Initial revision

From-SVN: r6613

1 files changed, 998 insertions, 0 deletions

diff --git a/gcc/cp/sig.c b/gcc/cp/sig.c
new file mode 100644
index 0000000..979d7aa
--- /dev/null
+++ b/gcc/cp/sig.c
@@ -0,0 +1,998 @@
+/* Functions dealing with signatures and signature pointers/references.
+   Copyright (C) 1992 Free Software Foundation, Inc.
+   Contributed by Gerald Baumgartner (gb@cs.purdue.edu)
+
+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, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+
+#include "config.h"
+#include <stdio.h>
+#include "obstack.h"
+#include "tree.h"
+#include "cp-tree.h"
+#include "flags.h"
+#include "assert.h"
+
+extern struct obstack *current_obstack;
+extern struct obstack permanent_obstack;
+extern struct obstack *saveable_obstack;
+
+extern void error ();
+extern void sorry ();
+extern void compiler_error ();
+extern void make_decl_rtl			PROTO((tree, char *, int));
+
+/* Used to help generate globally unique names for signature tables.  */
+
+static int global_sigtable_name_counter;
+
+/* Build an identifier for a signature pointer or reference, so we
+   can use it's name in function name mangling.  */
+
+static tree
+build_signature_pointer_or_reference_name (to_type, constp, volatilep, refp)
+     tree to_type;
+     int constp, volatilep, refp;
+{
+  char * sig_name = TYPE_NAME_STRING (to_type);
+  int name_len = TYPE_NAME_LENGTH (to_type) + constp + volatilep;
+  char * name;
+
+  if (refp)
+    {
+      name = (char *) alloca (name_len + sizeof (SIGNATURE_REFERENCE_NAME) +2);
+      sprintf (name, SIGNATURE_REFERENCE_NAME_FORMAT,
+	       constp ? "C" : "", volatilep ? "V": "", sig_name);
+    }
+  else
+    {
+      name = (char *) alloca (name_len + sizeof (SIGNATURE_POINTER_NAME) + 2);
+      sprintf (name, SIGNATURE_POINTER_NAME_FORMAT,
+	       constp ? "C" : "", volatilep ? "V": "", sig_name);
+    }
+  return get_identifier (name);
+}
+
+/* Build a DECL node for a signature pointer or reference, so we can
+   tell the debugger the structure of signature pointers/references.
+   This function is called at most eight times for a given signature,
+   once for each [const] [volatile] signature pointer/reference.  */
+
+static void
+build_signature_pointer_or_reference_decl (type, name)
+     tree type, name;
+{
+  tree decl;
+
+  /* We don't enter this declaration in any sort of symbol table.  */
+  decl = build_decl (TYPE_DECL, name, type);
+  TYPE_NAME (type) = decl;
+  TREE_CHAIN (type) = decl;
+}
+
+/* Construct, lay out and return the type of pointers or references
+   to signature TO_TYPE.  If such a type has already been constructed,
+   reuse it. If CONSTP or VOLATILEP is specified, make the `optr' const
+   or volatile, respectively.   If we are constructing a const/volatile
+   type variant and the main type variant doesn't exist yet, it is built
+   as well.  If REFP is 1, we construct a signature reference, otherwise
+   a signature pointer is constructed.
+
+   This function is a subroutine of `build_signature_pointer_type' and
+   `build_signature_reference_type'.  */
+
+static tree
+build_signature_pointer_or_reference_type (to_type, constp, volatilep, refp)
+     tree to_type;
+     int constp, volatilep, refp;
+{
+  register tree t, m;
+  register struct obstack *ambient_obstack = current_obstack;
+  register struct obstack *ambient_saveable_obstack = saveable_obstack;
+
+  m = refp ? SIGNATURE_REFERENCE_TO (to_type) : SIGNATURE_POINTER_TO (to_type);
+
+  /* If we don't have the main variant yet, construct it.  */
+  if (m == NULL_TREE
+      && (constp || volatilep))
+    m = build_signature_pointer_or_reference_type (to_type, 0, 0, refp);
+
+  /* Treat any nonzero argument as 1.  */
+  constp = !!constp;
+  volatilep = !!volatilep;
+  refp = !!refp;
+
+  /* If not generating auxiliary info, search the chain of variants to see
+     if there is already one there just like the one we need to have.  If so,
+     use that existing one.
+
+     We don't do this in the case where we are generating aux info because
+     in that case we want each typedef names to get it's own distinct type
+     node, even if the type of this new typedef is the same as some other
+     (existing) type.  */
+
+  if (m && !flag_gen_aux_info)
+    for (t = m; t; t = TYPE_NEXT_VARIANT (t))
+      if (constp == TYPE_READONLY (TREE_TYPE (TREE_TYPE (TYPE_FIELDS (t))))
+	  && volatilep == TYPE_VOLATILE (TREE_TYPE (TREE_TYPE (TYPE_FIELDS (t)))))
+        return t;
+
+  /* We need a new one.  If TO_TYPE is permanent, make this permanent too.  */
+  if (TREE_PERMANENT (to_type))
+    {
+      current_obstack = &permanent_obstack;
+      saveable_obstack = &permanent_obstack;
+    }
+
+  /* A signature pointer or reference to a signature `s' looks like this:
+
+       struct {
+         void * optr;
+	 const s * sptr;
+	 vtbl_type_node * vptr;
+       };
+
+     A `const' signature pointer/reference is a
+
+       struct {
+         const void * optr;
+	 const s * sptr;
+	 vtbl_type_node * vptr;
+       };
+
+     Similarly, for `volatile' and `const volatile'.
+   */
+
+  t = make_lang_type (RECORD_TYPE);
+  {
+    tree obj_type = build_type_variant (void_type_node, constp, volatilep);
+    tree optr_type = build_pointer_type (obj_type);
+    tree optr, sptr, vptr;
+
+    optr = build_lang_field_decl (FIELD_DECL,
+				  get_identifier (SIGNATURE_OPTR_NAME),
+				  optr_type);
+    DECL_FIELD_CONTEXT (optr) = t;
+    DECL_CLASS_CONTEXT (optr) = t;
+
+    if (m)
+      {
+	/* We can share `sptr' and `vptr' among type variants.  */
+	sptr = TREE_CHAIN (TYPE_FIELDS (m));
+	vptr = TREE_CHAIN (sptr);
+      }
+    else
+      {
+	tree sig_tbl_type = build_type_variant (to_type, 1, 0);
+	
+	sptr = build_lang_field_decl (FIELD_DECL,
+				      get_identifier (SIGNATURE_SPTR_NAME),
+				      build_pointer_type (sig_tbl_type));
+	vptr = build_lang_field_decl (FIELD_DECL,
+				      get_identifier (SIGNATURE_VPTR_NAME),
+				      build_pointer_type (vtbl_type_node));
+	DECL_FIELD_CONTEXT (sptr) = t;
+	DECL_CLASS_CONTEXT (sptr) = t;
+	DECL_FIELD_CONTEXT (vptr) = t;
+	DECL_CLASS_CONTEXT (vptr) = t;
+	TREE_CHAIN (sptr) = vptr;
+	TREE_CHAIN (vptr) = NULL_TREE;
+      }
+
+    TREE_CHAIN (optr) = sptr;
+    TYPE_FIELDS (t) = optr;
+    /* To make `build_vfn_ref' work when building a signature method call.  */
+    CLASSTYPE_VFIELD (t) = vptr;
+    DECL_FCONTEXT (CLASSTYPE_VFIELD (t)) = t;
+    TYPE_ALIGN (t) = TYPE_ALIGN (optr_type);
+  }
+
+  {
+    tree name = build_signature_pointer_or_reference_name (to_type, constp,
+							   volatilep, refp);
+
+    /* Build a DECL node for this type, so the debugger has access to it.  */
+    build_signature_pointer_or_reference_decl (t, name);
+  }
+
+  CLASSTYPE_GOT_SEMICOLON (t) = 1;
+  IS_SIGNATURE_POINTER (t) = ! refp;
+  IS_SIGNATURE_REFERENCE (t) = refp;
+  SIGNATURE_TYPE (t) = to_type;
+
+  if (m)
+    {
+      /* Add this type to the chain of variants of TYPE.
+	 Every type has to be its own TYPE_MAIN_VARIANT.  */
+      TYPE_NEXT_VARIANT (t) = TYPE_NEXT_VARIANT (m);
+      TYPE_NEXT_VARIANT (m) = t;
+    }
+  else if (refp)
+    /* Record this type as the reference to TO_TYPE.  */
+    SIGNATURE_REFERENCE_TO (to_type) = t;
+  else
+    /* Record this type as the pointer to TO_TYPE.  */
+    SIGNATURE_POINTER_TO (to_type) = t;
+
+  /* Lay out the type.  This function has many callers that are concerned
+     with expression-construction, and this simplifies them all.
+     Also, it guarantees the TYPE_SIZE is permanent if the type is.  */
+  layout_type (t);
+
+  current_obstack = ambient_obstack;
+  saveable_obstack = ambient_saveable_obstack;
+
+  /* Ouput debug information for this type.  */
+  rest_of_type_compilation (t, 1);
+
+  return t;
+}
+
+/* Construct, lay out and return the type of pointers to signature TO_TYPE.  */
+
+tree
+build_signature_pointer_type (to_type, constp, volatilep)
+     tree to_type;
+     int constp, volatilep;
+{
+  return
+    build_signature_pointer_or_reference_type (to_type, constp, volatilep, 0);
+}
+
+/* Construct, lay out and return the type of pointers to signature TO_TYPE.  */
+
+tree
+build_signature_reference_type (to_type, constp, volatilep)
+     tree to_type;
+     int constp, volatilep;
+{
+  return
+    build_signature_pointer_or_reference_type (to_type, constp, volatilep, 1);
+}
+
+/* Return the name of the signature table (as an IDENTIFIER_NODE)
+   for the given signature type SIG_TYPE and rhs type RHS_TYPE.  */
+
+static tree
+get_sigtable_name (sig_type, rhs_type)
+     tree sig_type, rhs_type;
+{
+  tree sig_type_id = build_typename_overload (sig_type);
+  tree rhs_type_id = build_typename_overload (rhs_type);
+  char *buf = (char *) alloca (sizeof (SIGTABLE_NAME_FORMAT_LONG)
+			       + IDENTIFIER_LENGTH (sig_type_id)
+			       + IDENTIFIER_LENGTH (rhs_type_id) + 20);
+  char *sig_ptr = IDENTIFIER_POINTER (sig_type_id);
+  char *rhs_ptr = IDENTIFIER_POINTER (rhs_type_id);
+  int i, j;
+
+  for (i = 0; sig_ptr[i] == OPERATOR_TYPENAME_FORMAT[i]; i++)
+    /* do nothing */;
+  while (sig_ptr[i] >= '0' && sig_ptr[i] <= '9')
+    i += 1;
+
+  for (j = 0; rhs_ptr[j] == OPERATOR_TYPENAME_FORMAT[j]; j++)
+    /* do nothing */;
+  while (rhs_ptr[j] >= '0' && rhs_ptr[j] <= '9')
+    j += 1;
+
+  if (IS_SIGNATURE (rhs_type))
+    sprintf (buf, SIGTABLE_NAME_FORMAT_LONG, sig_ptr+i, rhs_ptr+j,
+	     global_sigtable_name_counter++);
+  else
+    sprintf (buf, SIGTABLE_NAME_FORMAT, sig_ptr+i, rhs_ptr+j);
+  return get_identifier (buf);
+}
+
+/* Build a field decl that points to a signature member function.  */
+
+static tree
+build_member_function_pointer (member)
+     tree member;
+{
+  char *namstr = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (member));
+  int namlen = IDENTIFIER_LENGTH (DECL_ASSEMBLER_NAME (member));
+  char *name;
+  tree entry;
+  
+  name = (char *) alloca (namlen + sizeof (SIGNATURE_FIELD_NAME) + 2);
+  sprintf (name, SIGNATURE_FIELD_NAME_FORMAT, namstr);
+
+  /* @@ Do we really want to xref signature table fields?  */
+  GNU_xref_ref (current_function_decl, name);
+
+  entry = build_lang_field_decl (FIELD_DECL, get_identifier (name),
+				 TYPE_MAIN_VARIANT (sigtable_entry_type));
+  TREE_CONSTANT (entry) = 1;
+  TREE_READONLY (entry) = 1;
+
+  /* @@ Do we really want to xref signature table fields?  */
+  GNU_xref_decl (current_function_decl, entry);
+
+  return entry;
+}
+
+/* For each FUNCTION_DECL in a signature we construct a member function
+   pointer of the appropriate type.  We also need two flags to test
+   whether the member function pointer points to a virtual function or
+   to a default implementation.  Those flags will be the two lower order
+   bits of the member function pointer (or the two higher order bits,
+   based on the configuration).
+
+   The new FIELD_DECLs are appended at the end of the last (and only)
+   sublist of `list_of_fieldlists.'
+
+   As a side effect, each member function in the signature gets the
+   `decl.ignored' bit turned on, so we don't output debug info for it.  */
+
+void
+append_signature_fields (list_of_fieldlists)
+     tree list_of_fieldlists;
+{
+  tree l, x;
+  tree last_x = NULL_TREE;
+  tree mfptr;
+  tree last_mfptr;
+  tree mfptr_list = NULL_TREE;
+	      
+  /* For signatures it should actually be only a list with one element.  */
+  for (l = list_of_fieldlists; l; l = TREE_CHAIN (l))
+    {
+      for (x = TREE_VALUE (l); x; x = TREE_CHAIN (x))
+	{
+	  if (TREE_CODE (x) == FUNCTION_DECL)
+	    {
+	      mfptr = build_member_function_pointer (x);
+	      DECL_MEMFUNC_POINTER_TO (x) = mfptr;
+	      DECL_MEMFUNC_POINTING_TO (mfptr) = x;
+	      DECL_IGNORED_P (x) = 1;
+	      DECL_IN_AGGR_P (mfptr) = 1;
+	      if (! mfptr_list)
+		mfptr_list = last_mfptr = mfptr;
+	      else
+		{
+		  TREE_CHAIN (last_mfptr) = mfptr;
+		  last_mfptr = mfptr;
+		}
+	    }
+	  last_x = x;
+	}
+    }
+
+  /* Append the lists.  */
+  if (last_x && mfptr_list)
+    {
+      TREE_CHAIN (last_x) = mfptr_list;
+      TREE_CHAIN (last_mfptr) = NULL_TREE;
+    }
+}
+
+/* Compare the types of a signature member function and a class member
+   function.  Returns 1 if the types are in the C++ `<=' relationship.
+
+   If we have a signature pointer/reference as argument or return type
+   we don't want to do a recursive conformance check.  The conformance
+   check only succeeds if both LHS and RHS refer to the same signature
+   pointer.  Otherwise we need to keep information about parameter types
+   around at run time to initialize the signature table correctly.  */
+
+static int
+match_method_types (sig_mtype, class_mtype)
+     tree sig_mtype, class_mtype;
+{
+  tree sig_return_type = TREE_TYPE (sig_mtype);
+  tree sig_arg_types = TYPE_ARG_TYPES (sig_mtype);
+  tree class_return_type = TREE_TYPE (class_mtype);
+  tree class_arg_types = TYPE_ARG_TYPES (class_mtype);
+
+  /* The return types have to be the same.  */
+  if (! comptypes (sig_return_type, class_return_type, 1))
+    return 0;
+
+  /* Compare the first argument `this.'  */
+  {
+    /* Get the type of what the `optr' is pointing to.  */
+    tree sig_this =
+      TREE_TYPE (TREE_TYPE (TYPE_FIELDS (TREE_VALUE (sig_arg_types))));
+    tree class_this = TREE_VALUE (class_arg_types);
+
+    if (TREE_CODE (class_this) == RECORD_TYPE)	/* Is `this' a sig ptr?  */
+      class_this = TREE_TYPE (TREE_TYPE (TYPE_FIELDS (class_this)));
+    else
+      class_this = TREE_TYPE (class_this);
+
+    /* If a signature method's `this' is const or volatile, so has to be
+       the corresponding class method's `this.'  */
+    if ((TYPE_READONLY (sig_this) && ! TYPE_READONLY (class_this))
+	|| (TYPE_VOLATILE (sig_this) && ! TYPE_VOLATILE (class_this)))
+      return 0;
+  }
+
+  sig_arg_types = TREE_CHAIN (sig_arg_types);
+  class_arg_types = TREE_CHAIN (class_arg_types);
+
+  /* The number of arguments and the argument types have to be the same.  */
+  return compparms (sig_arg_types, class_arg_types, 3);
+}
+
+/* Undo casts of opaque type variables to the RHS types.  */
+static void
+undo_casts (sig_ty)
+     tree sig_ty;
+{
+  tree field = TYPE_FIELDS (sig_ty);
+
+  /* Since all the FIELD_DECLs for the signature table entries are at the end
+     of the chain (see `append_signature_fields'), we can do it this way.  */
+  for (; field && TREE_CODE (field) != FIELD_DECL; field = TREE_CHAIN (field))
+    if (TYPE_MAIN_VARIANT (TREE_TYPE (field)) == opaque_type_node)
+      TREE_TYPE (TREE_TYPE (field)) = TREE_TYPE (ptr_type_node);
+}
+
+/* Do the type checking necessary to see whether the `rhs' conforms to
+   the lhs's `sig_ty'.  Depending on the type of `rhs' return a NULL_TREE,
+   an integer_zero_node, a constructor, or an expression offsetting the
+   `rhs' signature table.  */
+
+static tree
+build_signature_table_constructor (sig_ty, rhs)
+     tree sig_ty, rhs;
+{
+  tree rhstype = TREE_TYPE (rhs);
+  tree sig_field = TYPE_FIELDS (sig_ty);
+  tree result = NULL_TREE;
+  tree first_rhs_field = NULL_TREE;
+  tree last_rhs_field;
+  int sig_ptr_p = IS_SIGNATURE (rhstype);
+  int offset_p = sig_ptr_p;
+
+  rhstype = sig_ptr_p ? rhstype : TREE_TYPE (rhstype);
+
+  if (CLASSTYPE_TAGS (sig_ty))
+    {
+      sorry ("conformance check with signature containing class declarations");
+      return error_mark_node;
+    }
+
+  for (; sig_field; sig_field = TREE_CHAIN (sig_field))
+    {
+      tree basetype_path, baselink, basetypes;
+      tree sig_method, sig_mname, sig_mtype;
+      tree rhs_method, tbl_entry;
+
+      if (TREE_CODE (sig_field) == TYPE_DECL)
+	{
+	  tree sig_field_type = TREE_TYPE (sig_field);
+
+	  if (TYPE_MAIN_VARIANT (sig_field_type) == opaque_type_node)
+	    {
+	      /* We've got an opaque type here.  */
+	      tree oty_name = DECL_NAME (sig_field);
+	      tree oty_type = lookup_field (rhstype, oty_name, 1, 1);
+
+	      if (oty_type == NULL_TREE || oty_type == error_mark_node)
+		{
+		  cp_error ("class `%T' does not contain type `%T'",
+			    rhstype, oty_type);
+		  undo_casts (sig_ty);
+		  return error_mark_node;
+		}
+	      oty_type = TREE_TYPE (oty_type);
+
+	      /* Cast `sig_field' to be of type `oty_type'.  This will be
+		 undone in `undo_casts' by walking over all the TYPE_DECLs.  */
+	      TREE_TYPE (sig_field_type) = TREE_TYPE (oty_type);
+	    }
+	  /* If we don't have an opaque type, we can ignore the `typedef'.  */
+	  continue;
+	}
+
+      /* Find the signature method corresponding to `sig_field'.  */
+      sig_method = DECL_MEMFUNC_POINTING_TO (sig_field);
+      sig_mname = DECL_NAME (sig_method);
+      sig_mtype = TREE_TYPE (sig_method);
+
+      basetype_path = TYPE_BINFO (rhstype);
+      baselink = lookup_fnfields (basetype_path, sig_mname, 0);
+      if (baselink == NULL_TREE || baselink == error_mark_node)
+	{
+	  if (! IS_DEFAULT_IMPLEMENTATION (sig_method))
+	    {
+	      cp_error ("class `%T' does not contain method `%s'",
+			rhstype, (int) IDENTIFIER_POINTER (sig_mname));
+	      undo_casts (sig_ty);
+	      return error_mark_node;
+	    }
+	  else
+	    {
+	      /* We use the signature's default implementation.  */
+	      rhs_method = sig_method;
+	    }
+	}
+      else
+	{
+	  /* Find the class method of the correct type.  */
+
+	  basetypes = TREE_PURPOSE (baselink);
+	  if (TREE_CODE (basetypes) == TREE_LIST)
+	    basetypes = TREE_VALUE (basetypes);
+
+	  rhs_method = TREE_VALUE (baselink);
+	  for (; rhs_method; rhs_method = TREE_CHAIN (rhs_method))
+	    if (sig_mname == DECL_NAME (rhs_method)
+		&& ! DECL_STATIC_FUNCTION_P (rhs_method)
+		&& match_method_types (sig_mtype, TREE_TYPE (rhs_method)))
+	      break;
+
+	  if (rhs_method == NULL_TREE
+	      || (compute_access (basetypes, rhs_method)
+		  != access_public))
+	    {
+	      error ("class `%s' does not contain a method conforming to `%s'",
+		     TYPE_NAME_STRING (rhstype),
+		     fndecl_as_string (NULL, sig_method, 1));
+	      undo_casts (sig_ty);
+	      return error_mark_node;
+	    }
+	}
+
+      if (sig_ptr_p && rhs_method != sig_method)
+	{
+	  tree rhs_field = DECL_MEMFUNC_POINTER_TO (rhs_method);
+
+	  if (first_rhs_field == NULL_TREE)
+	    {
+	      first_rhs_field = rhs_field;
+	      last_rhs_field = rhs_field;
+	    }
+	  else if (TREE_CHAIN (last_rhs_field) == rhs_field)
+	    last_rhs_field = rhs_field;
+	  else
+	    offset_p = 0;
+	  
+	  tbl_entry = build_component_ref (rhs, DECL_NAME (rhs_field),
+					   NULL_TREE, 1);
+	}
+      else
+	{
+	  tree code, offset, pfn;
+
+	  if (rhs_method == sig_method)
+	    {
+	      code = integer_two_node;
+	      offset = integer_zero_node;
+	      pfn = build_unary_op (ADDR_EXPR, rhs_method, 0);
+	      TREE_TYPE (pfn) = ptr_type_node;
+	      offset_p = 0;	/* we can't offset the rhs sig table */
+	    }
+	  else if (DECL_VINDEX (rhs_method))
+	    {
+	      code = integer_one_node;
+	      offset = DECL_VINDEX (rhs_method);
+	      pfn = null_pointer_node;
+	    }
+	  else
+	    {
+	      code = integer_zero_node;
+	      offset = integer_zero_node;
+	      pfn = build_unary_op (ADDR_EXPR, rhs_method, 0);
+	      TREE_TYPE (pfn) = ptr_type_node;
+	    }
+
+	  tbl_entry = tree_cons (NULL_TREE, code,
+				 tree_cons (NULL_TREE, offset,
+					    build_tree_list (NULL_TREE, pfn)));
+	  tbl_entry = build_nt (CONSTRUCTOR, NULL_TREE, tbl_entry);
+	  TREE_HAS_CONSTRUCTOR (tbl_entry) = 1;
+	  TREE_CONSTANT (tbl_entry) = 1;
+	}
+
+      /* Chain those function address expressions together.  */
+      if (result)
+	result = tree_cons (NULL_TREE, tbl_entry, result);
+      else
+	result = build_tree_list (NULL_TREE, tbl_entry);
+    }
+
+  if (result == NULL_TREE)
+    {
+      undo_casts (sig_ty);
+      return NULL_TREE;
+    }
+
+  if (offset_p)
+    {
+      if (first_rhs_field == TYPE_FIELDS (rhstype))
+	{
+	  undo_casts (sig_ty);
+	  return integer_zero_node;
+	}
+      else
+	{
+	  undo_casts (sig_ty);
+	  return build_component_ref (rhs, DECL_NAME (first_rhs_field),
+				      NULL_TREE, 0);
+	}
+    }
+
+  result = build_nt (CONSTRUCTOR, NULL_TREE, nreverse (result));
+  TREE_HAS_CONSTRUCTOR (result) = 1;
+  TREE_CONSTANT (result) = !sig_ptr_p;
+
+  undo_casts (sig_ty);
+  return result;
+}
+
+/* Build a signature table declaration and initialize it or return an
+   existing one if we built one already.  If we don't get a constructor
+   as initialization expression, we don't need a new signature table
+   variable and just hand back the init expression.
+
+   The declaration processing is done by hand instead of using `finish_decl'
+   so that we can make signature pointers global variables instead of
+   static ones.  */
+
+static tree
+build_sigtable (sig_type, rhs_type, init_from)
+     tree sig_type, rhs_type, init_from;
+{
+  tree name = NULL_TREE;
+  tree decl = NULL_TREE;
+  tree init_expr;
+
+  push_obstacks_nochange ();
+  end_temporary_allocation ();
+
+  if (! IS_SIGNATURE (rhs_type))
+    {
+      name = get_sigtable_name (sig_type, rhs_type);
+      decl = IDENTIFIER_GLOBAL_VALUE (name);
+    }
+  if (decl == NULL_TREE)
+    {
+      tree init;
+
+      /* We allow only one signature table to be generated for signatures
+	 with opaque types.  Otherwise we create a loophole in the type
+	 system since we could cast data from one classes implementation
+	 of the opaque type to that of another class.  */
+      if (SIGNATURE_HAS_OPAQUE_TYPEDECLS (sig_type)
+	  && SIGTABLE_HAS_BEEN_GENERATED (sig_type))
+	{
+	  error ("signature with opaque type implemented by multiple classes");
+	  return error_mark_node;
+	}
+      SIGTABLE_HAS_BEEN_GENERATED (sig_type) = 1;
+
+      init_expr = build_signature_table_constructor (sig_type, init_from);
+      if (TREE_CODE (init_expr) != CONSTRUCTOR)
+	return init_expr;
+
+      if (name == NULL_TREE)
+	name = get_sigtable_name (sig_type, rhs_type);
+      {
+	tree context = current_function_decl;
+
+	/* Make the signature table global, not just static in whichever
+	   function a signature pointer/ref is used for the first time.  */
+	current_function_decl = NULL_TREE;
+	decl = pushdecl_top_level (build_decl (VAR_DECL, name, sig_type));
+	current_function_decl = context;
+      }
+      IDENTIFIER_GLOBAL_VALUE (name) = decl;
+      store_init_value (decl, init_expr);
+      if (IS_SIGNATURE (rhs_type))
+	{
+	  init = DECL_INITIAL (decl);
+	  DECL_INITIAL (decl) = error_mark_node;
+	}
+
+      DECL_ALIGN (decl) = MAX (TYPE_ALIGN (double_type_node),
+			       DECL_ALIGN (decl));
+#if 0
+      /* GDB-4.7 doesn't find the initialization value of a signature table
+	 when it is constant.  */
+      TREE_READONLY (decl) = 1;
+#endif
+      TREE_STATIC (decl) = 1;
+      TREE_USED (decl) = 1;
+
+      make_decl_rtl (decl, NULL, 1);
+      if (IS_SIGNATURE (rhs_type))
+	expand_static_init (decl, init);
+    }
+
+  pop_obstacks ();
+
+  return decl;
+}
+
+/* Create a constructor or modify expression if the LHS of an assignment
+   is a signature pointer or a signature reference.  If LHS is a record
+   type node, we build a constructor, otherwise a compound expression.  */
+
+tree
+build_signature_pointer_constructor (lhs, rhs)
+     tree lhs, rhs;
+{
+  register struct obstack *ambient_obstack = current_obstack;
+  register struct obstack *ambient_saveable_obstack = saveable_obstack;
+  int initp = (TREE_CODE (lhs) == RECORD_TYPE);
+  tree lhstype = initp ? lhs : TREE_TYPE (lhs);
+  tree rhstype = TREE_TYPE (rhs);
+  tree sig_ty  = SIGNATURE_TYPE (lhstype);
+  tree sig_tbl, sptr_expr, optr_expr, vptr_expr;
+  tree result;
+
+  if (! ((TREE_CODE (rhstype) == POINTER_TYPE
+	  && TREE_CODE (TREE_TYPE (rhstype)) == RECORD_TYPE)
+	 || (TYPE_LANG_SPECIFIC (rhstype) &&
+	     (IS_SIGNATURE_POINTER (rhstype)
+	      || IS_SIGNATURE_REFERENCE (rhstype)))))
+    {
+      error ("invalid assignment to signature pointer or reference");
+      return error_mark_node;
+    }
+
+  /* If SIG_TY is permanent, make the signature table constructor and
+     the signature pointer/reference constructor permanent too.  */
+  if (TREE_PERMANENT (sig_ty))
+    {
+      current_obstack = &permanent_obstack;
+      saveable_obstack = &permanent_obstack;
+    }
+
+  if (TYPE_LANG_SPECIFIC (rhstype) &&
+      (IS_SIGNATURE_POINTER (rhstype) || IS_SIGNATURE_REFERENCE (rhstype)))
+    {
+      if (SIGNATURE_TYPE (rhstype) == sig_ty)
+	{
+	  /* LHS and RHS are signature pointers/refs of the same signature.  */
+	  optr_expr = build_optr_ref (rhs);
+	  sptr_expr = build_sptr_ref (rhs);
+	  vptr_expr = build_vptr_ref (rhs);
+	}
+      else
+	{
+	  /* We need to create a new signature table and copy
+	     elements from the rhs signature table.  */
+	  tree rhs_sptr_ref = build_sptr_ref (rhs);
+	  tree rhs_tbl = build1 (INDIRECT_REF, SIGNATURE_TYPE (rhstype),
+				 rhs_sptr_ref);
+
+	  sig_tbl = build_sigtable (sig_ty, SIGNATURE_TYPE (rhstype), rhs_tbl);
+	  if (sig_tbl == error_mark_node)
+	    return error_mark_node;
+
+	  optr_expr = build_optr_ref (rhs);
+	  if (sig_tbl == integer_zero_node)
+	    sptr_expr = rhs_sptr_ref;
+	  else
+	    sptr_expr = build_unary_op (ADDR_EXPR, sig_tbl, 0);
+	  TREE_TYPE (sptr_expr) = build_pointer_type (sig_ty);
+	  vptr_expr = build_vptr_ref (rhs);
+	}
+    }
+  else
+    {
+      tree rhs_vptr;
+
+      if (TYPE_USES_COMPLEX_INHERITANCE (TREE_TYPE (rhstype)))
+	{
+	  sorry ("class with multiple inheritance as implementation of signature");
+	  return error_mark_node;
+	}
+
+      sig_tbl = build_sigtable (sig_ty, TREE_TYPE (rhstype), rhs);
+      if (sig_tbl == error_mark_node)
+	return error_mark_node;
+
+      optr_expr = rhs;
+      sptr_expr = build_unary_op (ADDR_EXPR, sig_tbl, 0);
+      if (CLASSTYPE_VFIELD (TREE_TYPE (rhstype)))
+	{
+	  rhs_vptr = DECL_NAME (CLASSTYPE_VFIELD (TREE_TYPE (rhstype)));
+	  vptr_expr = build_component_ref (build_indirect_ref (rhs, 0),
+					   rhs_vptr, NULL_TREE, 0);
+	}
+      else
+	vptr_expr = null_pointer_node;
+      TREE_TYPE (vptr_expr) = build_pointer_type (vtbl_type_node);
+    }
+
+  if (initp)
+    {
+      result = tree_cons (NULL_TREE, optr_expr,
+			  tree_cons (NULL_TREE, sptr_expr,
+				     build_tree_list (NULL_TREE, vptr_expr)));
+      result = build_nt (CONSTRUCTOR, NULL_TREE, result);
+      TREE_HAS_CONSTRUCTOR (result) = 1;
+      result = digest_init (lhstype, result, 0);
+    }
+  else
+    {
+      if (TREE_READONLY (lhs) || TYPE_READONLY (lhstype))
+	  readonly_error (lhs, "assignment", 0);
+
+      optr_expr = build_modify_expr (build_optr_ref (lhs), NOP_EXPR,
+				     optr_expr);
+      sptr_expr = build_modify_expr (build_sptr_ref (lhs), NOP_EXPR,
+				     sptr_expr);
+      vptr_expr = build_modify_expr (build_vptr_ref (lhs), NOP_EXPR,
+				     vptr_expr);
+
+      result = tree_cons (NULL_TREE, optr_expr,
+			  tree_cons (NULL_TREE, sptr_expr,
+				     tree_cons (NULL_TREE, vptr_expr,
+						build_tree_list (NULL_TREE,
+								 lhs))));
+      result = build_compound_expr (result);
+    }
+
+  current_obstack = ambient_obstack;
+  saveable_obstack = ambient_saveable_obstack;
+  return result;
+}
+
+/* Build a temporary variable declaration for the instance of a signature
+   member function call if it isn't a declaration node already.  Simply
+   using a SAVE_EXPR doesn't work since we need `this' in both branches
+   of a conditional expression.  */
+
+static tree
+save_this (instance)
+     tree instance;
+{
+  tree decl;
+
+  if (TREE_CODE_CLASS (TREE_CODE (instance)) == 'd')
+    decl = instance;
+  else
+    {
+      decl = build_decl (VAR_DECL, NULL_TREE, TREE_TYPE (instance));
+      DECL_REGISTER (decl) = 1;
+      layout_decl (decl, 0);
+      expand_decl (decl);
+    }
+
+  return decl;
+}
+
+/* Build a signature member function call.  Looks up the signature table
+   entry corresponding to FUNCTION.  Depending on the value of the CODE
+   field, either call the function in PFN directly, or use OFFSET to
+   index INSTANCE's virtual function table.  */
+
+tree
+build_signature_method_call (basetype, instance, function, parms)
+     tree basetype, instance, function, parms;
+{
+  tree saved_instance = save_this (instance);	/* Create temp for `this'.  */
+  tree signature_tbl_ptr = build_sptr_ref (saved_instance);
+  tree sig_field_name = DECL_NAME (DECL_MEMFUNC_POINTER_TO (function));
+  tree basetype_path = TYPE_BINFO (basetype);
+  tree tbl_entry = build_component_ref (build1 (INDIRECT_REF, basetype,
+						signature_tbl_ptr),
+					sig_field_name, basetype_path, 1);
+  tree code, offset, pfn, vfn;
+  tree deflt_call = NULL_TREE, direct_call, virtual_call, result;
+
+  code = build_component_ref (tbl_entry, get_identifier (SIGTABLE_CODE_NAME),
+			     NULL_TREE, 1);
+  offset = build_component_ref (tbl_entry,
+				get_identifier (SIGTABLE_OFFSET_NAME),
+			     NULL_TREE, 1);
+  pfn = build_component_ref (tbl_entry, get_identifier (SIGTABLE_PFN_NAME),
+			     NULL_TREE, 1);
+  TREE_TYPE (pfn) = build_pointer_type (TREE_TYPE (function)); 
+
+  if (IS_DEFAULT_IMPLEMENTATION (function))
+    {
+      pfn = save_expr (pfn);
+      deflt_call = build_function_call (pfn,
+					tree_cons (NULL_TREE, saved_instance,
+						   TREE_CHAIN (parms)));
+    }
+
+  {
+    /* Cast the signature method to have `this' of a normal pointer type.  */
+    tree old_this = TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (TREE_TYPE (pfn))));
+
+    TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (TREE_TYPE (pfn)))) =
+      build_type_variant (TYPE_POINTER_TO (basetype),
+			  TYPE_READONLY (old_this),
+			  TYPE_VOLATILE (old_this));
+
+    direct_call = build_function_call (pfn, parms);
+
+    vfn = build_vfn_ref (&TREE_VALUE (parms), saved_instance, offset);
+    TREE_TYPE (vfn) = build_pointer_type (TREE_TYPE (function));
+    virtual_call = build_function_call (vfn, parms);
+
+    /* Undo the cast, make `this' a signature pointer again.  */
+    TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (TREE_TYPE (pfn)))) = old_this;
+  }
+
+  /* Once the function was found, there should be no reason why we
+     couldn't build the member function pointer call.  */
+  if (!direct_call || direct_call == error_mark_node
+      || !virtual_call || virtual_call == error_mark_node
+      || (IS_DEFAULT_IMPLEMENTATION (function)
+	  && (!deflt_call || deflt_call == error_mark_node)))
+    {
+      compiler_error ("cannot build call of signature member function `%s'",
+		      fndecl_as_string (NULL, function, 1));
+      return error_mark_node;
+    }
+
+  if (IS_DEFAULT_IMPLEMENTATION (function))
+    {
+      tree test = build_binary_op_nodefault (EQ_EXPR, code, integer_one_node,
+					     EQ_EXPR);
+      result = build_conditional_expr (code,
+				       build_conditional_expr (test,
+							       virtual_call,
+							       deflt_call),
+				       direct_call);
+    }
+  else
+    result = build_conditional_expr (code, virtual_call, direct_call);
+
+  /* If we created a temporary variable for `this', initialize it first.  */
+  if (instance != saved_instance)
+    result = build (COMPOUND_EXPR, TREE_TYPE (result),
+		    build_modify_expr (saved_instance, NOP_EXPR, instance),
+		    result);
+
+  return result;
+}
+
+/* Create a COMPONENT_REF expression for referencing the OPTR field
+   of a signature pointer or reference.  */
+
+tree
+build_optr_ref (instance)
+     tree instance;
+{
+  tree field = get_identifier (SIGNATURE_OPTR_NAME);
+
+  return build_component_ref (instance, field, NULL_TREE, 1);
+}
+
+/* Create a COMPONENT_REF expression for referencing the SPTR field
+   of a signature pointer or reference.  */
+
+tree
+build_sptr_ref (instance)
+     tree instance;
+{
+  tree field = get_identifier (SIGNATURE_SPTR_NAME);
+
+  return build_component_ref (instance, field, NULL_TREE, 1);
+}
+
+/* Create a COMPONENT_REF expression for referencing the VPTR field
+   of a signature pointer or reference.  */
+
+tree
+build_vptr_ref (instance)
+     tree instance;
+{
+  tree field = get_identifier (SIGNATURE_VPTR_NAME);
+
+  return build_component_ref (instance, field, NULL_TREE, 1);
+}