85th Cygnus<->FSF quick merge

[gcc.git] / gcc / cp / pt.c

/* Handle parameterized types (templates) for GNU C++.
   Copyright (C) 1992, 93, 94, 95, 1996 Free Software Foundation, Inc.
   Written by Ken Raeburn (raeburn@cygnus.com) while at Watchmaker Computing.
   Rewritten by Jason Merrill (jason@cygnus.com).

This file is part of GNU CC.

GNU CC 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 2, or (at your option)
any later version.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Known bugs or deficiencies include:
   * templates for class static data don't work (methods only)
   * duplicated method templates can crash the compiler
   * interface/impl data is taken from file defining the template
   * all methods must be provided in header files; can't use a source
     file that contains only the method templates and "just win"
 */

#include "config.h"
#include <stdio.h>
#include "obstack.h"

#include "tree.h"
#include "flags.h"
#include "cp-tree.h"
#include "decl.h"
#include "parse.h"
#include "lex.h"
#include "output.h"
#include "defaults.h"

extern struct obstack permanent_obstack;

extern int lineno;
extern char *input_filename;
struct pending_inline *pending_template_expansions;

tree current_template_parms;
HOST_WIDE_INT processing_template_decl;

tree pending_templates;
static tree *template_tail = &pending_templates;

int minimal_parse_mode;

#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free free

static int unify ();

void pop_template_decls ();

tree classtype_mangled_name ();
static char * mangle_class_name_for_template ();
tree tsubst_expr_values ();

/* We've got a template header coming up; push to a new level for storing
   the parms.  */

void
begin_template_parm_list ()
{
  pushlevel (0);
  declare_pseudo_global_level ();
}

/* Process information from new template parameter NEXT and append it to the
   LIST being built.  */
tree
process_template_parm (list, next)
     tree list, next;
{
  tree parm;
  tree decl = 0;
  tree defval;
  int is_type, idx;
  parm = next;
  my_friendly_assert (TREE_CODE (parm) == TREE_LIST, 259);
  defval = TREE_PURPOSE (parm);
  parm = TREE_VALUE (parm);
  is_type = TREE_PURPOSE (parm) == class_type_node;

  if (list)
    {
      tree p = TREE_VALUE (tree_last (list));

      if (TREE_CODE (p) == TYPE_DECL)
        idx = TEMPLATE_TYPE_IDX (TREE_TYPE (p));
      else
        idx = TEMPLATE_CONST_IDX (DECL_INITIAL (p));
      ++idx;
    }
  else
    idx = 0;

  if (!is_type)
    {
      tree tinfo = 0;
      my_friendly_assert (TREE_CODE (TREE_PURPOSE (parm)) == TREE_LIST, 260);
      /* is a const-param */
      parm = grokdeclarator (TREE_VALUE (parm), TREE_PURPOSE (parm),
                             PARM, 0, NULL_TREE, NULL_TREE);
      /* A template parameter is not modifiable.  */
      TREE_READONLY (parm) = 1;
      if (IS_AGGR_TYPE (TREE_TYPE (parm)))
        {
          sorry ("aggregate template parameter types");
          TREE_TYPE (parm) = void_type_node;
        }
      tinfo = make_node (TEMPLATE_CONST_PARM);
      my_friendly_assert (TREE_PERMANENT (tinfo), 260.5);
      if (TREE_PERMANENT (parm) == 0)
        {
          parm = copy_node (parm);
          TREE_PERMANENT (parm) = 1;
        }
      TREE_TYPE (tinfo) = TREE_TYPE (parm);
      decl = build_decl (CONST_DECL, DECL_NAME (parm), TREE_TYPE (parm));
      DECL_INITIAL (decl) = tinfo;
      DECL_INITIAL (parm) = tinfo;
      TEMPLATE_CONST_SET_INFO (tinfo, idx, processing_template_decl + 1);
    }
  else
    {
      tree t = make_lang_type (TEMPLATE_TYPE_PARM);
      CLASSTYPE_GOT_SEMICOLON (t) = 1;
      decl = build_decl (TYPE_DECL, TREE_VALUE (parm), t);
      TYPE_MAIN_DECL (t) = decl;
      parm = decl;
      TEMPLATE_TYPE_SET_INFO (t, idx, processing_template_decl + 1);
    }
  SET_DECL_ARTIFICIAL (decl);
  pushdecl (decl);
  parm = build_tree_list (defval, parm);
  return chainon (list, parm);
}

/* The end of a template parameter list has been reached.  Process the
   tree list into a parameter vector, converting each parameter into a more
   useful form.  Type parameters are saved as IDENTIFIER_NODEs, and others
   as PARM_DECLs.  */

tree
end_template_parm_list (parms)
     tree parms;
{
  int nparms;
  tree parm;
  tree saved_parmlist = make_tree_vec (list_length (parms));

  ++processing_template_decl;
  current_template_parms
    = tree_cons (build_int_2 (0, processing_template_decl),
                 saved_parmlist, current_template_parms);

  for (parm = parms, nparms = 0; parm; parm = TREE_CHAIN (parm), nparms++)
    TREE_VEC_ELT (saved_parmlist, nparms) = parm;

  return saved_parmlist;
}

/* end_template_decl is called after a template declaration is seen.  */

void
end_template_decl ()
{
  /* This matches the pushlevel in begin_template_parm_list.  */
  poplevel (0, 0, 0);

  --processing_template_decl;
  current_template_parms = TREE_CHAIN (current_template_parms);
  (void) get_pending_sizes ();  /* Why? */
}

void
push_template_decl (decl)
     tree decl;
{
  tree header = current_template_parms;
  tree tmpl;
  tree args = NULL_TREE;
  tree info;
  tree ctx = DECL_CONTEXT (decl) ? DECL_CONTEXT (decl) : current_class_type;
  int primary = 0;

  /* Kludge! */
  if (TREE_CODE (decl) == FUNCTION_DECL && DECL_FRIEND_P (decl)
      && DECL_CLASS_CONTEXT (decl))
    ;
  /* Note that this template is a "primary template" */
  else if (! ctx || ! CLASSTYPE_TEMPLATE_INFO (ctx)
      /* || (processing_template_decl > CLASSTYPE_TEMPLATE_LEVEL (ctx)) */)
    primary = 1;

  while (header)
    {
      tree a = copy_node (TREE_VALUE (header));
      int i = TREE_VEC_LENGTH (a);
      TREE_TYPE (a) = NULL_TREE;
      while (i--)
        {
          tree t = TREE_VALUE (TREE_VEC_ELT (a, i));
          if (TREE_CODE (t) == TYPE_DECL)
            t = TREE_TYPE (t);
          else
            t = DECL_INITIAL (t);
          TREE_VEC_ELT (a, i) = t;
        }
      args = tree_cons (TREE_PURPOSE (header), a, args);
      header = TREE_CHAIN (header);
    }
  args = nreverse (args);
  args = TREE_VALUE (args);

  if (! ctx || TYPE_BEING_DEFINED (ctx))
    {
      tmpl = build_lang_decl (TEMPLATE_DECL, DECL_NAME (decl), NULL_TREE);
      DECL_TEMPLATE_PARMS (tmpl) = TREE_VALUE (current_template_parms);
      DECL_CONTEXT (tmpl) = DECL_CONTEXT (decl);
    }
  else
    {
      if (TREE_CODE (decl) == TYPE_DECL)
        tmpl = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (decl));
      else if (! DECL_TEMPLATE_INFO (decl))
        /* A member definition that doesn't match anything in the class.  */
        return;
      else
        tmpl = DECL_TI_TEMPLATE (decl);
    }

  DECL_TEMPLATE_RESULT (tmpl) = decl;
  TREE_TYPE (tmpl) = TREE_TYPE (decl);

  if (! ctx)
    tmpl = pushdecl_top_level (tmpl);

  if (primary)
    TREE_TYPE (DECL_TEMPLATE_PARMS (tmpl)) = tmpl;

  info = perm_tree_cons (tmpl, args, NULL_TREE);

  if (TREE_CODE (decl) == TYPE_DECL)
    {
      CLASSTYPE_TEMPLATE_INFO (TREE_TYPE (tmpl)) = info;
      DECL_NAME (decl) = classtype_mangled_name (TREE_TYPE (decl));
    }
  else if (! DECL_LANG_SPECIFIC (decl))
    cp_error ("template declaration of `%#D'", decl);
  else
    DECL_TEMPLATE_INFO (decl) = info;
}

tree tsubst             PROTO ((tree, tree*, int, tree));

/* Convert all template arguments to their appropriate types, and return
   a vector containing the resulting values.  If any error occurs, return
   error_mark_node.  */
static tree
coerce_template_parms (parms, arglist, in_decl)
     tree parms, arglist;
     tree in_decl;
{
  int nparms, nargs, i, lost = 0;
  tree vec;

  if (arglist == NULL_TREE)
    nargs = 0;
  else if (TREE_CODE (arglist) == TREE_VEC)
    nargs = TREE_VEC_LENGTH (arglist);
  else
    nargs = list_length (arglist);

  nparms = TREE_VEC_LENGTH (parms);

  if (nargs > nparms
      || (nargs < nparms
          && TREE_PURPOSE (TREE_VEC_ELT (parms, nargs)) == NULL_TREE))
    {
      error ("incorrect number of parameters (%d, should be %d)",
             nargs, nparms);
      if (in_decl)
        cp_error_at ("in template expansion for decl `%D'", in_decl);
      return error_mark_node;
    }

  if (arglist && TREE_CODE (arglist) == TREE_VEC)
    vec = copy_node (arglist);
  else
    {
      vec = make_tree_vec (nparms);
      for (i = 0; i < nparms; i++)
        {
          tree arg;

          if (arglist)
            {
              arg = arglist;
              arglist = TREE_CHAIN (arglist);

              if (arg == error_mark_node)
                lost++;
              else
                arg = TREE_VALUE (arg);
            }
          else
            arg = tsubst (TREE_PURPOSE (TREE_VEC_ELT (parms, i)),
                          &TREE_VEC_ELT (vec, 0), i, in_decl);

          TREE_VEC_ELT (vec, i) = arg;
        }
    }
  for (i = 0; i < nparms; i++)
    {
      tree arg = TREE_VEC_ELT (vec, i);
      tree parm = TREE_VALUE (TREE_VEC_ELT (parms, i));
      tree val = 0;
      int is_type, requires_type;

      is_type = TREE_CODE_CLASS (TREE_CODE (arg)) == 't';
      requires_type = TREE_CODE (parm) == TYPE_DECL;

      if (requires_type && ! is_type && TREE_CODE (arg) == SCOPE_REF
          && TREE_CODE (TREE_OPERAND (arg, 0)) == TEMPLATE_TYPE_PARM)
        {
          cp_pedwarn ("to refer to a type member of a template parameter,");
          cp_pedwarn ("  use `typename %E'", arg);
          arg = make_typename_type (TREE_OPERAND (arg, 0),
                                    TREE_OPERAND (arg, 1));
          is_type = 1;
        }
      if (is_type != requires_type)
        {
          if (in_decl)
            {
              cp_error ("type/value mismatch at argument %d in template parameter list for `%D'",
                        i, in_decl);
              if (is_type)
                cp_error ("  expected a constant of type `%T', got `%T'",
                          TREE_TYPE (parm), arg);
              else
                cp_error ("  expected a type, got `%E'", arg);
            }
          lost++;
          TREE_VEC_ELT (vec, i) = error_mark_node;
          continue;
        }
      if (is_type)
        {
          val = groktypename (arg);
          if (! current_template_parms)
            {
              tree t = target_type (val);
              if (IS_AGGR_TYPE (t)
                  && decl_function_context (TYPE_MAIN_DECL (t)))
                {
                  cp_error ("type `%T' composed from a local class is not a valid template-argument", val);
                  return error_mark_node;
                }
            }
        }
      else
        {
          tree t = tsubst (TREE_TYPE (parm), &TREE_VEC_ELT (vec, 0),
                           TREE_VEC_LENGTH (vec), in_decl);
          if (current_template_parms)
            val = arg;
          else
            val = digest_init (t, arg, (tree *) 0);

          if (val == error_mark_node || current_template_parms)
            ;

          /* 14.2: Other template-arguments must be constant-expressions,
             addresses of objects or functions with external linkage, or of
             static class members.  */
          else if (!TREE_CONSTANT (val))
            {
              cp_error ("non-const `%E' cannot be used as template argument",
                        arg);
              val = error_mark_node;
            }
          else if (POINTER_TYPE_P (TREE_TYPE (val))
                   && ! integer_zerop (val)
                   && TREE_CODE (TREE_TYPE (TREE_TYPE (val))) != OFFSET_TYPE
                   && TREE_CODE (TREE_TYPE (TREE_TYPE (val))) != METHOD_TYPE)
            {
              t = val;
              STRIP_NOPS (t);
              if (TREE_CODE (t) == ADDR_EXPR)
                {
                  tree a = TREE_OPERAND (t, 0);
                  STRIP_NOPS (a);
                  if (TREE_CODE (a) == STRING_CST)
                    {
                      cp_error ("string literal %E is not a valid template argument", a);
                      error ("because it is the address of an object with static linkage");
                      val = error_mark_node;
                    }
                  else if (TREE_CODE (a) != VAR_DECL
                           && TREE_CODE (a) != FUNCTION_DECL)
                    goto bad;
                  else if (! DECL_PUBLIC (a))
                    {
                      cp_error ("address of non-extern `%E' cannot be used as template argument", a);
                      val = error_mark_node;
                    }
                }
              else
                {
                bad:
                  cp_error ("`%E' is not a valid template argument", t);
                  error ("it must be %s%s with external linkage",
                         TREE_CODE (TREE_TYPE (val)) == POINTER_TYPE
                         ? "a pointer to " : "",
                         TREE_CODE (TREE_TYPE (TREE_TYPE (val))) == FUNCTION_TYPE
                         ? "a function" : "an object");
                  val = error_mark_node;
                }
            }
        }

      if (val == error_mark_node)
        lost++;

      TREE_VEC_ELT (vec, i) = val;
    }
  if (lost)
    return error_mark_node;
  return vec;
}

int
comp_template_args (oldargs, newargs)
     tree oldargs, newargs;
{
  int i;

  for (i = 0; i < TREE_VEC_LENGTH (oldargs); ++i)
    {
      tree nt = TREE_VEC_ELT (newargs, i);
      tree ot = TREE_VEC_ELT (oldargs, i);

      if (nt == ot)
        continue;
      if (TREE_CODE (nt) != TREE_CODE (ot))
        return 0;
      if (TREE_CODE_CLASS (TREE_CODE (ot)) == 't' && comptypes (ot, nt, 1))
        continue;
      if (TREE_CODE (ot) == TEMPLATE_CONST_PARM
          && TEMPLATE_CONST_IDX (nt) == TEMPLATE_CONST_IDX (ot))
        continue;
      return 0;
    }
  return 1;
}

/* Given class template name and parameter list, produce a user-friendly name
   for the instantiation.  */
static char *
mangle_class_name_for_template (name, parms, arglist)
     char *name;
     tree parms, arglist;
{
  static struct obstack scratch_obstack;
  static char *scratch_firstobj;
  int i, nparms;

  if (!scratch_firstobj)
    gcc_obstack_init (&scratch_obstack);
  else
    obstack_free (&scratch_obstack, scratch_firstobj);
  scratch_firstobj = obstack_alloc (&scratch_obstack, 1);

#if 0
#define buflen  sizeof(buf)
#define check   if (bufp >= buf+buflen-1) goto too_long
#define ccat(c) *bufp++=(c); check
#define advance bufp+=strlen(bufp); check
#define cat(s)  strncpy(bufp, s, buf+buflen-bufp-1); advance
#else
#define check
#define ccat(c) obstack_1grow (&scratch_obstack, (c));
#define advance
#define cat(s)  obstack_grow (&scratch_obstack, (s), strlen (s))
#endif

  cat (name);
  ccat ('<');
  nparms = TREE_VEC_LENGTH (parms);
  my_friendly_assert (nparms == TREE_VEC_LENGTH (arglist), 268);
  for (i = 0; i < nparms; i++)
    {
      tree parm = TREE_VALUE (TREE_VEC_ELT (parms, i));
      tree arg = TREE_VEC_ELT (arglist, i);

      if (i)
        ccat (',');

      if (TREE_CODE (parm) == TYPE_DECL)
        {
          cat (type_as_string (arg, 0));
          continue;
        }
      else
        my_friendly_assert (TREE_CODE (parm) == PARM_DECL, 269);

      if (TREE_CODE (arg) == TREE_LIST)
        {
          /* New list cell was built because old chain link was in
             use.  */
          my_friendly_assert (TREE_PURPOSE (arg) == NULL_TREE, 270);
          arg = TREE_VALUE (arg);
        }
      /* No need to check arglist against parmlist here; we did that
         in coerce_template_parms, called from lookup_template_class.  */
      cat (expr_as_string (arg, 0));
    }
  {
    char *bufp = obstack_next_free (&scratch_obstack);
    int offset = 0;
    while (bufp[offset - 1] == ' ')
      offset--;
    obstack_blank_fast (&scratch_obstack, offset);

    /* B<C<char> >, not B<C<char>> */
    if (bufp[offset - 1] == '>')
      ccat (' ');
  }
  ccat ('>');
  ccat ('\0');
  return (char *) obstack_base (&scratch_obstack);

#if 0
 too_long:
#endif
  fatal ("out of (preallocated) string space creating template instantiation name");
  /* NOTREACHED */
  return NULL;
}

tree
classtype_mangled_name (t)
     tree t;
{
  if (CLASSTYPE_TEMPLATE_INFO (t)
      && PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (t)))
    {
      tree name = DECL_NAME (CLASSTYPE_TI_TEMPLATE (t));
      char *mangled_name = mangle_class_name_for_template
        (IDENTIFIER_POINTER (name),
         DECL_TEMPLATE_PARMS (CLASSTYPE_TI_TEMPLATE (t)),
         CLASSTYPE_TI_ARGS (t));
      tree id = get_identifier (mangled_name);
      IDENTIFIER_TEMPLATE (id) = name;
      return id;
    }
  else
    return TYPE_IDENTIFIER (t);
}

static void
add_pending_template (d)
     tree d;
{
  if (TREE_LANG_FLAG_0 (DECL_TEMPLATE_INFO (d)))
    return;

  *template_tail = perm_tree_cons
    (current_function_decl, d, NULL_TREE);
  template_tail = &TREE_CHAIN (*template_tail);
  TREE_LANG_FLAG_0 (DECL_TEMPLATE_INFO (d)) = 1;
}

/* Given an IDENTIFIER_NODE (type TEMPLATE_DECL) and a chain of
   parameters, find the desired type.

   D1 is the PTYPENAME terminal, and ARGLIST is the list of arguments.
   Since ARGLIST is build on the decl_obstack, we must copy it here
   to keep it from being reclaimed when the decl storage is reclaimed.

   IN_DECL, if non-NULL, is the template declaration we are trying to
   instantiate.  */
tree
lookup_template_class (d1, arglist, in_decl)
     tree d1, arglist;
     tree in_decl;
{
  tree template, parmlist;
  char *mangled_name;
  tree id, t;
  tree code_type_node;

  if (TREE_CODE (d1) == IDENTIFIER_NODE)
    {
      template = IDENTIFIER_GLOBAL_VALUE (d1); /* XXX */
      if (! template)
        template = IDENTIFIER_CLASS_VALUE (d1);
    }
  else if (TREE_CODE_CLASS (TREE_CODE (d1)) == 't' && IS_AGGR_TYPE (d1))
    {
      template = CLASSTYPE_TI_TEMPLATE (d1);
      d1 = DECL_NAME (template);
    }
  else
    my_friendly_abort (272);

  /* With something like `template <class T> class X class X { ... };'
     we could end up with D1 having nothing but an IDENTIFIER_LOCAL_VALUE.
     We don't want to do that, but we have to deal with the situation, so
     let's give them some syntax errors to chew on instead of a crash.  */
  if (! template)
    return error_mark_node;
  if (TREE_CODE (template) != TEMPLATE_DECL)
    {
      cp_error ("non-template type `%T' used as a template", d1);
      if (in_decl)
        cp_error_at ("for template declaration `%D'", in_decl);
      return error_mark_node;
    }

  if (PRIMARY_TEMPLATE_P (template))
    {
      parmlist = DECL_TEMPLATE_PARMS (template);

      arglist = coerce_template_parms (parmlist, arglist, template);
      if (arglist == error_mark_node)
        return error_mark_node;
      if (uses_template_parms (arglist))
        {
          tree found;
          if (comp_template_args
              (CLASSTYPE_TI_ARGS (TREE_TYPE (template)), arglist))
            found = TREE_TYPE (template);
          else
            {
              for (found = DECL_TEMPLATE_INSTANTIATIONS (template);
                   found; found = TREE_CHAIN (found))
                {
                  if (TI_USES_TEMPLATE_PARMS (found)
                      && comp_template_args (TREE_PURPOSE (found), arglist))
                    break;
                }
              if (found)
                found = TREE_VALUE (found);
            }

          if (found)
            {
              if (can_free (&permanent_obstack, arglist))
                obstack_free (&permanent_obstack, arglist);
              return found;
            }
        }

      mangled_name = mangle_class_name_for_template (IDENTIFIER_POINTER (d1),
                                                     parmlist, arglist);
      id = get_identifier (mangled_name);
      IDENTIFIER_TEMPLATE (id) = d1;

      maybe_push_to_top_level (uses_template_parms (arglist));
      t = xref_tag_from_type (TREE_TYPE (template), id, 1);
      pop_from_top_level ();
    }
  else
    {
      tree ctx = lookup_template_class (TYPE_CONTEXT (TREE_TYPE (template)),
                                        arglist, in_decl);
      id = d1;
      arglist = CLASSTYPE_TI_ARGS (ctx);

      if (TYPE_BEING_DEFINED (ctx) && ctx == current_class_type)
        {
          tree save_parms = current_template_parms;
          current_template_parms = NULL_TREE;
          t = xref_tag_from_type (TREE_TYPE (template), id, 0);
          current_template_parms = save_parms;
        }
      else
        {
          t = lookup_nested_type_by_name (ctx, id);
          my_friendly_assert (t != NULL_TREE, 42);
        }
    }

  /* Seems to be wanted. */
  CLASSTYPE_GOT_SEMICOLON (t) = 1;

  if (! CLASSTYPE_TEMPLATE_INFO (t))
    {
      arglist = copy_to_permanent (arglist);
      CLASSTYPE_TEMPLATE_INFO (t)
        = perm_tree_cons (template, arglist, NULL_TREE);
      DECL_TEMPLATE_INSTANTIATIONS (template) = perm_tree_cons
        (arglist, t, DECL_TEMPLATE_INSTANTIATIONS (template));
      TI_USES_TEMPLATE_PARMS (DECL_TEMPLATE_INSTANTIATIONS (template))
        = uses_template_parms (arglist);

      SET_CLASSTYPE_IMPLICIT_INSTANTIATION (t);

      /* We need to set this again after CLASSTYPE_TEMPLATE_INFO is set up. */
      DECL_ASSEMBLER_NAME (TYPE_MAIN_DECL (t)) = id;
      if (! uses_template_parms (arglist))
        DECL_ASSEMBLER_NAME (TYPE_MAIN_DECL (t)) 
          = get_identifier (build_overload_name (t, 1, 1));

      if (flag_external_templates && ! uses_template_parms (arglist)
          && CLASSTYPE_INTERFACE_KNOWN (TREE_TYPE (template))
          && ! CLASSTYPE_INTERFACE_ONLY (TREE_TYPE (template)))
        {
          tree d;

          instantiate_class_template (t);

          for (d = TYPE_METHODS (t); d; d = TREE_CHAIN (d))
            add_pending_template (d);
        }
    }

  return t;
}
\f
/* Should be defined in parse.h.  */
extern int yychar;

int
uses_template_parms (t)
     tree t;
{
  if (!t)
    return 0;
  switch (TREE_CODE (t))
    {
    case INDIRECT_REF:
    case COMPONENT_REF:
      /* We assume that the object must be instantiated in order to build
         the COMPONENT_REF, so we test only whether the type of the
         COMPONENT_REF uses template parms.  */
      return uses_template_parms (TREE_TYPE (t));

    case IDENTIFIER_NODE:
      if (!IDENTIFIER_TEMPLATE (t))
        return 0;
      my_friendly_abort (42);

      /* aggregates of tree nodes */
    case TREE_VEC:
      {
        int i = TREE_VEC_LENGTH (t);
        while (i--)
          if (uses_template_parms (TREE_VEC_ELT (t, i)))
            return 1;
        return 0;
      }
    case TREE_LIST:
      if (uses_template_parms (TREE_PURPOSE (t))
          || uses_template_parms (TREE_VALUE (t)))
        return 1;
      return uses_template_parms (TREE_CHAIN (t));

      /* constructed type nodes */
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      return uses_template_parms (TREE_TYPE (t));
    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_FLAG (t))
        return uses_template_parms (TYPE_PTRMEMFUNC_FN_TYPE (t));
    case UNION_TYPE:
      if (! CLASSTYPE_TEMPLATE_INFO (t))
        return 0;
      return uses_template_parms (TREE_VALUE (CLASSTYPE_TEMPLATE_INFO (t)));
    case FUNCTION_TYPE:
      if (uses_template_parms (TYPE_ARG_TYPES (t)))
        return 1;
      return uses_template_parms (TREE_TYPE (t));
    case ARRAY_TYPE:
      if (uses_template_parms (TYPE_DOMAIN (t)))
        return 1;
      return uses_template_parms (TREE_TYPE (t));
    case OFFSET_TYPE:
      if (uses_template_parms (TYPE_OFFSET_BASETYPE (t)))
        return 1;
      return uses_template_parms (TREE_TYPE (t));
    case METHOD_TYPE:
      if (uses_template_parms (TYPE_METHOD_BASETYPE (t)))
        return 1;
      if (uses_template_parms (TYPE_ARG_TYPES (t)))
        return 1;
      return uses_template_parms (TREE_TYPE (t));

      /* decl nodes */
    case TYPE_DECL:
      return uses_template_parms (TREE_TYPE (t));

    case FUNCTION_DECL:
    case VAR_DECL:
      /* ??? What about FIELD_DECLs?  */
      if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t)
          && uses_template_parms (DECL_TI_ARGS (t)))
        return 1;
      /* fall through */
    case CONST_DECL:
    case PARM_DECL:
      if (uses_template_parms (TREE_TYPE (t)))
        return 1;
      if (DECL_CONTEXT (t) && uses_template_parms (DECL_CONTEXT (t)))
        return 1;
      return 0;

    case CALL_EXPR:
      return uses_template_parms (TREE_TYPE (t));
    case ADDR_EXPR:
      return uses_template_parms (TREE_OPERAND (t, 0));

      /* template parm nodes */
    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_CONST_PARM:
      return 1;

      /* simple type nodes */
    case INTEGER_TYPE:
      if (uses_template_parms (TYPE_MIN_VALUE (t)))
        return 1;
      return uses_template_parms (TYPE_MAX_VALUE (t));

    case REAL_TYPE:
    case VOID_TYPE:
    case ENUMERAL_TYPE:
    case BOOLEAN_TYPE:
      return 0;

      /* constants */
    case INTEGER_CST:
    case REAL_CST:
    case STRING_CST:
      return 0;

    case ERROR_MARK:
      /* Non-error_mark_node ERROR_MARKs are bad things.  */
      my_friendly_assert (t == error_mark_node, 274);
      /* NOTREACHED */
      return 0;

    case LOOKUP_EXPR:
    case TYPENAME_TYPE:
      return 1;

    case CONSTRUCTOR:
      if (TREE_TYPE (t) && TYPE_PTRMEMFUNC_P (TREE_TYPE (t)))
        return uses_template_parms (TYPE_PTRMEMFUNC_FN_TYPE (TREE_TYPE (t)));
      /* else fall through */

    default:
      switch (TREE_CODE_CLASS (TREE_CODE (t)))
        {
        case '1':
        case '2':
        case 'e':
        case '<':
          {
            int i;
            for (i = tree_code_length[(int) TREE_CODE (t)]; --i >= 0;)
              if (uses_template_parms (TREE_OPERAND (t, i)))
                return 1;
            return 0;
          }
        default:
          break;
        }
      sorry ("testing %s for template parms",
             tree_code_name [(int) TREE_CODE (t)]);
      my_friendly_abort (82);
      /* NOTREACHED */
      return 0;
    }
}

static struct tinst_level *current_tinst_level = 0;
static struct tinst_level *free_tinst_level = 0;
static int tinst_depth = 0;
int max_tinst_depth = 17;
#ifdef GATHER_STATISTICS
int depth_reached = 0;
#endif

int
push_tinst_level (d)
     tree d;
{
  struct tinst_level *new;

  if (tinst_depth >= max_tinst_depth)
    {
      struct tinst_level *p = current_tinst_level;
      int line = lineno;
      char *file = input_filename;

      error ("template instantiation depth exceeds maximum of %d",
             max_tinst_depth);
      cp_error ("  instantiating `%D'", d);

      for (; p; p = p->next)
        {
          cp_error ("  instantiated from `%D'", p->decl);
          lineno = p->line;
          input_filename = p->file;
        }
      error ("  instantiated from here");

      lineno = line;
      input_filename = file;

      return 0;
    }

  if (free_tinst_level)
    {
      new = free_tinst_level;
      free_tinst_level = new->next;
    }
  else
    new = (struct tinst_level *) xmalloc (sizeof (struct tinst_level));

  new->decl = d;
  new->line = lineno;
  new->file = input_filename;
  new->next = current_tinst_level;
  current_tinst_level = new;

  ++tinst_depth;
#ifdef GATHER_STATISTICS
  if (tinst_depth > depth_reached)
    depth_reached = tinst_depth;
#endif

  return 1;
}

void
pop_tinst_level ()
{
  struct tinst_level *old = current_tinst_level;

  current_tinst_level = old->next;
  old->next = free_tinst_level;
  free_tinst_level = old;
  --tinst_depth;
}

struct tinst_level *
tinst_for_decl ()
{
  struct tinst_level *p = current_tinst_level;

  if (p)
    for (; p->next ; p = p->next )
      ;
  return p;
}

tree
instantiate_class_template (type)
     tree type;
{
  tree template, template_info, args, pattern, t, *field_chain;

  if (type == error_mark_node)
    return error_mark_node;

  template_info = CLASSTYPE_TEMPLATE_INFO (type);

  if (TYPE_BEING_DEFINED (type) || TYPE_SIZE (type))
    return type;

  template = TI_TEMPLATE (template_info);
  my_friendly_assert (TREE_CODE (template) == TEMPLATE_DECL, 279);
  args = TI_ARGS (template_info);
  pattern = TREE_TYPE (template);

  if (TYPE_SIZE (pattern) == NULL_TREE)
    return type;

  TYPE_BEING_DEFINED (type) = 1;

  if (! push_tinst_level (type))
    return type;

  maybe_push_to_top_level (uses_template_parms (type));
  pushclass (type, 0);

  if (flag_external_templates)
    {
      if (flag_alt_external_templates)
        {
          CLASSTYPE_INTERFACE_ONLY (type) = interface_only;
          SET_CLASSTYPE_INTERFACE_UNKNOWN_X (type, interface_unknown);
          CLASSTYPE_VTABLE_NEEDS_WRITING (type)
            = ! CLASSTYPE_INTERFACE_ONLY (type)
              && CLASSTYPE_INTERFACE_KNOWN (type);
        }
      else
        {
          CLASSTYPE_INTERFACE_ONLY (type) = CLASSTYPE_INTERFACE_ONLY (pattern);
          SET_CLASSTYPE_INTERFACE_UNKNOWN_X
            (type, CLASSTYPE_INTERFACE_UNKNOWN (pattern));
          CLASSTYPE_VTABLE_NEEDS_WRITING (type)
            = ! CLASSTYPE_INTERFACE_ONLY (type)
              && CLASSTYPE_INTERFACE_KNOWN (type);
        }
    }
  else
    {
      SET_CLASSTYPE_INTERFACE_UNKNOWN (type);
      CLASSTYPE_VTABLE_NEEDS_WRITING (type) = 1;
    }

  {
    tree binfo = TYPE_BINFO (type);
    tree pbases = TYPE_BINFO_BASETYPES (pattern);

    if (pbases)
      {
        tree bases;
        int i;
        int len = TREE_VEC_LENGTH (pbases);
        BINFO_BASETYPES (binfo) = bases = make_tree_vec (len);
        for (i = 0; i < len; ++i)
          {
            tree elt;

            TREE_VEC_ELT (bases, i) = elt
              = tsubst (TREE_VEC_ELT (pbases, i), &TREE_VEC_ELT (args, 0),
                        TREE_VEC_LENGTH (args), NULL_TREE);
            BINFO_INHERITANCE_CHAIN (elt) = binfo;

            if (! uses_template_parms (type) &&
                TYPE_SIZE (complete_type (TREE_TYPE (elt))) == NULL_TREE)
              cp_error ("base class `%T' of `%T' has incomplete type",
                        TREE_TYPE (elt), type);
          }
      }
  }

  CLASSTYPE_LOCAL_TYPEDECLS (type) = CLASSTYPE_LOCAL_TYPEDECLS (pattern);

  field_chain = &TYPE_FIELDS (type);

  for (t = CLASSTYPE_TAGS (pattern); t; t = TREE_CHAIN (t))
    {
      tree name = TREE_PURPOSE (t);
      tree tag = TREE_VALUE (t);
      tree newtag;

      /* These will add themselves to CLASSTYPE_TAGS for the new type.  */
      if (TREE_CODE (tag) == ENUMERAL_TYPE)
        newtag = start_enum (name);
      else
        newtag = tsubst (tag, &TREE_VEC_ELT (args, 0),
                         TREE_VEC_LENGTH (args), NULL_TREE);

      if (TREE_CODE (tag) == ENUMERAL_TYPE)
        {
          tree e, values = NULL_TREE, *last = &values;

          for (e = TYPE_VALUES (tag); e; e = TREE_CHAIN (e))
            {
              tree elt = build_enumerator
                (TREE_PURPOSE (e),
                 tsubst_expr (TREE_VALUE (e), &TREE_VEC_ELT (args, 0),
                              TREE_VEC_LENGTH (args), NULL_TREE));
              DECL_FIELD_CONTEXT (TREE_VALUE (elt)) = type;
              *last = elt;
              last = &TREE_CHAIN (elt);
            }

          finish_enum (newtag, values);

          *field_chain = grok_enum_decls (newtag, NULL_TREE);
          while (*field_chain)
            field_chain = &TREE_CHAIN (*field_chain);
        }
    }

  /* Don't replace enum constants here.  */
  for (t = TYPE_FIELDS (pattern); t; t = TREE_CHAIN (t))
    if (TREE_CODE (t) != CONST_DECL)
      {
        tree r = tsubst (t, &TREE_VEC_ELT (args, 0),
                         TREE_VEC_LENGTH (args), NULL_TREE);
        if (TREE_CODE (r) == VAR_DECL)
          {
            if (! uses_template_parms (r))
              pending_statics = perm_tree_cons (NULL_TREE, r, pending_statics);
            /* Perhaps I should do more of grokfield here. */
            start_decl_1 (r);
            DECL_IN_AGGR_P (r) = 1;
            DECL_EXTERNAL (r) = 1;
            cp_finish_decl (r, DECL_INITIAL (r), NULL_TREE, 0, 0);
          }

        *field_chain = r;
        field_chain = &TREE_CHAIN (r);
      }

  TYPE_METHODS (type) = tsubst_chain (TYPE_METHODS (pattern), args);

  DECL_FRIENDLIST (TYPE_MAIN_DECL (type))
    = tsubst (DECL_FRIENDLIST (TYPE_MAIN_DECL (pattern)),
              &TREE_VEC_ELT (args, 0), TREE_VEC_LENGTH (args), NULL_TREE);

  {
    tree d = CLASSTYPE_FRIEND_CLASSES (type) =
      tsubst (CLASSTYPE_FRIEND_CLASSES (pattern), &TREE_VEC_ELT (args, 0),
              TREE_VEC_LENGTH (args), NULL_TREE);

    /* This does injection for friend classes.  */
    for (; d; d = TREE_CHAIN (d))
      TREE_VALUE (d) = xref_tag_from_type (TREE_VALUE (d), NULL_TREE, 1);

    d = tsubst (DECL_TEMPLATE_INJECT (template), &TREE_VEC_ELT (args, 0),
                     TREE_VEC_LENGTH (args), NULL_TREE);

    for (; d; d = TREE_CHAIN (d))
      {
        tree t = TREE_VALUE (d);

        if (TREE_CODE (t) == TYPE_DECL)
          /* Already injected.  */;
        else
          pushdecl (t);
      }
  }

  TYPE_HAS_CONSTRUCTOR (type) = TYPE_HAS_CONSTRUCTOR (pattern);
  TYPE_HAS_DESTRUCTOR (type) = TYPE_HAS_DESTRUCTOR (pattern);
  TYPE_HAS_ASSIGNMENT (type) = TYPE_HAS_ASSIGNMENT (pattern);
  TYPE_OVERLOADS_CALL_EXPR (type) = TYPE_OVERLOADS_CALL_EXPR (pattern);
  TYPE_OVERLOADS_ARRAY_REF (type) = TYPE_OVERLOADS_ARRAY_REF (pattern);
  TYPE_OVERLOADS_ARROW (type) = TYPE_OVERLOADS_ARROW (pattern);
  TYPE_GETS_NEW (type) = TYPE_GETS_NEW (pattern);
  TYPE_GETS_DELETE (type) = TYPE_GETS_DELETE (pattern);
  TYPE_VEC_DELETE_TAKES_SIZE (type) = TYPE_VEC_DELETE_TAKES_SIZE (pattern);
  TYPE_HAS_ASSIGN_REF (type) = TYPE_HAS_ASSIGN_REF (pattern);
  TYPE_HAS_CONST_ASSIGN_REF (type) = TYPE_HAS_CONST_ASSIGN_REF (pattern);
  TYPE_HAS_ABSTRACT_ASSIGN_REF (type) = TYPE_HAS_ABSTRACT_ASSIGN_REF (pattern);
  TYPE_HAS_INIT_REF (type) = TYPE_HAS_INIT_REF (pattern);
  TYPE_HAS_CONST_INIT_REF (type) = TYPE_HAS_CONST_INIT_REF (pattern);
  TYPE_GETS_INIT_AGGR (type) = TYPE_GETS_INIT_AGGR (pattern);
  TYPE_HAS_DEFAULT_CONSTRUCTOR (type) = TYPE_HAS_DEFAULT_CONSTRUCTOR (pattern);
  TYPE_HAS_CONVERSION (type) = TYPE_HAS_CONVERSION (pattern);
  TYPE_USES_COMPLEX_INHERITANCE (type)
    = TYPE_USES_COMPLEX_INHERITANCE (pattern);
  TYPE_USES_VIRTUAL_BASECLASSES (type)
    = TYPE_USES_VIRTUAL_BASECLASSES (pattern);

  if (! uses_template_parms (type))
    {
      tree tmp;
      for (tmp = TYPE_FIELDS (type); tmp; tmp = TREE_CHAIN (tmp))
        if (TREE_CODE (tmp) == FIELD_DECL
            && TREE_CODE (DECL_NAME (tmp)) != SCOPE_REF)
          require_complete_type (tmp);

      /* XXX handle attributes */
      type = finish_struct_1 (type, 0, 0);
    }
  else
    {
      TYPE_SIZE (type) = integer_zero_node;
      CLASSTYPE_METHOD_VEC (type)
        = finish_struct_methods (type, TYPE_METHODS (type), 1);
    }

  TYPE_BEING_DEFINED (type) = 0;
  popclass (0);

  pop_from_top_level ();
  pop_tinst_level ();

  return type;
}

static int
list_eq (t1, t2)
     tree t1, t2;
{
  if (t1 == NULL_TREE)
    return t2 == NULL_TREE;
  if (t2 == NULL_TREE)
    return 0;
  /* Don't care if one declares its arg const and the other doesn't -- the
     main variant of the arg type is all that matters.  */
  if (TYPE_MAIN_VARIANT (TREE_VALUE (t1))
      != TYPE_MAIN_VARIANT (TREE_VALUE (t2)))
    return 0;
  return list_eq (TREE_CHAIN (t1), TREE_CHAIN (t2));
}

tree 
lookup_nested_type_by_name (ctype, name)
        tree ctype, name;
{
  tree t;

  complete_type (ctype);

  for (t = CLASSTYPE_TAGS (ctype); t; t = TREE_CHAIN (t))
    {
      if (name == TREE_PURPOSE (t))
        return TREE_VALUE (t);
    }
  return NULL_TREE;
}

tree
tsubst (t, args, nargs, in_decl)
     tree t, *args;
     int nargs;
     tree in_decl;
{
  tree type;

  if (t == NULL_TREE || t == error_mark_node
      || t == integer_type_node
      || t == void_type_node
      || t == char_type_node)
    return t;

  type = TREE_TYPE (t);
  if (type == unknown_type_node)
    my_friendly_abort (42);
  if (type && TREE_CODE (t) != FUNCTION_DECL)
    type = tsubst (type, args, nargs, in_decl);

  switch (TREE_CODE (t))
    {
    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_P (t))
        {
          tree r = build_ptrmemfunc_type
            (tsubst (TYPE_PTRMEMFUNC_FN_TYPE (t), args, nargs, in_decl));
          return cp_build_type_variant (r, TYPE_READONLY (t),
                                        TYPE_VOLATILE (t));
        }

      /* else fall through */
    case UNION_TYPE:
      if (uses_template_parms (t))
        {
          tree argvec = tsubst (CLASSTYPE_TI_ARGS (t), args, nargs, in_decl);
          tree r = lookup_template_class (t, argvec, in_decl);
          return cp_build_type_variant (r, TYPE_READONLY (t),
                                        TYPE_VOLATILE (t));
        }

      /* else fall through */
    case ERROR_MARK:
    case IDENTIFIER_NODE:
    case OP_IDENTIFIER:
    case VOID_TYPE:
    case REAL_TYPE:
    case BOOLEAN_TYPE:
    case INTEGER_CST:
    case REAL_CST:
    case STRING_CST:
      return t;

    case ENUMERAL_TYPE:
      {
        tree ctx = tsubst (TYPE_CONTEXT (t), args, nargs, in_decl);
        if (ctx == NULL_TREE)
          return t;
        else
          return lookup_nested_type_by_name (ctx, TYPE_IDENTIFIER (t));
      }

    case INTEGER_TYPE:
      if (t == integer_type_node)
        return t;

      if (TREE_CODE (TYPE_MIN_VALUE (t)) == INTEGER_CST
          && TREE_CODE (TYPE_MAX_VALUE (t)) == INTEGER_CST)
        return t;

      {
        tree max = tsubst_expr (TYPE_MAX_VALUE (t), args, nargs, in_decl);
        if (current_template_parms)
          {
            tree itype = make_node (INTEGER_TYPE);
            TYPE_MIN_VALUE (itype) = size_zero_node;
            TYPE_MAX_VALUE (itype) = max;
            return itype;
          }
        return build_index_2_type (size_zero_node, max);
      }

    case TEMPLATE_TYPE_PARM:
      {
        tree arg = args[TEMPLATE_TYPE_IDX (t)];
        return cp_build_type_variant
          (arg, TYPE_READONLY (arg) || TYPE_READONLY (t),
           TYPE_VOLATILE (arg) || TYPE_VOLATILE (t));
      }

    case TEMPLATE_CONST_PARM:
      return args[TEMPLATE_CONST_IDX (t)];

    case FUNCTION_DECL:
      {
        tree r = NULL_TREE;
        tree arg_types, ctx;

        int member;

        if (DECL_CONTEXT (t) != NULL_TREE
            && TREE_CODE_CLASS (TREE_CODE (DECL_CONTEXT (t))) == 't')
          {
            if (DECL_NAME (t) == constructor_name (DECL_CONTEXT (t)))
              member = 2;
            else
              member = 1;
            ctx = tsubst (DECL_CLASS_CONTEXT (t), args, nargs, t);
            type = tsubst (type, args, nargs, in_decl);
          }
        else
          {
            member = 0;
            ctx = NULL_TREE;
            type = tsubst (type, args, nargs, in_decl);
          }

        if (type == TREE_TYPE (t)
            && (! member || ctx == DECL_CLASS_CONTEXT (t)))
          return t;

        /* Do we already have this instantiation?  */
        if (DECL_TEMPLATE_INFO (t) != NULL_TREE)
          {
            tree tmpl = TREE_PURPOSE (DECL_TEMPLATE_INFO (t));
            tree decls = DECL_TEMPLATE_INSTANTIATIONS (tmpl);

            for (; decls; decls = TREE_CHAIN (decls))
              if (TREE_TYPE (TREE_VALUE (decls)) == type
                  && DECL_CLASS_CONTEXT (TREE_VALUE (decls)) == ctx)
                return TREE_VALUE (decls);
          }

        /* We do NOT check for matching decls pushed separately at this
           point, as they may not represent instantiations of this
           template, and in any case are considered separate under the
           discrete model.  */

        r = copy_node (t);
        copy_lang_decl (r);
        TREE_TYPE (r) = type;

        DECL_CONTEXT (r)
          = tsubst (DECL_CONTEXT (t), args, nargs, t);
        DECL_CLASS_CONTEXT (r) = ctx;

        if (member && !strncmp (OPERATOR_TYPENAME_FORMAT,
                                IDENTIFIER_POINTER (DECL_NAME (r)),
                                sizeof (OPERATOR_TYPENAME_FORMAT) - 1))
          {
            /* Type-conversion operator.  Reconstruct the name, in
               case it's the name of one of the template's parameters.  */
            DECL_NAME (r) = build_typename_overload (TREE_TYPE (type));
          }

        arg_types = TYPE_VALUES (type);

        if (member && TREE_CODE (type) == FUNCTION_TYPE)
          arg_types = hash_tree_chain
            (build_pointer_type (DECL_CONTEXT (r)), arg_types);

        if (DESTRUCTOR_NAME_P (DECL_ASSEMBLER_NAME (t)))
          {
            char *buf, *dbuf = build_overload_name (ctx, 1, 1);
            int len = sizeof (DESTRUCTOR_DECL_PREFIX) - 1;
            buf = (char *) alloca (strlen (dbuf)
                                   + sizeof (DESTRUCTOR_DECL_PREFIX));
            bcopy (DESTRUCTOR_DECL_PREFIX, buf, len);
            buf[len] = '\0';
            strcat (buf, dbuf);
            DECL_ASSEMBLER_NAME (r) = get_identifier (buf);
          }
        else
          DECL_ASSEMBLER_NAME (r)
            = build_decl_overload (DECL_NAME (r), arg_types, member);
        DECL_RTL (r) = 0;
        make_decl_rtl (r, NULL_PTR, 1);

        DECL_ARGUMENTS (r) = tsubst (DECL_ARGUMENTS (t), args, nargs, t);
        DECL_MAIN_VARIANT (r) = r;
        DECL_RESULT (r) = NULL_TREE;
        DECL_INITIAL (r) = NULL_TREE;

        TREE_STATIC (r) = 0;
        TREE_PUBLIC (r) = 1;
        DECL_EXTERNAL (r) = 1;
        DECL_INTERFACE_KNOWN (r) = 0;
        DECL_DEFER_OUTPUT (r) = 0;
        TREE_CHAIN (r) = NULL_TREE;
        DECL_CHAIN (r) = NULL_TREE;

        if (IDENTIFIER_OPNAME_P (DECL_NAME (r)))
          grok_op_properties (r, DECL_VIRTUAL_P (r), DECL_FRIEND_P (r));

        /* Look for matching decls for the moment.  */
        if (! member)
          {
            tree decls = lookup_name_nonclass (DECL_NAME (t));
            tree d = NULL_TREE;
    
            if (decls == NULL_TREE)
              /* no match */;
            else if (is_overloaded_fn (decls))
              for (decls = get_first_fn (decls); decls;
                   decls = DECL_CHAIN (decls))
                {
                  if (TREE_CODE (decls) == FUNCTION_DECL
                      && TREE_TYPE (decls) == type)
                    {
                      d = decls;
                      break;
                    }
                }

            if (d)
              {
                int dcl_only = ! DECL_INITIAL (d);
                if (dcl_only)
                  DECL_INITIAL (r) = error_mark_node;
                duplicate_decls (r, d);
                r = d;
                if (dcl_only)
                  DECL_INITIAL (r) = 0;
              }
          }

        if (DECL_TEMPLATE_INFO (t) != NULL_TREE)
          {
            tree tmpl = DECL_TI_TEMPLATE (t);
            tree *declsp = &DECL_TEMPLATE_INSTANTIATIONS (tmpl);
            tree argvec = tsubst (TREE_VALUE (DECL_TEMPLATE_INFO (t)),
                                  args, nargs, in_decl);

            DECL_TEMPLATE_INFO (r) = perm_tree_cons (tmpl, argvec, NULL_TREE);
            *declsp = perm_tree_cons (argvec, r, *declsp);

            /* If we have a preexisting version of this function, don't expand
               the template version, use the other instead.  */
            if (TREE_STATIC (r) || DECL_TEMPLATE_SPECIALIZATION (r))
              SET_DECL_TEMPLATE_SPECIALIZATION (r);
            else
              SET_DECL_IMPLICIT_INSTANTIATION (r);

            DECL_TEMPLATE_INSTANTIATIONS (tmpl) =
              tree_cons (argvec, r, DECL_TEMPLATE_INSTANTIATIONS (tmpl));
          }

        return r;
      }

    case PARM_DECL:
      {
        tree r = copy_node (t);
        TREE_TYPE (r) = type;
        DECL_INITIAL (r) = TREE_TYPE (r);
        DECL_CONTEXT (r) = NULL_TREE;
#ifdef PROMOTE_PROTOTYPES
        if ((TREE_CODE (type) == INTEGER_TYPE
             || TREE_CODE (type) == ENUMERAL_TYPE)
            && TYPE_PRECISION (type) < TYPE_PRECISION (integer_type_node))
          DECL_ARG_TYPE (r) = integer_type_node;
#endif
        if (TREE_CHAIN (t))
          TREE_CHAIN (r) = tsubst (TREE_CHAIN (t), args, nargs, TREE_CHAIN (t));
        return r;
      }

    case FIELD_DECL:
      {
        tree r = copy_node (t);
        TREE_TYPE (r) = type;
        copy_lang_decl (r);
#if 0
        DECL_FIELD_CONTEXT (r) = tsubst (DECL_FIELD_CONTEXT (t), args, nargs, in_decl);
#endif
        DECL_INITIAL (r) = tsubst_expr (DECL_INITIAL (t), args, nargs, in_decl);
        TREE_CHAIN (r) = NULL_TREE;
        return r;
      }

    case USING_DECL:
      {
        tree r = copy_node (t);
        DECL_INITIAL (r)
          = tsubst_copy (DECL_INITIAL (t), args, nargs, in_decl);
        TREE_CHAIN (r) = NULL_TREE;
        return r;
      }

    case VAR_DECL:
      {
        tree r;
        tree ctx = tsubst_copy (DECL_CONTEXT (t), args, nargs, in_decl);

        /* Do we already have this instantiation?  */
        if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t))
          {
            tree tmpl = DECL_TI_TEMPLATE (t);
            tree decls = DECL_TEMPLATE_INSTANTIATIONS (tmpl);

            for (; decls; decls = TREE_CHAIN (decls))
              if (DECL_CONTEXT (TREE_VALUE (decls)) == ctx)
                return TREE_VALUE (decls);
          }

        r = copy_node (t);
        TREE_TYPE (r) = type;
        DECL_CONTEXT (r) = ctx;
        if (TREE_STATIC (r))
          DECL_ASSEMBLER_NAME (r)
            = build_static_name (DECL_CONTEXT (r), DECL_NAME (r));
        DECL_INITIAL (r) = tsubst_expr
          (DECL_INITIAL (t), args, nargs, in_decl);

        DECL_RTL (r) = 0;
        DECL_SIZE (r) = 0;

        if (DECL_LANG_SPECIFIC (r))
          {
            copy_lang_decl (r);
            DECL_CLASS_CONTEXT (r) = DECL_CONTEXT (r);
          }

        if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t))
          {
            tree tmpl = DECL_TI_TEMPLATE (t);
            tree *declsp = &DECL_TEMPLATE_INSTANTIATIONS (tmpl);
            tree argvec = tsubst (TREE_VALUE (DECL_TEMPLATE_INFO (t)),
                                  args, nargs, in_decl);

            DECL_TEMPLATE_INFO (r) = perm_tree_cons (tmpl, argvec, NULL_TREE);
            *declsp = perm_tree_cons (argvec, r, *declsp);
            SET_DECL_IMPLICIT_INSTANTIATION (r);
          }
        TREE_CHAIN (r) = NULL_TREE;
        return r;
      }

    case TYPE_DECL:
      {
        tree r = copy_node (t);
        TREE_TYPE (r) = type;
        set_nested_typename (r, current_class_name, DECL_NAME (r), type);
        TREE_CHAIN (r) = NULL_TREE;
        return r;
      }   

    case TREE_LIST:
      {
        tree purpose, value, chain, result;
        int via_public, via_virtual, via_protected;

        if (t == void_list_node)
          return t;

        via_public = TREE_VIA_PUBLIC (t);
        via_protected = TREE_VIA_PROTECTED (t);
        via_virtual = TREE_VIA_VIRTUAL (t);

        purpose = TREE_PURPOSE (t);
        if (purpose)
          purpose = tsubst (purpose, args, nargs, in_decl);
        value = TREE_VALUE (t);
        if (value)
          value = tsubst (value, args, nargs, in_decl);
        chain = TREE_CHAIN (t);
        if (chain && chain != void_type_node)
          chain = tsubst (chain, args, nargs, in_decl);
        if (purpose == TREE_PURPOSE (t)
            && value == TREE_VALUE (t)
            && chain == TREE_CHAIN (t))
          return t;
        result = hash_tree_cons (via_public, via_virtual, via_protected,
                                 purpose, value, chain);
        TREE_PARMLIST (result) = TREE_PARMLIST (t);
        return result;
      }
    case TREE_VEC:
      if (type != NULL_TREE)
        {
          t = copy_node (t);

          if (type == TREE_TYPE (t))
            return t;

          TREE_TYPE (t) = complete_type (type);
          BINFO_VTABLE (t) = TYPE_BINFO_VTABLE (type);
          BINFO_VIRTUALS (t) = TYPE_BINFO_VIRTUALS (type);
          if (TYPE_BINFO_BASETYPES (type) != NULL_TREE)
            BINFO_BASETYPES (t) = copy_node (TYPE_BINFO_BASETYPES (type));

          return t;
        }
      {
        int len = TREE_VEC_LENGTH (t), need_new = 0, i;
        tree *elts = (tree *) alloca (len * sizeof (tree));

        bzero ((char *) elts, len * sizeof (tree));

        for (i = 0; i < len; i++)
          {
            elts[i] = tsubst_expr (TREE_VEC_ELT (t, i), args, nargs, in_decl);
            if (elts[i] != TREE_VEC_ELT (t, i))
              need_new = 1;
          }

        if (!need_new)
          return t;

        t = make_tree_vec (len);
        for (i = 0; i < len; i++)
          TREE_VEC_ELT (t, i) = elts[i];
        
        return t;
      }
    case POINTER_TYPE:
    case REFERENCE_TYPE:
      {
        tree r;
        enum tree_code code;
        if (type == TREE_TYPE (t))
          return t;

        code = TREE_CODE (t);
        if (code == POINTER_TYPE)
          r = build_pointer_type (type);
        else
          r = build_reference_type (type);
        r = cp_build_type_variant (r, TYPE_READONLY (t), TYPE_VOLATILE (t));
        /* Will this ever be needed for TYPE_..._TO values?  */
        layout_type (r);
        return r;
      }
    case OFFSET_TYPE:
      return build_offset_type
        (tsubst (TYPE_OFFSET_BASETYPE (t), args, nargs, in_decl), type);
    case FUNCTION_TYPE:
    case METHOD_TYPE:
      {
        tree values = TYPE_ARG_TYPES (t);
        tree context = TYPE_CONTEXT (t);
        tree new_value;

        /* Don't bother recursing if we know it won't change anything.  */
        if (values != void_list_node)
          {
            /* This should probably be rewritten to use hash_tree_cons for
               the memory savings.  */
            tree first = NULL_TREE;
            tree last;

            for (; values && values != void_list_node;
                 values = TREE_CHAIN (values))
              {
                tree value
                  = tsubst (TREE_VALUE (values), args, nargs, in_decl);
                tree purpose = tsubst_expr (TREE_PURPOSE (values),
                                       args, nargs, in_decl);
                tree x = build_tree_list (purpose, value);

                if (first)
                  TREE_CHAIN (last) = x;
                else
                  first = x;
                last = x;
              }

            if (values == void_list_node)
              TREE_CHAIN (last) = void_list_node;

            values = first;
          }
        if (context)
          context = tsubst (context, args, nargs, in_decl);
        /* Could also optimize cases where return value and
           values have common elements (e.g., T min(const &T, const T&).  */

        /* If the above parameters haven't changed, just return the type.  */
        if (type == TREE_TYPE (t)
            && values == TYPE_VALUES (t)
            && context == TYPE_CONTEXT (t))
          return t;

        /* Construct a new type node and return it.  */
        if (TREE_CODE (t) == FUNCTION_TYPE
            && context == NULL_TREE)
          {
            new_value = build_function_type (type, values);
          }
        else if (context == NULL_TREE)
          {
            tree base = tsubst (TREE_TYPE (TREE_VALUE (TYPE_ARG_TYPES (t))),
                                args, nargs, in_decl);
            new_value = build_cplus_method_type (base, type,
                                                 TREE_CHAIN (values));
          }
        else
          {
            new_value = make_node (TREE_CODE (t));
            TREE_TYPE (new_value) = type;
            TYPE_CONTEXT (new_value) = context;
            TYPE_VALUES (new_value) = values;
            TYPE_SIZE (new_value) = TYPE_SIZE (t);
            TYPE_ALIGN (new_value) = TYPE_ALIGN (t);
            TYPE_MODE (new_value) = TYPE_MODE (t);
            if (TYPE_METHOD_BASETYPE (t))
              TYPE_METHOD_BASETYPE (new_value) = tsubst (TYPE_METHOD_BASETYPE (t),
                                                         args, nargs, in_decl);
            /* Need to generate hash value.  */
            my_friendly_abort (84);
          }
        new_value = build_type_variant (new_value,
                                        TYPE_READONLY (t),
                                        TYPE_VOLATILE (t));
        return new_value;
      }
    case ARRAY_TYPE:
      {
        tree domain = tsubst (TYPE_DOMAIN (t), args, nargs, in_decl);
        tree r;
        if (type == TREE_TYPE (t) && domain == TYPE_DOMAIN (t))
          return t;
        r = build_cplus_array_type (type, domain);
        return r;
      }

    case PLUS_EXPR:
    case MINUS_EXPR:
      return fold (build (TREE_CODE (t), TREE_TYPE (t),
                          tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
                          tsubst (TREE_OPERAND (t, 1), args, nargs, in_decl)));

    case NEGATE_EXPR:
    case NOP_EXPR:
      return fold (build1 (TREE_CODE (t), TREE_TYPE (t),
                           tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl)));

    case TYPENAME_TYPE:
      {
        tree ctx = tsubst (TYPE_CONTEXT (t), args, nargs, in_decl);
        tree f = make_typename_type (ctx, TYPE_IDENTIFIER (t));
        return cp_build_type_variant
          (f, TYPE_READONLY (f) || TYPE_READONLY (t),
           TYPE_VOLATILE (f) || TYPE_VOLATILE (t));
      }

    case INDIRECT_REF:
      return make_pointer_declarator
        (type, tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl));
      
    case ADDR_EXPR:
      return make_reference_declarator
        (type, tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl));

    case ARRAY_REF:
      return build_parse_node
        (ARRAY_REF, tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl));

    case CALL_EXPR:
      return build_parse_node
        (CALL_EXPR, tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst (TREE_OPERAND (t, 1), args, nargs, in_decl), 0);

    case SCOPE_REF:
      return build_parse_node
        (TREE_CODE (t), tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst (TREE_OPERAND (t, 1), args, nargs, in_decl));

    default:
      sorry ("use of `%s' in template",
             tree_code_name [(int) TREE_CODE (t)]);
      return error_mark_node;
    }
}

void
do_pushlevel ()
{
  emit_line_note (input_filename, lineno);
  pushlevel (0);
  clear_last_expr ();
  push_momentary ();
  expand_start_bindings (0);
}  

tree
do_poplevel ()
{
  tree t;

  expand_end_bindings (getdecls (), kept_level_p (), 1);
  t = poplevel (kept_level_p (), 1, 0);
  pop_momentary ();
  return t;
}

tree
tsubst_copy (t, args, nargs, in_decl)
     tree t, *args;
     int nargs;
     tree in_decl;
{
  enum tree_code code;

  if (t == NULL_TREE || t == error_mark_node)
    return t;

  code = TREE_CODE (t);

  switch (code)
    {
    case PARM_DECL:
      return do_identifier (DECL_NAME (t), 0);

    case CONST_DECL:
    case FIELD_DECL:
      if (DECL_CONTEXT (t))
        {
          tree ctx = tsubst (DECL_CONTEXT (t), args, nargs, in_decl);
          if (ctx != DECL_CONTEXT (t))
            return lookup_field (ctx, DECL_NAME (t), 0, 0);
        }
      return t;

    case VAR_DECL:
    case FUNCTION_DECL:
      if (DECL_LANG_SPECIFIC (t) && DECL_TEMPLATE_INFO (t))
        t = tsubst (t, args, nargs, in_decl);
      mark_used (t);
      return t;

#if 0
    case IDENTIFIER_NODE:
      return do_identifier (t, 0);
#endif
      
    case CAST_EXPR:
    case REINTERPRET_CAST_EXPR:
      return build1
        (code, tsubst (TREE_TYPE (t), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl));

    case INDIRECT_REF:
    case PREDECREMENT_EXPR:
    case PREINCREMENT_EXPR:
    case POSTDECREMENT_EXPR:
    case POSTINCREMENT_EXPR:
    case NEGATE_EXPR:
    case TRUTH_NOT_EXPR:
    case ADDR_EXPR:
    case CONVERT_EXPR:      /* Unary + */
    case SIZEOF_EXPR:
    case ARROW_EXPR:
    case THROW_EXPR:
      return build1
        (code, NULL_TREE,
         tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl));

    case PLUS_EXPR:
    case MINUS_EXPR:
    case MULT_EXPR:
    case TRUNC_DIV_EXPR:
    case CEIL_DIV_EXPR:
    case FLOOR_DIV_EXPR:
    case ROUND_DIV_EXPR:
    case EXACT_DIV_EXPR:
    case BIT_AND_EXPR:
    case BIT_ANDTC_EXPR:
    case BIT_IOR_EXPR:
    case BIT_XOR_EXPR:
    case TRUNC_MOD_EXPR:
    case FLOOR_MOD_EXPR:
    case TRUTH_ANDIF_EXPR:
    case TRUTH_ORIF_EXPR:
    case TRUTH_AND_EXPR:
    case TRUTH_OR_EXPR:
    case RSHIFT_EXPR:
    case LSHIFT_EXPR:
    case RROTATE_EXPR:
    case LROTATE_EXPR:
    case EQ_EXPR:
    case NE_EXPR:
    case MAX_EXPR:
    case MIN_EXPR:
    case LE_EXPR:
    case GE_EXPR:
    case LT_EXPR:
    case GT_EXPR:
    case COMPONENT_REF:
    case ARRAY_REF:
    case COMPOUND_EXPR:
    case SCOPE_REF:
    case DOTSTAR_EXPR:
    case MEMBER_REF:
      return build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl));

    case CALL_EXPR:
      {
        tree fn = TREE_OPERAND (t, 0);
        if (really_overloaded_fn (fn))
          fn = tsubst_copy (TREE_VALUE (fn), args, nargs, in_decl);
        else
          fn = tsubst_copy (fn, args, nargs, in_decl);
        return build_nt
          (code, fn, tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl),
           NULL_TREE);
      }

    case METHOD_CALL_EXPR:
      {
        tree name = TREE_OPERAND (t, 0);
        if (TREE_CODE (name) == BIT_NOT_EXPR)
          {
            name = tsubst_copy (TREE_OPERAND (name, 0), args, nargs, in_decl);
            name = build1 (BIT_NOT_EXPR, NULL_TREE, TYPE_MAIN_VARIANT (name));
          }
        else if (TREE_CODE (name) == SCOPE_REF
                 && TREE_CODE (TREE_OPERAND (name, 1)) == BIT_NOT_EXPR)
          {
            tree base = tsubst_copy (TREE_OPERAND (name, 0), args, nargs, in_decl);
            name = TREE_OPERAND (name, 1);
            name = tsubst_copy (TREE_OPERAND (name, 0), args, nargs, in_decl);
            name = build1 (BIT_NOT_EXPR, NULL_TREE, TYPE_MAIN_VARIANT (name));
            name = build_nt (SCOPE_REF, base, name);
          }
        else
          name = tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl);
        return build_nt
          (code, name, tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl),
           tsubst_copy (TREE_OPERAND (t, 2), args, nargs, in_decl),
           NULL_TREE);
      }

    case COND_EXPR:
    case MODOP_EXPR:
      return build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 2), args, nargs, in_decl));

    case NEW_EXPR:
      {
        tree r = build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 2), args, nargs, in_decl));
        NEW_EXPR_USE_GLOBAL (r) = NEW_EXPR_USE_GLOBAL (t);
        return r;
      }

    case DELETE_EXPR:
      {
        tree r = build_nt
        (code, tsubst_copy (TREE_OPERAND (t, 0), args, nargs, in_decl),
         tsubst_copy (TREE_OPERAND (t, 1), args, nargs, in_decl));
        DELETE_EXPR_USE_GLOBAL (r) = DELETE_EXPR_USE_GLOBAL (t);
        DELETE_EXPR_USE_VEC (r) = DELETE_EXPR_USE_VEC (t);
        return r;
      }

    case TREE_LIST:
      {
        tree purpose, value, chain;

        if (t == void_list_node)
          return t;

        purpose = TREE_PURPOSE (t);
        if (purpose)
          purpose = tsubst_copy (purpose, args, nargs, in_decl);
        value = TREE_VALUE (t);
        if (value)
          value = tsubst_copy (value, args, nargs, in_decl);
        chain = TREE_CHAIN (t);
        if (chain && chain != void_type_node)
          chain = tsubst_copy (chain, args, nargs, in_decl);
        if (purpose == TREE_PURPOSE (t)
            && value == TREE_VALUE (t)
            && chain == TREE_CHAIN (t))
          return t;
        return tree_cons (purpose, value, chain);
      }

    case RECORD_TYPE:
    case UNION_TYPE:
    case ENUMERAL_TYPE:
    case INTEGER_TYPE:
    case TEMPLATE_TYPE_PARM:
    case TEMPLATE_CONST_PARM:
    case POINTER_TYPE:
    case REFERENCE_TYPE:
    case OFFSET_TYPE:
    case FUNCTION_TYPE:
    case METHOD_TYPE:
    case ARRAY_TYPE:
    case TYPENAME_TYPE:
      return tsubst (t, args, nargs, in_decl);

    default:
      return t;
    }
}

tree
tsubst_expr (t, args, nargs, in_decl)
     tree t, *args;
     int nargs;
     tree in_decl;
{
  if (t == NULL_TREE || t == error_mark_node)
    return t;

  if (current_template_parms)
    return tsubst_copy (t, args, nargs, in_decl);

  switch (TREE_CODE (t))
    {
    case RETURN_STMT:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      c_expand_return
        (tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl));
      finish_stmt ();
      break;

    case EXPR_STMT:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      t = tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
      /* Do default conversion if safe and possibly important,
         in case within ({...}).  */
      if ((TREE_CODE (TREE_TYPE (t)) == ARRAY_TYPE && lvalue_p (t))
          || TREE_CODE (TREE_TYPE (t)) == FUNCTION_TYPE)
        t = default_conversion (t);
      cplus_expand_expr_stmt (t);
      clear_momentary ();
      finish_stmt ();
      break;

    case DECL_STMT:
      {
        int i = suspend_momentary ();
        tree dcl;

        lineno = TREE_COMPLEXITY (t);
        emit_line_note (input_filename, lineno);
        dcl = start_decl
          (tsubst (TREE_OPERAND (t, 0), args, nargs, in_decl),
           tsubst (TREE_OPERAND (t, 1), args, nargs, in_decl),
           TREE_OPERAND (t, 3) != 0,
           tsubst (TREE_OPERAND (t, 2), args, nargs, in_decl));
        cp_finish_decl
          (dcl, tsubst_expr (TREE_OPERAND (t, 3), args, nargs, in_decl),
           NULL_TREE, 1, LOOKUP_ONLYCONVERTING);
        resume_momentary (i);
        return dcl;
      }

    case FOR_STMT:
      {
        tree tmp;
        int init_scope = (flag_new_for_scope > 0 && TREE_OPERAND (t, 0)
                          && TREE_CODE (TREE_OPERAND (t, 0)) == DECL_STMT);
        int cond_scope = (TREE_OPERAND (t, 1)
                          && TREE_CODE (TREE_OPERAND (t, 1)) == DECL_STMT);

        lineno = TREE_COMPLEXITY (t);
        emit_line_note (input_filename, lineno);
        if (init_scope)
          do_pushlevel ();
        for (tmp = TREE_OPERAND (t, 0); tmp; tmp = TREE_CHAIN (tmp))
          tsubst_expr (tmp, args, nargs, in_decl);
        emit_nop ();
        emit_line_note (input_filename, lineno);
        expand_start_loop_continue_elsewhere (1); 

        if (cond_scope)
          do_pushlevel ();
        tmp = tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        if (tmp)
          expand_exit_loop_if_false (0, condition_conversion (tmp));

        if (! cond_scope)
          do_pushlevel ();
        tsubst_expr (TREE_OPERAND (t, 3), args, nargs, in_decl);
        do_poplevel ();

        emit_line_note (input_filename, lineno);
        expand_loop_continue_here ();
        tmp = tsubst_expr (TREE_OPERAND (t, 2), args, nargs, in_decl);
        if (tmp)
          cplus_expand_expr_stmt (tmp);

        expand_end_loop ();
        if (init_scope)
          do_poplevel ();
        finish_stmt ();
      }
      break;

    case WHILE_STMT:
      {
        tree cond;

        lineno = TREE_COMPLEXITY (t);
        emit_nop ();
        emit_line_note (input_filename, lineno);
        expand_start_loop (1); 

        cond = TREE_OPERAND (t, 0);
        if (TREE_CODE (cond) == DECL_STMT)
          do_pushlevel ();
        cond = tsubst_expr (cond, args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        expand_exit_loop_if_false (0, condition_conversion (cond));

        if (TREE_CODE (TREE_OPERAND (t, 0)) != DECL_STMT)
          do_pushlevel ();
        tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl);
        do_poplevel ();

        expand_end_loop ();
        finish_stmt ();
      }
      break;

    case DO_STMT:
      {
        tree cond;

        lineno = TREE_COMPLEXITY (t);
        emit_nop ();
        emit_line_note (input_filename, lineno);
        expand_start_loop_continue_elsewhere (1); 

        tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
        expand_loop_continue_here ();

        cond = tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        expand_exit_loop_if_false (0, condition_conversion (cond));
        expand_end_loop ();

        clear_momentary ();
        finish_stmt ();
      }
      break;

    case IF_STMT:
      {
        tree tmp;
        int cond_scope = (TREE_CODE (TREE_OPERAND (t, 0)) == DECL_STMT);

        lineno = TREE_COMPLEXITY (t);
        if (cond_scope)
          do_pushlevel ();
        tmp = tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        expand_start_cond (condition_conversion (tmp), 0);
        
        if (tmp = TREE_OPERAND (t, 1), tmp)
          tsubst_expr (tmp, args, nargs, in_decl);

        if (tmp = TREE_OPERAND (t, 2), tmp)
          {
            expand_start_else ();
            tsubst_expr (tmp, args, nargs, in_decl);
          }

        expand_end_cond ();

        if (cond_scope)
          do_poplevel ();

        finish_stmt ();
      }
      break;

    case COMPOUND_STMT:
      {
        tree substmt = TREE_OPERAND (t, 0);

        lineno = TREE_COMPLEXITY (t);

        if (COMPOUND_STMT_NO_SCOPE (t) == 0)
          do_pushlevel ();

        for (; substmt; substmt = TREE_CHAIN (substmt))
          tsubst_expr (substmt, args, nargs, in_decl);

        if (COMPOUND_STMT_NO_SCOPE (t) == 0)
          do_poplevel ();
      }
      break;

    case BREAK_STMT:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      if (! expand_exit_something ())
        error ("break statement not within loop or switch");
      break;

    case SWITCH_STMT:
      {
        tree val, tmp;
        int cond_scope = (TREE_CODE (TREE_OPERAND (t, 0)) == DECL_STMT);

        lineno = TREE_COMPLEXITY (t);
        if (cond_scope)
          do_pushlevel ();
        val = tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl);
        emit_line_note (input_filename, lineno);
        c_expand_start_case (val);
        push_switch ();
        
        if (tmp = TREE_OPERAND (t, 1), tmp)
          tsubst_expr (tmp, args, nargs, in_decl);

        expand_end_case (val);
        pop_switch ();

        if (cond_scope)
          do_poplevel ();

        finish_stmt ();
      }
      break;

    case CASE_LABEL:
      do_case (tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl),
               tsubst_expr (TREE_OPERAND (t, 1), args, nargs, in_decl));
      break;

    case LABEL_DECL:
      t = define_label (DECL_SOURCE_FILE (t), DECL_SOURCE_LINE (t),
                        DECL_NAME (t));
      if (t)
        expand_label (t);
      break;

    case GOTO_STMT:
      lineno = TREE_COMPLEXITY (t);
      emit_line_note (input_filename, lineno);
      if (TREE_CODE (TREE_OPERAND (t, 0)) == IDENTIFIER_NODE)
        {
          tree decl = lookup_label (TREE_OPERAND (t, 0));
          TREE_USED (decl) = 1;
          expand_goto (decl);
        }
      else
        expand_computed_goto
          (tsubst_expr (TREE_OPERAND (t, 0), args, nargs, in_decl));
      break;
          
    default:
      return build_expr_from_tree (tsubst_copy (t, args, nargs, in_decl));
    }
  return NULL_TREE;
}

tree
instantiate_template (tmpl, targ_ptr)
     tree tmpl, *targ_ptr;
{
  tree fndecl;
  int i, len;
  struct obstack *old_fmp_obstack;
  extern struct obstack *function_maybepermanent_obstack;

  push_obstacks (&permanent_obstack, &permanent_obstack);
  old_fmp_obstack = function_maybepermanent_obstack;
  function_maybepermanent_obstack = &permanent_obstack;

  my_friendly_assert (TREE_CODE (tmpl) == TEMPLATE_DECL, 283);
  len = TREE_VEC_LENGTH (DECL_TEMPLATE_PARMS (tmpl));

  i = len;
  while (i--)
    {
      tree t = targ_ptr [i];
      if (TREE_CODE_CLASS (TREE_CODE (t)) == 't')
        {
          tree nt = target_type (t);
          if (IS_AGGR_TYPE (nt) && decl_function_context (TYPE_MAIN_DECL (nt)))
            {
              cp_error ("type `%T' composed from a local class is not a valid template-argument", t);
              cp_error ("  trying to instantiate `%D'", tmpl);
              fndecl = error_mark_node;
              goto out;
            }
        }
      targ_ptr[i] = copy_to_permanent (t);
    }

  /* substitute template parameters */
  fndecl = tsubst (DECL_RESULT (tmpl), targ_ptr, len, tmpl);

 out:
  function_maybepermanent_obstack = old_fmp_obstack;
  pop_obstacks ();

  return fndecl;
}

/* Push the name of the class template into the scope of the instantiation.  */

void
overload_template_name (type)
     tree type;
{
  tree id = DECL_NAME (CLASSTYPE_TI_TEMPLATE (type));
  tree decl;

  if (IDENTIFIER_CLASS_VALUE (id)
      && TREE_TYPE (IDENTIFIER_CLASS_VALUE (id)) == type)
    return;

  decl = build_decl (TYPE_DECL, id, type);
  SET_DECL_ARTIFICIAL (decl);
  pushdecl_class_level (decl);
}

/* Type unification.

   We have a function template signature with one or more references to
   template parameters, and a parameter list we wish to fit to this
   template.  If possible, produce a list of parameters for the template
   which will cause it to fit the supplied parameter list.

   Return zero for success, 2 for an incomplete match that doesn't resolve
   all the types, and 1 for complete failure.  An error message will be
   printed only for an incomplete match.

   TPARMS[NTPARMS] is an array of template parameter types;
   TARGS[NTPARMS] is the array of template parameter values.  PARMS is
   the function template's signature (using TEMPLATE_PARM_IDX nodes),
   and ARGS is the argument list we're trying to match against it.

   If SUBR is 1, we're being called recursively (to unify the arguments of
   a function or method parameter of a function template), so don't zero
   out targs and don't fail on an incomplete match. */

int
type_unification (tparms, targs, parms, args, nsubsts, subr)
     tree tparms, *targs, parms, args;
     int *nsubsts, subr;
{
  tree parm, arg;
  int i;
  int ntparms = TREE_VEC_LENGTH (tparms);

  my_friendly_assert (TREE_CODE (tparms) == TREE_VEC, 289);
  my_friendly_assert (TREE_CODE (parms) == TREE_LIST, 290);
  /* ARGS could be NULL (via a call from parse.y to
     build_x_function_call).  */
  if (args)
    my_friendly_assert (TREE_CODE (args) == TREE_LIST, 291);
  my_friendly_assert (ntparms > 0, 292);

  if (!subr)
    bzero ((char *) targs, sizeof (tree) * ntparms);

  while (parms
         && parms != void_list_node
         && args
         && args != void_list_node)
    {
      parm = TREE_VALUE (parms);
      parms = TREE_CHAIN (parms);
      arg = TREE_VALUE (args);
      args = TREE_CHAIN (args);

      if (arg == error_mark_node)
        return 1;
      if (arg == unknown_type_node)
        return 1;

      if (! uses_template_parms (parm)
          && TREE_CODE_CLASS (TREE_CODE (arg)) != 't')
        {
          if (can_convert_arg (parm, TREE_TYPE (arg), arg))
            continue;
          return 1;
        }
        
#if 0
      if (TREE_CODE (arg) == VAR_DECL)
        arg = TREE_TYPE (arg);
      else if (TREE_CODE_CLASS (TREE_CODE (arg)) == 'e')
        arg = TREE_TYPE (arg);
#else
      if (TREE_CODE_CLASS (TREE_CODE (arg)) != 't')
        {
          my_friendly_assert (TREE_TYPE (arg) != NULL_TREE, 293);
          if (TREE_CODE (arg) == TREE_LIST
              && TREE_TYPE (arg) == unknown_type_node
              && TREE_CODE (TREE_VALUE (arg)) == TEMPLATE_DECL)
            {
              int nsubsts, ntparms;
              tree *targs;

              /* Have to back unify here */
              arg = TREE_VALUE (arg);
              nsubsts = 0;
              ntparms = TREE_VEC_LENGTH (DECL_TEMPLATE_PARMS (arg));
              targs = (tree *) alloca (sizeof (tree) * ntparms);
              parm = tree_cons (NULL_TREE, parm, NULL_TREE);
              return type_unification (DECL_TEMPLATE_PARMS (arg), targs,
                                       TYPE_ARG_TYPES (TREE_TYPE (arg)),
                                       parm, &nsubsts, 0);
            }
          arg = TREE_TYPE (arg);
        }
#endif
      if (TREE_CODE (arg) == REFERENCE_TYPE)
        arg = TREE_TYPE (arg);

      if (TREE_CODE (parm) != REFERENCE_TYPE)
        {
          if (TREE_CODE (arg) == FUNCTION_TYPE
              || TREE_CODE (arg) == METHOD_TYPE)
            arg = build_pointer_type (arg);
          else if (TREE_CODE (arg) == ARRAY_TYPE)
            arg = build_pointer_type (TREE_TYPE (arg));
          else
            arg = TYPE_MAIN_VARIANT (arg);
        }

      switch (unify (tparms, targs, ntparms, parm, arg, nsubsts))
        {
        case 0:
          break;
        case 1:
          return 1;
        }
    }
  /* Fail if we've reached the end of the parm list, and more args
     are present, and the parm list isn't variadic.  */
  if (args && args != void_list_node && parms == void_list_node)
    return 1;
  /* Fail if parms are left and they don't have default values.  */
  if (parms
      && parms != void_list_node
      && TREE_PURPOSE (parms) == NULL_TREE)
    return 1;
  if (!subr)
    for (i = 0; i < ntparms; i++)
      if (!targs[i])
        {
          error ("incomplete type unification");
          return 2;
        }
  return 0;
}

/* Tail recursion is your friend.  */
static int
unify (tparms, targs, ntparms, parm, arg, nsubsts)
     tree tparms, *targs, parm, arg;
     int *nsubsts, ntparms;
{
  int idx;

  /* I don't think this will do the right thing with respect to types.
     But the only case I've seen it in so far has been array bounds, where
     signedness is the only information lost, and I think that will be
     okay.  */
  while (TREE_CODE (parm) == NOP_EXPR)
    parm = TREE_OPERAND (parm, 0);

  if (arg == error_mark_node)
    return 1;
  if (arg == unknown_type_node)
    return 1;
  if (arg == parm)
    return 0;

  switch (TREE_CODE (parm))
    {
    case TEMPLATE_TYPE_PARM:
      (*nsubsts)++;
      idx = TEMPLATE_TYPE_IDX (parm);
#if 0
      /* Template type parameters cannot contain cv-quals; i.e.
         template <class T> void f (T& a, T& b) will not generate
         void f (const int& a, const int& b).  */
      if (TYPE_READONLY (arg) > TYPE_READONLY (parm)
          || TYPE_VOLATILE (arg) > TYPE_VOLATILE (parm))
        return 1;
      arg = TYPE_MAIN_VARIANT (arg);
#else
      {
        int constp = TYPE_READONLY (arg) > TYPE_READONLY (parm);
        int volatilep = TYPE_VOLATILE (arg) > TYPE_VOLATILE (parm);
        arg = cp_build_type_variant (arg, constp, volatilep);
      }
#endif
      /* Simple cases: Value already set, does match or doesn't.  */
      if (targs[idx] == arg)
        return 0;
      else if (targs[idx])
        return 1;
      /* Check for mixed types and values.  */
      if (TREE_CODE (TREE_VALUE (TREE_VEC_ELT (tparms, idx))) != TYPE_DECL)
        return 1;
      targs[idx] = arg;
      return 0;
    case TEMPLATE_CONST_PARM:
      (*nsubsts)++;
      idx = TEMPLATE_CONST_IDX (parm);
      if (targs[idx] == arg)
        return 0;
      else if (targs[idx])
        {
          tree t = targs[idx];
          if (TREE_CODE (t) == TREE_CODE (arg))
            switch (TREE_CODE (arg))
              {
              case INTEGER_CST:
                if (tree_int_cst_equal (t, arg))
                  return 0;
                break;
              case REAL_CST:
                if (REAL_VALUES_EQUAL (TREE_REAL_CST (t), TREE_REAL_CST (arg)))
                  return 0;
                break;
              /* STRING_CST values are not valid template const parms.  */
              default:
                ;
              }
          my_friendly_abort (87);
          return 1;
        }
/*      else if (typeof arg != tparms[idx])
        return 1;*/

      targs[idx] = copy_to_permanent (arg);
      return 0;

    case POINTER_TYPE:
      if (TREE_CODE (arg) != POINTER_TYPE)
        return 1;
      return unify (tparms, targs, ntparms, TREE_TYPE (parm), TREE_TYPE (arg),
                    nsubsts);

    case REFERENCE_TYPE:
      if (TREE_CODE (arg) == REFERENCE_TYPE)
        arg = TREE_TYPE (arg);
      return unify (tparms, targs, ntparms, TREE_TYPE (parm), arg, nsubsts);

    case ARRAY_TYPE:
      if (TREE_CODE (arg) != ARRAY_TYPE)
        return 1;
      if (unify (tparms, targs, ntparms, TYPE_DOMAIN (parm), TYPE_DOMAIN (arg),
                 nsubsts) != 0)
        return 1;
      return unify (tparms, targs, ntparms, TREE_TYPE (parm), TREE_TYPE (arg),
                    nsubsts);

    case REAL_TYPE:
    case INTEGER_TYPE:
      if (TREE_CODE (arg) != TREE_CODE (parm))
        return 1;

      if (TREE_CODE (parm) == INTEGER_TYPE)
        {
          if (TYPE_MIN_VALUE (parm) && TYPE_MIN_VALUE (arg)
              && unify (tparms, targs, ntparms,
                        TYPE_MIN_VALUE (parm), TYPE_MIN_VALUE (arg), nsubsts))
            return 1;
          if (TYPE_MAX_VALUE (parm) && TYPE_MAX_VALUE (arg)
              && unify (tparms, targs, ntparms,
                        TYPE_MAX_VALUE (parm), TYPE_MAX_VALUE (arg), nsubsts))
            return 1;
        }
      /* As far as unification is concerned, this wins.  Later checks
         will invalidate it if necessary.  */
      return 0;

      /* Types INTEGER_CST and MINUS_EXPR can come from array bounds.  */
    case INTEGER_CST:
      if (TREE_CODE (arg) != INTEGER_CST)
        return 1;
      return !tree_int_cst_equal (parm, arg);

    case MINUS_EXPR:
      {
        tree t1, t2;
        t1 = TREE_OPERAND (parm, 0);
        t2 = TREE_OPERAND (parm, 1);
        return unify (tparms, targs, ntparms, t1,
                      fold (build (PLUS_EXPR, integer_type_node, arg, t2)),
                      nsubsts);
      }

    case TREE_VEC:
      {
        int i;
        if (TREE_CODE (arg) != TREE_VEC)
          return 1;
        if (TREE_VEC_LENGTH (parm) != TREE_VEC_LENGTH (arg))
          return 1;
        for (i = TREE_VEC_LENGTH (parm) - 1; i >= 0; i--)
          if (unify (tparms, targs, ntparms,
                     TREE_VEC_ELT (parm, i), TREE_VEC_ELT (arg, i),
                     nsubsts))
            return 1;
        return 0;
      }

    case RECORD_TYPE:
      if (TYPE_PTRMEMFUNC_FLAG (parm))
        return unify (tparms, targs, ntparms, TYPE_PTRMEMFUNC_FN_TYPE (parm),
                      arg, nsubsts);

      /* Allow trivial conversions.  */
      if (TREE_CODE (arg) != RECORD_TYPE
          || TYPE_READONLY (parm) < TYPE_READONLY (arg)
          || TYPE_VOLATILE (parm) < TYPE_VOLATILE (arg))
        return 1;

      if (CLASSTYPE_TEMPLATE_INFO (parm) && CLASSTYPE_TEMPLATE_INFO (arg)
          && uses_template_parms (parm))
        {
          if (CLASSTYPE_TI_TEMPLATE (parm) != CLASSTYPE_TI_TEMPLATE (arg))
            return 1;
          return unify (tparms, targs, ntparms, CLASSTYPE_TI_ARGS (parm),
                        CLASSTYPE_TI_ARGS (arg), nsubsts);
        }
      else if (TYPE_MAIN_VARIANT (parm) != TYPE_MAIN_VARIANT (arg))
        return 1;
      return 0;

    case METHOD_TYPE:
      if (TREE_CODE (arg) != METHOD_TYPE)
        return 1;
      goto check_args;

    case FUNCTION_TYPE:
      if (TREE_CODE (arg) != FUNCTION_TYPE)
        return 1;
     check_args:
      if (unify (tparms, targs, ntparms, TREE_TYPE (parm),
                 TREE_TYPE (arg), nsubsts))
        return 1;
      return type_unification (tparms, targs, TYPE_ARG_TYPES (parm),
                               TYPE_ARG_TYPES (arg), nsubsts, 1);

    case OFFSET_TYPE:
      if (TREE_CODE (arg) != OFFSET_TYPE)
        return 1;
      if (unify (tparms, targs, ntparms, TYPE_OFFSET_BASETYPE (parm),
                 TYPE_OFFSET_BASETYPE (arg), nsubsts))
        return 1;
      return unify (tparms, targs, ntparms, TREE_TYPE (parm),
                    TREE_TYPE (arg), nsubsts);

    default:
      sorry ("use of `%s' in template type unification",
             tree_code_name [(int) TREE_CODE (parm)]);
      return 1;
    }
}
\f
void
mark_decl_instantiated (result, extern_p)
     tree result;
     int extern_p;
{
  if (DECL_TEMPLATE_INSTANTIATION (result))
    SET_DECL_EXPLICIT_INSTANTIATION (result);
  TREE_PUBLIC (result) = 1;

  if (! extern_p)
    {
      DECL_INTERFACE_KNOWN (result) = 1;
      DECL_NOT_REALLY_EXTERN (result) = 1;
    }
}

/* called from the parser.  */
void
do_function_instantiation (declspecs, declarator, storage)
     tree declspecs, declarator, storage;
{
  tree decl = grokdeclarator (declarator, declspecs, NORMAL, 0,
                              NULL_TREE, NULL_TREE);
  tree name;
  tree fn;
  tree result = NULL_TREE;
  int extern_p = 0;

  if (! DECL_LANG_SPECIFIC (decl))
    {
      cp_error ("explicit instantiation of non-template `%#D'", decl);
      return;
    }

  /* If we've already seen this template instance, use it.  */
  if (name = DECL_ASSEMBLER_NAME (decl),
      fn = IDENTIFIER_GLOBAL_VALUE (name),
      fn && DECL_TEMPLATE_INSTANTIATION (fn))
    result = fn;
  else if (fn && DECL_CONTEXT (fn))
    ;
  else if (name = DECL_NAME (decl), fn = IDENTIFIER_GLOBAL_VALUE (name), fn)
    {
      for (fn = get_first_fn (fn); fn; fn = DECL_CHAIN (fn))
        if (decls_match (fn, decl)
            && DECL_DEFER_OUTPUT (fn))
          {
            result = fn;
            break;
          }
        else if (TREE_CODE (fn) == TEMPLATE_DECL)
          {
            int ntparms = TREE_VEC_LENGTH (DECL_TEMPLATE_PARMS (fn));
            tree *targs = (tree *) malloc (sizeof (tree) * ntparms);
            int i, dummy = 0;
            i = type_unification (DECL_TEMPLATE_PARMS (fn), targs,
                                  TYPE_ARG_TYPES (TREE_TYPE (fn)),
                                  TYPE_ARG_TYPES (TREE_TYPE (decl)),
                                  &dummy, 0);
            if (i == 0)
              {
                if (result)
                  cp_error ("ambiguous template instantiation for `%D' requested", decl);
                else
                  result = instantiate_template (fn, targs);
              }
            free (targs);
          }
    }
  if (! result)
    {
      cp_error ("no matching template for `%D' found", decl);
      return;
    }

  if (flag_external_templates)
    return;

  if (storage == NULL_TREE)
    ;
  else if (storage == ridpointers[(int) RID_EXTERN])
    extern_p = 1;
  else
    cp_error ("storage class `%D' applied to template instantiation",
              storage);

  if (! extern_p)
    instantiate_decl (result);
  mark_decl_instantiated (result, extern_p);
  repo_template_instantiated (result, extern_p);
}

void
mark_class_instantiated (t, extern_p)
     tree t;
     int extern_p;
{
  SET_CLASSTYPE_EXPLICIT_INSTANTIATION (t);
  SET_CLASSTYPE_INTERFACE_KNOWN (t);
  CLASSTYPE_INTERFACE_ONLY (t) = extern_p;
  CLASSTYPE_VTABLE_NEEDS_WRITING (t) = ! extern_p;
  TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (t)) = extern_p;
  if (! extern_p)
    {
      CLASSTYPE_DEBUG_REQUESTED (t) = 1;
      rest_of_type_compilation (t, 1);
    }
}     

void
do_type_instantiation (name, storage)
     tree name, storage;
{
  tree t = TREE_TYPE (name);
  int extern_p = 0;
  int nomem_p = 0;
  int static_p = 0;

  complete_type (t);

  /* With -fexternal-templates, explicit instantiations are treated the same
     as implicit ones.  */
  if (flag_external_templates)
    return;

  if (TYPE_SIZE (t) == NULL_TREE)
    {
      cp_error ("explicit instantiation of `%#T' before definition of template",
                t);
      return;
    }

  if (storage == NULL_TREE)
    /* OK */;
  else if (storage == ridpointers[(int) RID_INLINE])
    nomem_p = 1;
  else if (storage == ridpointers[(int) RID_EXTERN])
    extern_p = 1;
  else if (storage == ridpointers[(int) RID_STATIC])
    static_p = 1;
  else
    {
      cp_error ("storage class `%D' applied to template instantiation",
                storage);
      extern_p = 0;
    }

  /* We've already instantiated this.  */
  if (CLASSTYPE_EXPLICIT_INSTANTIATION (t) && ! CLASSTYPE_INTERFACE_ONLY (t)
      && extern_p)
    return;

  if (! CLASSTYPE_TEMPLATE_SPECIALIZATION (t))
    {
      mark_class_instantiated (t, extern_p);
      repo_template_instantiated (t, extern_p);
    }

  if (nomem_p)
    return;

  {
    tree tmp;

    if (! static_p)
      for (tmp = TYPE_METHODS (t); tmp; tmp = TREE_CHAIN (tmp))
        if (DECL_TEMPLATE_INSTANTIATION (tmp))
          {
            mark_decl_instantiated (tmp, extern_p);
            repo_template_instantiated (tmp, extern_p);
            if (! extern_p)
              instantiate_decl (tmp);
          }

    for (tmp = TYPE_FIELDS (t); tmp; tmp = TREE_CHAIN (tmp))
      if (TREE_CODE (tmp) == VAR_DECL && DECL_TEMPLATE_INSTANTIATION (tmp))
        {
          mark_decl_instantiated (tmp, extern_p);
          repo_template_instantiated (tmp, extern_p);
          if (! extern_p)
            instantiate_decl (tmp);
        }

    for (tmp = CLASSTYPE_TAGS (t); tmp; tmp = TREE_CHAIN (tmp))
      if (IS_AGGR_TYPE (TREE_VALUE (tmp)))
        do_type_instantiation (TYPE_MAIN_DECL (TREE_VALUE (tmp)), storage);
  }
}

tree
instantiate_decl (d)
     tree d;
{
  tree ti = DECL_TEMPLATE_INFO (d);
  tree tmpl = TI_TEMPLATE (ti);
  tree args = TI_ARGS (ti);
  tree td;
  tree pattern = DECL_TEMPLATE_RESULT (tmpl);
  tree save_ti;
  int nested = in_function_p ();
  int d_defined;
  int pattern_defined;

  if (TREE_CODE (d) == FUNCTION_DECL)
    {
      d_defined = (DECL_INITIAL (d) != NULL_TREE);
      pattern_defined = (DECL_INITIAL (pattern) != NULL_TREE);
    }
  else
    {
      d_defined = ! DECL_IN_AGGR_P (d);
      pattern_defined = ! DECL_IN_AGGR_P (pattern);
    }

  if (d_defined)
    return d;
  else if (pattern_defined)
    {
      repo_template_used (d);

      if (flag_external_templates && ! DECL_INTERFACE_KNOWN (d))
        {
          if (flag_alt_external_templates)
            {
              if (interface_unknown)
                warn_if_unknown_interface (d);
            }
          else if (DECL_INTERFACE_KNOWN (pattern))
            {
              DECL_INTERFACE_KNOWN (d) = 1;
              DECL_NOT_REALLY_EXTERN (d) = ! DECL_EXTERNAL (pattern);
            }
          else
            warn_if_unknown_interface (pattern);
        }

      if (at_eof && ! DECL_INLINE (d))
        import_export_decl (d);
    }

  if (! pattern_defined
      || (TREE_CODE (d) == FUNCTION_DECL && ! DECL_INLINE (d)
          && (! DECL_INTERFACE_KNOWN (d)
              || ! DECL_NOT_REALLY_EXTERN (d))))
    {
      add_pending_template (d);
      return d;
    }

  if (! push_tinst_level (d))
    return d;

  if (TREE_CODE (d) == FUNCTION_DECL && nested)
    push_cp_function_context (NULL_TREE);
  push_to_top_level ();

  /* Trick tsubst into giving us a new decl in case the template changed.  */
  save_ti = DECL_TEMPLATE_INFO (pattern);
  DECL_TEMPLATE_INFO (pattern) = NULL_TREE;
  td = tsubst (pattern, &TREE_VEC_ELT (args, 0), TREE_VEC_LENGTH (args), tmpl);
  DECL_TEMPLATE_INFO (pattern) = save_ti;

  /* Convince duplicate_decls to use the DECL_ARGUMENTS from the new decl.  */
  if (TREE_CODE (d) == FUNCTION_DECL)
    DECL_INITIAL (td) = error_mark_node;
  duplicate_decls (td, d);
  if (TREE_CODE (d) == FUNCTION_DECL)
    DECL_INITIAL (td) = 0;

  if (TREE_CODE (d) == VAR_DECL)
    {
      DECL_IN_AGGR_P (d) = 0;
      if (DECL_INTERFACE_KNOWN (d))
        DECL_EXTERNAL (d) = ! DECL_NOT_REALLY_EXTERN (d);
      else
        {
          DECL_EXTERNAL (d) = 1;
          DECL_NOT_REALLY_EXTERN (d) = 1;
        }
      cp_finish_decl (d, DECL_INITIAL (d), NULL_TREE, 0, 0);
    }
  else if (TREE_CODE (d) == FUNCTION_DECL)
    {
      tree t = DECL_SAVED_TREE (pattern);
      int line = lineno;
      char *file = input_filename;

      lineno = DECL_SOURCE_LINE (d);
      input_filename = DECL_SOURCE_FILE (d);

      start_function (NULL_TREE, d, NULL_TREE, NULL_TREE, 1);
      store_parm_decls ();

      if (t && TREE_CODE (t) == RETURN_INIT)
        {
          store_return_init
            (TREE_OPERAND (t, 0),
             tsubst_expr (TREE_OPERAND (t, 1), &TREE_VEC_ELT (args, 0),
                          TREE_VEC_LENGTH (args), tmpl));
          t = TREE_CHAIN (t);
        }

      if (t && TREE_CODE (t) == CTOR_INITIALIZER)
        {
          current_member_init_list
            = tsubst_expr_values (TREE_OPERAND (t, 0), args);
          current_base_init_list
            = tsubst_expr_values (TREE_OPERAND (t, 1), args);
          t = TREE_CHAIN (t);
        }

      setup_vtbl_ptr ();
      /* Always keep the BLOCK node associated with the outermost
         pair of curley braces of a function.  These are needed
         for correct operation of dwarfout.c.  */
      keep_next_level ();

      my_friendly_assert (TREE_CODE (t) == COMPOUND_STMT, 42);
      tsubst_expr (t, &TREE_VEC_ELT (args, 0),
                   TREE_VEC_LENGTH (args), tmpl);

      finish_function (lineno, 0, nested);

      lineno = line;
      input_filename = file;
    }

  pop_from_top_level ();
  if (TREE_CODE (d) == FUNCTION_DECL && nested)
    pop_cp_function_context (NULL_TREE);
  pop_tinst_level ();

  return d;
}

tree
tsubst_chain (t, argvec)
     tree t, argvec;
{
  if (t)
    {
      tree first = tsubst (t, &TREE_VEC_ELT (argvec, 0),
                           TREE_VEC_LENGTH (argvec), NULL_TREE);
      tree last = first;

      for (t = TREE_CHAIN (t); t; t = TREE_CHAIN (t))
        {
          tree x = tsubst (t, &TREE_VEC_ELT (argvec, 0),
                           TREE_VEC_LENGTH (argvec), NULL_TREE);
          TREE_CHAIN (last) = x;
          last = x;
        }

      return first;
    }
  return NULL_TREE;
}

tree
tsubst_expr_values (t, argvec)
     tree t, argvec;
{
  tree first = NULL_TREE;
  tree *p = &first;

  for (; t; t = TREE_CHAIN (t))
    {
      tree pur = tsubst_copy (TREE_PURPOSE (t), &TREE_VEC_ELT (argvec, 0),
                              TREE_VEC_LENGTH (argvec), NULL_TREE);
      tree val = tsubst_expr (TREE_VALUE (t), &TREE_VEC_ELT (argvec, 0),
                              TREE_VEC_LENGTH (argvec), NULL_TREE);
      *p = build_tree_list (pur, val);
      p = &TREE_CHAIN (*p);
    }
  return first;
}

tree last_tree;

void
add_tree (t)
     tree t;
{
  last_tree = TREE_CHAIN (last_tree) = t;
}