"
 
 /* When == 1, print basic high level tracing messages.
    When > 1, be more verbose.
@@ -5076,12 +5077,8 @@ dw_expand_symtabs_matching_file_matcher
 
   objfile *const objfile = dwarf2_per_objfile->objfile;
 
-  htab_up visited_found (htab_create_alloc (10, htab_hash_pointer,
-					    htab_eq_pointer,
-					    NULL, xcalloc, xfree));
-  htab_up visited_not_found (htab_create_alloc (10, htab_hash_pointer,
-						htab_eq_pointer,
-						NULL, xcalloc, xfree));
+  hash_table<nofree_ptr_hash <quick_file_names>> visited_found (10);
+  hash_table<nofree_ptr_hash <quick_file_names>> visited_not_found (10);
 
   /* The rule is CUs specify all the files, including those used by
      any TU, so there's no need to scan TUs here.  */
@@ -5100,9 +5097,9 @@ dw_expand_symtabs_matching_file_matcher
       if (file_data == NULL)
 	continue;
 
-      if (htab_find (visited_not_found.get (), file_data) != NULL)
+      if (visited_not_found.find_slot (file_data, NO_INSERT) != NULL)
 	continue;
-      else if (htab_find (visited_found.get (), file_data) != NULL)
+      else if (visited_found.find_slot (file_data, NO_INSERT) != NULL)
 	{
 	  per_cu->v.quick->mark = 1;
 	  continue;
@@ -5132,12 +5129,10 @@ dw_expand_symtabs_matching_file_matcher
 	      break;
 	    }
 	}
-
-      void **slot = htab_find_slot (per_cu->v.quick->mark
-				    ? visited_found.get ()
-				    : visited_not_found.get (),
-				    file_data, INSERT);
-      *slot = file_data;
+      if (per_cu->v.quick->mark)
+	*visited_found.find_slot (file_data, INSERT) = file_data;
+      else
+	*visited_not_found.find_slot (file_data, INSERT) = file_data;
     }
 }
 

gdb/hash-map-traits.h

@@ -0,0 +1,188 @@
+/* A hash map traits.
+   Copyright (C) 2015-2019 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC 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, or (at your option) any later
+version.
+
+GCC 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 GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef HASH_MAP_TRAITS_H
+#define HASH_MAP_TRAITS_H
+
+/* Bacause mem-stats.h uses default hashmap traits, we have to
+   put the class to this separate header file.  */
+
+#include "hash-traits.h"
+
+/* Implement hash_map traits for a key with hash traits H.  Empty and
+   deleted map entries are represented as empty and deleted keys.  */
+
+template <typename H, typename Value>
+struct simple_hashmap_traits
+{
+  typedef typename H::value_type key_type;
+  static const bool maybe_mx = true;
+  static inline hashval_t hash (const key_type &);
+  static inline bool equal_keys (const key_type &, const key_type &);
+  template <typename T> static inline void remove (T &);
+  template <typename T> static inline bool is_empty (const T &);
+  template <typename T> static inline bool is_deleted (const T &);
+  template <typename T> static inline void mark_empty (T &);
+  template <typename T> static inline void mark_deleted (T &);
+};
+
+template <typename H, typename Value>
+inline hashval_t
+simple_hashmap_traits <H, Value>::hash (const key_type &h)
+{
+  return H::hash (h);
+}
+
+template <typename H, typename Value>
+inline bool
+simple_hashmap_traits <H, Value>::equal_keys (const key_type &k1,
+					      const key_type &k2)
+{
+  return H::equal (k1, k2);
+}
+
+template <typename H, typename Value>
+template <typename T>
+inline void
+simple_hashmap_traits <H, Value>::remove (T &entry)
+{
+  H::remove (entry.m_key);
+  entry.m_value.~Value ();
+}
+
+template <typename H, typename Value>
+template <typename T>
+inline bool
+simple_hashmap_traits <H, Value>::is_empty (const T &entry)
+{
+  return H::is_empty (entry.m_key);
+}
+
+template <typename H, typename Value>
+template <typename T>
+inline bool
+simple_hashmap_traits <H, Value>::is_deleted (const T &entry)
+{
+  return H::is_deleted (entry.m_key);
+}
+
+template <typename H, typename Value>
+template <typename T>
+inline void
+simple_hashmap_traits <H, Value>::mark_empty (T &entry)
+{
+  H::mark_empty (entry.m_key);
+}
+
+template <typename H, typename Value>
+template <typename T>
+inline void
+simple_hashmap_traits <H, Value>::mark_deleted (T &entry)
+{
+  H::mark_deleted (entry.m_key);
+}
+
+template <typename H, typename Value>
+struct simple_cache_map_traits: public simple_hashmap_traits<H,Value>
+{
+  static const bool maybe_mx = false;
+};
+
+/* Implement traits for a hash_map with values of type Value for cases
+   in which the key cannot represent empty and deleted slots.  Instead
+   record empty and deleted entries in Value.  Derived classes must
+   implement the hash and equal_keys functions.  */
+
+template <typename Value>
+struct unbounded_hashmap_traits
+{
+  template <typename T> static inline void remove (T &);
+  template <typename T> static inline bool is_empty (const T &);
+  template <typename T> static inline bool is_deleted (const T &);
+  template <typename T> static inline void mark_empty (T &);
+  template <typename T> static inline void mark_deleted (T &);
+};
+
+template <typename Value>
+template <typename T>
+inline void
+unbounded_hashmap_traits <Value>::remove (T &entry)
+{
+  default_hash_traits <Value>::remove (entry.m_value);
+}
+
+template <typename Value>
+template <typename T>
+inline bool
+unbounded_hashmap_traits <Value>::is_empty (const T &entry)
+{
+  return default_hash_traits <Value>::is_empty (entry.m_value);
+}
+
+template <typename Value>
+template <typename T>
+inline bool
+unbounded_hashmap_traits <Value>::is_deleted (const T &entry)
+{
+  return default_hash_traits <Value>::is_deleted (entry.m_value);
+}
+
+template <typename Value>
+template <typename T>
+inline void
+unbounded_hashmap_traits <Value>::mark_empty (T &entry)
+{
+  default_hash_traits <Value>::mark_empty (entry.m_value);
+}
+
+template <typename Value>
+template <typename T>
+inline void
+unbounded_hashmap_traits <Value>::mark_deleted (T &entry)
+{
+  default_hash_traits <Value>::mark_deleted (entry.m_value);
+}
+
+/* Implement traits for a hash_map from integer type Key to Value in
+   cases where Key has no spare values for recording empty and deleted
+   slots.  */
+
+template <typename Key, typename Value>
+struct unbounded_int_hashmap_traits : unbounded_hashmap_traits <Value>
+{
+  typedef Key key_type;
+  static inline hashval_t hash (Key);
+  static inline bool equal_keys (Key, Key);
+};
+
+template <typename Key, typename Value>
+inline hashval_t
+unbounded_int_hashmap_traits <Key, Value>::hash (Key k)
+{
+  return k;
+}
+
+template <typename Key, typename Value>
+inline bool
+unbounded_int_hashmap_traits <Key, Value>::equal_keys (Key k1, Key k2)
+{
+  return k1 == k2;
+}
+
+#endif // HASH_MAP_TRAITS_H

gdb/hash-map.h

@@ -0,0 +1,220 @@
+/* A type-safe hash map.
+   Copyright (C) 2014-2019 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC 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, or (at your option) any later
+version.
+
+GCC 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 GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+
+#ifndef hash_map_h
+#define hash_map_h
+
+#include "hash-table.h"
+
+/* Class hash_map is a hash-value based container mapping objects of
+   KeyId type to those of the Value type.
+   Both KeyId and Value may be non-trivial (non-POD) types provided
+   a suitabe Traits class.  A few default Traits specializations are
+   provided for basic types such as integers, pointers, and std::pair.
+   Inserted elements are value-initialized either to zero for POD types
+   or by invoking their default ctor.  Removed elements are destroyed
+   by invoking their dtor.   On hash_map destruction all elements are
+   removed.  Objects of hash_map type are copy-constructible but not
+   assignable.  */
+
+template<typename KeyId, typename Value,
+	 typename Traits /* = simple_hashmap_traits<default_hash_traits<Key>,
+			                            Value> */>
+class hash_map
+{
+  typedef typename Traits::key_type Key;
+  struct hash_entry
+  {
+    Key m_key;
+    Value m_value;
+
+    typedef hash_entry value_type;
+    typedef Key compare_type;
+
+    static hashval_t hash (const hash_entry &e)
+      {
+       	return Traits::hash (e.m_key);
+      }
+
+    static bool equal (const hash_entry &a, const Key &b)
+       	{
+	  return Traits::equal_keys (a.m_key, b);
+       	}
+
+    static void remove (hash_entry &e) { Traits::remove (e); }
+
+    static void mark_deleted (hash_entry &e) { Traits::mark_deleted (e); }
+
+    static bool is_deleted (const hash_entry &e)
+      {
+       	return Traits::is_deleted (e);
+      }
+
+    static void mark_empty (hash_entry &e) { Traits::mark_empty (e); }
+    static bool is_empty (const hash_entry &e) { return Traits::is_empty (e); }
+  };
+
+public:
+  explicit hash_map (size_t n = 13,
+		     bool sanitize_eq_and_hash = true)
+    : m_table (n, sanitize_eq_and_hash)
+  {
+  }
+
+  explicit hash_map (const hash_map &h,
+		     bool sanitize_eq_and_hash = true)
+    : m_table (h.m_table, sanitize_eq_and_hash) {}
+
+  /* If key k isn't already in the map add key k with value v to the map, and
+     return false.  Otherwise set the value of the entry for key k to be v and
+     return true.  */
+
+  bool put (const Key &k, const Value &v)
+    {
+      hash_entry *e = m_table.find_slot_with_hash (k, Traits::hash (k),
+						   INSERT);
+      bool ins = hash_entry::is_empty (*e);
+      if (ins)
+	{
+	  e->m_key = k;
+	  new ((void *) &e->m_value) Value (v);
+	}
+      else
+	e->m_value = v;
+
+      return !ins;
+    }
+
+  /* if the passed in key is in the map return its value otherwise NULL.  */
+
+  Value *get (const Key &k)
+    {
+      hash_entry &e = m_table.find_with_hash (k, Traits::hash (k));
+      return Traits::is_empty (e) ? NULL : &e.m_value;
+    }
+
+  /* Return a reference to the value for the passed in key, creating the entry
+     if it doesn't already exist.  If existed is not NULL then it is set to
+     false if the key was not previously in the map, and true otherwise.  */
+
+  Value &get_or_insert (const Key &k, bool *existed = NULL)
+    {
+      hash_entry *e = m_table.find_slot_with_hash (k, Traits::hash (k),
+						   INSERT);
+      bool ins = Traits::is_empty (*e);
+      if (ins)
+	{
+	  e->m_key = k;
+	  new ((void *)&e->m_value) Value ();
+	}
+
+      if (existed != NULL)
+	*existed = !ins;
+
+      return e->m_value;
+    }
+
+  void remove (const Key &k)
+    {
+      m_table.remove_elt_with_hash (k, Traits::hash (k));
+    }
+
+  /* Call the call back on each pair of key and value with the passed in
+     arg.  */
+
+  template<typename Arg, bool (*f)(const typename Traits::key_type &,
+				   const Value &, Arg)>
+  void traverse (Arg a) const
+    {
+      for (typename hash_table<hash_entry>::iterator iter = m_table.begin ();
+	   iter != m_table.end (); ++iter)
+	f ((*iter).m_key, (*iter).m_value, a);
+    }
+
+  template<typename Arg, bool (*f)(const typename Traits::key_type &,
+				   Value *, Arg)>
+  void traverse (Arg a) const
+    {
+      for (typename hash_table<hash_entry>::iterator iter = m_table.begin ();
+	   iter != m_table.end (); ++iter)
+	if (!f ((*iter).m_key, &(*iter).m_value, a))
+	  break;
+    }
+
+  size_t elements () const { return m_table.elements (); }
+
+  void empty () { m_table.empty(); }
+
+  /* Return true when there are no elements in this hash map.  */
+  bool is_empty () const { return m_table.is_empty (); }
+
+  class iterator
+  {
+  public:
+    explicit iterator (const typename hash_table<hash_entry>::iterator &iter) :
+      m_iter (iter) {}
+
+    iterator &operator++ ()
+    {
+      ++m_iter;
+      return *this;
+    }
+
+    /* Can't use std::pair here, because GCC before 4.3 don't handle
+       std::pair where template parameters are references well.
+       See PR86739.  */
+    class reference_pair {
+    public:
+      const Key &first;
+      Value &second;
+
+      reference_pair (const Key &key, Value &value) : first (key), second (value) {}
+
+      template <typename K, typename V>
+      operator std::pair<K, V> () const { return std::pair<K, V> (first, second); }
+    };
+
+    reference_pair operator* ()
+    {
+      hash_entry &e = *m_iter;
+      return reference_pair (e.m_key, e.m_value);
+    }
+
+    bool
+    operator != (const iterator &other) const
+    {
+      return m_iter != other.m_iter;
+    }
+
+  private:
+    typename hash_table<hash_entry>::iterator m_iter;
+  };
+
+  /* Standard iterator retrieval methods.  */
+
+  iterator  begin () const { return iterator (m_table.begin ()); }
+  iterator end () const { return iterator (m_table.end ()); }
+
+private:
+
+  hash_table<hash_entry> m_table;
+};
+
+#endif

gdb/hash-table.c

@@ -0,0 +1,97 @@
+/* A type-safe hash table template.
+   Copyright (C) 2012-2019 Free Software Foundation, Inc.
+   Contributed by Lawrence Crowl <crowl@google.com>
+
+This file is part of GCC.
+
+GCC 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, or (at your option) any later
+version.
+
+GCC 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 GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+
+/* This file implements a typed hash table.
+   The implementation borrows from libiberty's hashtab.  */
+
+#include "defs.h"
+#include "gdbtypes.h"
+#include "hash-table.h"
+
+/* Table of primes and multiplicative inverses.
+
+   Note that these are not minimally reduced inverses.  Unlike when generating
+   code to divide by a constant, we want to be able to use the same algorithm
+   all the time.  All of these inverses (are implied to) have bit 32 set.
+
+   For the record, here's the function that computed the table; it's a 
+   vastly simplified version of the function of the same name from gcc.  */
+
+struct prime_ent const prime_tab[] = {
+  {          7, 0x24924925, 0x9999999b, 2 },
+  {         13, 0x3b13b13c, 0x745d1747, 3 },
+  {         31, 0x08421085, 0x1a7b9612, 4 },
+  {         61, 0x0c9714fc, 0x15b1e5f8, 5 },
+  {        127, 0x02040811, 0x0624dd30, 6 },
+  {        251, 0x05197f7e, 0x073260a5, 7 },
+  {        509, 0x01824366, 0x02864fc8, 8 },
+  {       1021, 0x00c0906d, 0x014191f7, 9 },
+  {       2039, 0x0121456f, 0x0161e69e, 10 },
+  {       4093, 0x00300902, 0x00501908, 11 },
+  {       8191, 0x00080041, 0x00180241, 12 },
+  {      16381, 0x000c0091, 0x00140191, 13 },
+  {      32749, 0x002605a5, 0x002a06e6, 14 },
+  {      65521, 0x000f00e2, 0x00110122, 15 },
+  {     131071, 0x00008001, 0x00018003, 16 },
+  {     262139, 0x00014002, 0x0001c004, 17 },
+  {     524287, 0x00002001, 0x00006001, 18 },
+  {    1048573, 0x00003001, 0x00005001, 19 },
+  {    2097143, 0x00004801, 0x00005801, 20 },
+  {    4194301, 0x00000c01, 0x00001401, 21 },
+  {    8388593, 0x00001e01, 0x00002201, 22 },
+  {   16777213, 0x00000301, 0x00000501, 23 },
+  {   33554393, 0x00001381, 0x00001481, 24 },
+  {   67108859, 0x00000141, 0x000001c1, 25 },
+  {  134217689, 0x000004e1, 0x00000521, 26 },
+  {  268435399, 0x00000391, 0x000003b1, 27 },
+  {  536870909, 0x00000019, 0x00000029, 28 },
+  { 1073741789, 0x0000008d, 0x00000095, 29 },
+  { 2147483647, 0x00000003, 0x00000007, 30 },
+  /* Avoid "decimal constant so large it is unsigned" for 4294967291.  */
+  { 0xfffffffb, 0x00000006, 0x00000008, 31 }
+};
+
+/* Limit number of comparisons when calling hash_table<>::verify.  */
+unsigned int hash_table_sanitize_eq_limit;
+
+/* The following function returns an index into the above table of the
+   nearest prime number which is greater than N, and near a power of two. */
+
+unsigned int
+hash_table_higher_prime_index (unsigned long n)
+{
+  unsigned int low = 0;
+  unsigned int high = sizeof (prime_tab) / sizeof (prime_tab[0]);
+
+  while (low != high)
+    {
+      unsigned int mid = low + (high - low) / 2;
+      if (n > prime_tab[mid].prime)
+	low = mid + 1;
+      else
+	high = mid;
+    }
+
+  /* If we've run out of primes, abort.  */
+  gdb_assert (n <= prime_tab[low].prime);
+
+  return low;
+}

gdb/hash-traits.h

@@ -0,0 +1,322 @@
+/* Traits for hashable types.
+   Copyright (C) 2014-2019 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC 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, or (at your option) any later
+version.
+
+GCC 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 GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef hash_traits_h
+#define hash_traits_h
+
+/* Helpful type for removing with free.  */
+
+template <typename Type>
+struct typed_free_remove
+{
+  static inline void remove (Type *p);
+};
+
+
+/* Remove with free.  */
+
+template <typename Type>
+inline void
+typed_free_remove <Type>::remove (Type *p)
+{
+  free (p);
+}
+
+/* Helpful type for removing with delete.  */
+
+template <typename Type>
+struct typed_delete_remove
+{
+  static inline void remove (Type *p);
+};
+
+
+/* Remove with delete.  */
+
+template <typename Type>
+inline void
+typed_delete_remove <Type>::remove (Type *p)
+{
+  delete p;
+}
+
+/* Helpful type for a no-op remove.  */
+
+template <typename Type>
+struct typed_noop_remove
+{
+  static inline void remove (Type &);
+};
+
+
+/* Remove doing nothing.  */
+
+template <typename Type>
+inline void
+typed_noop_remove <Type>::remove (Type &)
+{
+}
+
+
+/* Hasher for integer type Type in which Empty is a spare value that can be
+   used to mark empty slots.  If Deleted != Empty then Deleted is another
+   spare value that can be used for deleted slots; if Deleted == Empty then
+   hash table entries cannot be deleted.  */
+
+template <typename Type, Type Empty, Type Deleted = Empty>
+struct int_hash : typed_noop_remove <Type>
+{
+  typedef Type value_type;
+  typedef Type compare_type;
+
+  static inline hashval_t hash (value_type);
+  static inline bool equal (value_type existing, value_type candidate);
+  static inline void mark_deleted (Type &);
+  static inline void mark_empty (Type &);
+  static inline bool is_deleted (Type);
+  static inline bool is_empty (Type);
+};
+
+template <typename Type, Type Empty, Type Deleted>
+inline hashval_t
+int_hash <Type, Empty, Deleted>::hash (value_type x)
+{
+  return x;
+}
+
+template <typename Type, Type Empty, Type Deleted>
+inline bool
+int_hash <Type, Empty, Deleted>::equal (value_type x, value_type y)
+{
+  return x == y;
+}
+
+template <typename Type, Type Empty, Type Deleted>
+inline void
+int_hash <Type, Empty, Deleted>::mark_deleted (Type &x)
+{
+  gdb_assert (Empty != Deleted);
+  x = Deleted;
+}
+
+template <typename Type, Type Empty, Type Deleted>
+inline void
+int_hash <Type, Empty, Deleted>::mark_empty (Type &x)
+{
+  x = Empty;
+}
+
+template <typename Type, Type Empty, Type Deleted>
+inline bool
+int_hash <Type, Empty, Deleted>::is_deleted (Type x)
+{
+  return Empty != Deleted && x == Deleted;
+}
+
+template <typename Type, Type Empty, Type Deleted>
+inline bool
+int_hash <Type, Empty, Deleted>::is_empty (Type x)
+{
+  return x == Empty;
+}
+
+/* Pointer hasher based on pointer equality.  Other types of pointer hash
+   can inherit this and override the hash and equal functions with some
+   other form of equality (such as string equality).  */
+
+template <typename Type>
+struct pointer_hash
+{
+  typedef Type *value_type;
+  typedef Type *compare_type;
+
+  static inline hashval_t hash (const value_type &);
+  static inline bool equal (const value_type &existing,
+			    const compare_type &candidate);
+  static inline void mark_deleted (Type *&);
+  static inline void mark_empty (Type *&);
+  static inline bool is_deleted (Type *);
+  static inline bool is_empty (Type *);
+};
+
+template <typename Type>
+inline hashval_t
+pointer_hash <Type>::hash (const value_type &candidate)
+{
+  /* This is a really poor hash function, but it is what the current code uses,
+     so I am reusing it to avoid an additional axis in testing.  */
+  return (hashval_t) ((intptr_t)candidate >> 3);
+}
+
+template <typename Type>
+inline bool
+pointer_hash <Type>::equal (const value_type &existing,
+			   const compare_type &candidate)
+{
+  return existing == candidate;
+}
+
+template <typename Type>
+inline void
+pointer_hash <Type>::mark_deleted (Type *&e)
+{
+  e = reinterpret_cast<Type *> (1);
+}
+
+template <typename Type>
+inline void
+pointer_hash <Type>::mark_empty (Type *&e)
+{
+  e = NULL;
+}
+
+template <typename Type>
+inline bool
+pointer_hash <Type>::is_deleted (Type *e)
+{
+  return e == reinterpret_cast<Type *> (1);
+}
+
+template <typename Type>
+inline bool
+pointer_hash <Type>::is_empty (Type *e)
+{
+  return e == NULL;
+}
+
+/* Hasher for "const char *" strings, using string rather than pointer
+   equality.  */
+
+struct string_hash : pointer_hash <const char>
+{
+  static inline hashval_t hash (const char *);
+  static inline bool equal (const char *, const char *);
+};
+
+inline hashval_t
+string_hash::hash (const char *id)
+{
+  return htab_hash_string (id);
+}
+
+inline bool
+string_hash::equal (const char *id1, const char *id2)
+{
+  return strcmp (id1, id2) == 0;
+}
+
+/* Traits for pointer elements that should not be freed when an element
+   is deleted.  */
+
+template <typename T>
+struct nofree_ptr_hash : pointer_hash <T>, typed_noop_remove <T *> {};
+
+/* Traits for pointer elements that should be freed via free() when an
+   element is deleted.  */
+
+template <typename T>
+struct free_ptr_hash : pointer_hash <T>, typed_free_remove <T> {};
+
+/* Traits for pointer elements that should be freed via delete operand when an
+   element is deleted.  */
+
+template <typename T>
+struct delete_ptr_hash : pointer_hash <T>, typed_delete_remove <T> {};
+
+/* Traits for string elements that should not be freed when an element
+   is deleted.  */
+
+struct nofree_string_hash : string_hash, typed_noop_remove <const char *> {};
+
+/* Traits for pairs of values, using the first to record empty and
+   deleted slots.  */
+
+template <typename T1, typename T2>
+struct pair_hash
+{
+  typedef std::pair <typename T1::value_type,
+		     typename T2::value_type> value_type;
+  typedef std::pair <typename T1::compare_type,
+		     typename T2::compare_type> compare_type;
+
+  static inline hashval_t hash (const value_type &);
+  static inline bool equal (const value_type &, const compare_type &);
+  static inline void remove (value_type &);
+  static inline void mark_deleted (value_type &);
+  static inline void mark_empty (value_type &);
+  static inline bool is_deleted (const value_type &);
+  static inline bool is_empty (const value_type &);
+};
+
+template <typename T1, typename T2>
+inline hashval_t
+pair_hash <T1, T2>::hash (const value_type &x)
+{
+  return iterative_hash_hashval_t (T1::hash (x.first), T2::hash (x.second));
+}
+
+template <typename T1, typename T2>
+inline bool
+pair_hash <T1, T2>::equal (const value_type &x, const compare_type &y)
+{
+  return T1::equal (x.first, y.first) && T2::equal (x.second, y.second);
+}
+
+template <typename T1, typename T2>
+inline void
+pair_hash <T1, T2>::remove (value_type &x)
+{
+  T1::remove (x.first);
+  T2::remove (x.second);
+}
+
+template <typename T1, typename T2>
+inline void
+pair_hash <T1, T2>::mark_deleted (value_type &x)
+{
+  T1::mark_deleted (x.first);
+}
+
+template <typename T1, typename T2>
+inline void
+pair_hash <T1, T2>::mark_empty (value_type &x)
+{
+  T1::mark_empty (x.first);
+}
+
+template <typename T1, typename T2>
+inline bool
+pair_hash <T1, T2>::is_deleted (const value_type &x)
+{
+  return T1::is_deleted (x.first);
+}
+
+template <typename T1, typename T2>
+inline bool
+pair_hash <T1, T2>::is_empty (const value_type &x)
+{
+  return T1::is_empty (x.first);
+}
+
+template <typename T> struct default_hash_traits : T {};
+
+template <typename T>
+struct default_hash_traits <T *> : pointer_hash <T> {};
+
+#endif