gcc/cp/cvt.c

   1 /* Language-level data type conversion for GNU C++.
   2    Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   3    1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   4    Hacked by Michael Tiemann (tiemann@cygnus.com)
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 2, or (at your option)
  11 any later version.
  12
  13 GCC is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING.  If not, write to
  20 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  21 Boston, MA 02110-1301, USA.  */
  22
  23
  24 /* This file contains the functions for converting C++ expressions
  25    to different data types.  The only entry point is `convert'.
  26    Every language front end must have a `convert' function
  27    but what kind of conversions it does will depend on the language.  */
  28
  29 #include "config.h"
  30 #include "system.h"
  31 #include "coretypes.h"
  32 #include "tm.h"
  33 #include "tree.h"
  34 #include "flags.h"
  35 #include "cp-tree.h"
  36 #include "convert.h"
  37 #include "toplev.h"
  38 #include "decl.h"
  39 #include "target.h"
  40
  41 static tree cp_convert_to_pointer (tree, tree, bool);
  42 static tree convert_to_pointer_force (tree, tree);
  43 static tree build_type_conversion (tree, tree);
  44 static tree build_up_reference (tree, tree, int, tree);
  45 static void warn_ref_binding (tree, tree, tree);
  46
  47 /* Change of width--truncation and extension of integers or reals--
  48    is represented with NOP_EXPR.  Proper functioning of many things
  49    assumes that no other conversions can be NOP_EXPRs.
  50
  51    Conversion between integer and pointer is represented with CONVERT_EXPR.
  52    Converting integer to real uses FLOAT_EXPR
  53    and real to integer uses FIX_TRUNC_EXPR.
  54
  55    Here is a list of all the functions that assume that widening and
  56    narrowing is always done with a NOP_EXPR:
  57      In convert.c, convert_to_integer.
  58      In c-typeck.c, build_binary_op_nodefault (boolean ops),
  59         and c_common_truthvalue_conversion.
  60      In expr.c: expand_expr, for operands of a MULT_EXPR.
  61      In fold-const.c: fold.
  62      In tree.c: get_narrower and get_unwidened.
  63
  64    C++: in multiple-inheritance, converting between pointers may involve
  65    adjusting them by a delta stored within the class definition.  */
  66 \f
  67 /* Subroutines of `convert'.  */
  68
  69 /* if converting pointer to pointer
  70      if dealing with classes, check for derived->base or vice versa
  71      else if dealing with method pointers, delegate
  72      else convert blindly
  73    else if converting class, pass off to build_type_conversion
  74    else try C-style pointer conversion.  If FORCE is true then allow
  75    conversions via virtual bases (these are permitted by reinterpret_cast,
  76    but not static_cast).  */
  77
  78 static tree
  79 cp_convert_to_pointer (tree type, tree expr, bool force)
  80 {
  81   tree intype = TREE_TYPE (expr);
  82   enum tree_code form;
  83   tree rval;
  84   if (intype == error_mark_node)
  85     return error_mark_node;
  86
  87   if (IS_AGGR_TYPE (intype))
  88     {
  89       intype = complete_type (intype);
  90       if (!COMPLETE_TYPE_P (intype))
  91         {
  92           error ("can't convert from incomplete type %qT to %qT",
  93                  intype, type);
  94           return error_mark_node;
  95         }
  96
  97       rval = build_type_conversion (type, expr);
  98       if (rval)
  99         {
 100           if (rval == error_mark_node)
 101             error ("conversion of %qE from %qT to %qT is ambiguous",
 102                    expr, intype, type);
 103           return rval;
 104         }
 105     }
 106
 107   /* Handle anachronistic conversions from (::*)() to cv void* or (*)().  */
 108   if (TREE_CODE (type) == POINTER_TYPE
 109       && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE
 110           || VOID_TYPE_P (TREE_TYPE (type))))
 111     {
 112       if (TYPE_PTRMEMFUNC_P (intype)
 113           || TREE_CODE (intype) == METHOD_TYPE)
 114         return convert_member_func_to_ptr (type, expr);
 115       if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE)
 116         return build_nop (type, expr);
 117       intype = TREE_TYPE (expr);
 118     }
 119
 120   if (expr == error_mark_node)
 121     return error_mark_node;
 122
 123   form = TREE_CODE (intype);
 124
 125   if (POINTER_TYPE_P (intype))
 126     {
 127       intype = TYPE_MAIN_VARIANT (intype);
 128
 129       if (TYPE_MAIN_VARIANT (type) != intype
 130           && TREE_CODE (type) == POINTER_TYPE
 131           && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
 132           && IS_AGGR_TYPE (TREE_TYPE (type))
 133           && IS_AGGR_TYPE (TREE_TYPE (intype))
 134           && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
 135         {
 136           enum tree_code code = PLUS_EXPR;
 137           tree binfo;
 138           tree intype_class;
 139           tree type_class;
 140           bool same_p;
 141
 142           intype_class = TREE_TYPE (intype);
 143           type_class = TREE_TYPE (type);
 144
 145           same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class),
 146                                 TYPE_MAIN_VARIANT (type_class));
 147           binfo = NULL_TREE;
 148           /* Try derived to base conversion.  */
 149           if (!same_p)
 150             binfo = lookup_base (intype_class, type_class, ba_check, NULL);
 151           if (!same_p && !binfo)
 152             {
 153               /* Try base to derived conversion.  */
 154               binfo = lookup_base (type_class, intype_class, ba_check, NULL);
 155               code = MINUS_EXPR;
 156             }
 157           if (binfo == error_mark_node)
 158             return error_mark_node;
 159           if (binfo || same_p)
 160             {
 161               if (binfo)
 162                 expr = build_base_path (code, expr, binfo, 0);
 163               /* Add any qualifier conversions.  */
 164               return build_nop (type, expr);
 165             }
 166         }
 167
 168       if (TYPE_PTRMEMFUNC_P (type))
 169         {
 170           error ("cannot convert %qE from type %qT to type %qT",
 171                  expr, intype, type);
 172           return error_mark_node;
 173         }
 174
 175       return build_nop (type, expr);
 176     }
 177   else if (TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))
 178     {
 179       tree b1;
 180       tree b2;
 181       tree binfo;
 182       enum tree_code code = PLUS_EXPR;
 183       base_kind bk;
 184
 185       b1 = TYPE_PTRMEM_CLASS_TYPE (type);
 186       b2 = TYPE_PTRMEM_CLASS_TYPE (intype);
 187       binfo = lookup_base (b1, b2, ba_check, &bk);
 188       if (!binfo)
 189         {
 190           binfo = lookup_base (b2, b1, ba_check, &bk);
 191           code = MINUS_EXPR;
 192         }
 193       if (binfo == error_mark_node)
 194         return error_mark_node;
 195
 196       if (bk == bk_via_virtual)
 197         {
 198           if (force)
 199             warning (0, "pointer to member cast from %qT to %qT is via"
 200                      " virtual base", intype, type);
 201           else
 202             {
 203               error ("pointer to member cast from %qT to %qT is"
 204                      " via virtual base", intype, type);
 205               return error_mark_node;
 206             }
 207           /* This is a reinterpret cast, whose result is unspecified.
 208              We choose to do nothing.  */
 209           return build1 (NOP_EXPR, type, expr);
 210         }
 211
 212       if (TREE_CODE (expr) == PTRMEM_CST)
 213         expr = cplus_expand_constant (expr);
 214
 215       if (binfo && !integer_zerop (BINFO_OFFSET (binfo)))
 216         expr = size_binop (code,
 217                            build_nop (sizetype, expr),
 218                            BINFO_OFFSET (binfo));
 219       return build_nop (type, expr);
 220     }
 221   else if (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype))
 222     return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
 223                              /*c_cast_p=*/false);
 224   else if (TYPE_PTRMEMFUNC_P (intype))
 225     {
 226       if (!warn_pmf2ptr)
 227         {
 228           if (TREE_CODE (expr) == PTRMEM_CST)
 229             return cp_convert_to_pointer (type,
 230                                           PTRMEM_CST_MEMBER (expr),
 231                                           force);
 232           else if (TREE_CODE (expr) == OFFSET_REF)
 233             {
 234               tree object = TREE_OPERAND (expr, 0);
 235               return get_member_function_from_ptrfunc (&object,
 236                                                        TREE_OPERAND (expr, 1));
 237             }
 238         }
 239       error ("cannot convert %qE from type %qT to type %qT",
 240              expr, intype, type);
 241       return error_mark_node;
 242     }
 243
 244   if (integer_zerop (expr))
 245     {
 246       if (TYPE_PTRMEMFUNC_P (type))
 247         return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0,
 248                                  /*c_cast_p=*/false);
 249
 250       if (TYPE_PTRMEM_P (type))
 251         {
 252           /* A NULL pointer-to-member is represented by -1, not by
 253              zero.  */
 254           expr = build_int_cst_type (type, -1);
 255         }
 256       else
 257         expr = build_int_cst (type, 0);
 258
 259       return expr;
 260     }
 261   else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form))
 262     {
 263       error ("invalid conversion from %qT to %qT", intype, type);
 264       return error_mark_node;
 265     }
 266
 267   if (INTEGRAL_CODE_P (form))
 268     {
 269       if (TYPE_PRECISION (intype) == POINTER_SIZE)
 270         return build1 (CONVERT_EXPR, type, expr);
 271       expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
 272       /* Modes may be different but sizes should be the same.  There
 273          is supposed to be some integral type that is the same width
 274          as a pointer.  */
 275       gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
 276                   == GET_MODE_SIZE (TYPE_MODE (type)));
 277
 278       return convert_to_pointer (type, expr);
 279     }
 280
 281   if (type_unknown_p (expr))
 282     return instantiate_type (type, expr, tf_warning_or_error);
 283
 284   error ("cannot convert %qE from type %qT to type %qT",
 285          expr, intype, type);
 286   return error_mark_node;
 287 }
 288
 289 /* Like convert, except permit conversions to take place which
 290    are not normally allowed due to access restrictions
 291    (such as conversion from sub-type to private super-type).  */
 292
 293 static tree
 294 convert_to_pointer_force (tree type, tree expr)
 295 {
 296   tree intype = TREE_TYPE (expr);
 297   enum tree_code form = TREE_CODE (intype);
 298
 299   if (form == POINTER_TYPE)
 300     {
 301       intype = TYPE_MAIN_VARIANT (intype);
 302
 303       if (TYPE_MAIN_VARIANT (type) != intype
 304           && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE
 305           && IS_AGGR_TYPE (TREE_TYPE (type))
 306           && IS_AGGR_TYPE (TREE_TYPE (intype))
 307           && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE)
 308         {
 309           enum tree_code code = PLUS_EXPR;
 310           tree binfo;
 311
 312           binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type),
 313                                ba_unique, NULL);
 314           if (!binfo)
 315             {
 316               binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
 317                                    ba_unique, NULL);
 318               code = MINUS_EXPR;
 319             }
 320           if (binfo == error_mark_node)
 321             return error_mark_node;
 322           if (binfo)
 323             {
 324               expr = build_base_path (code, expr, binfo, 0);
 325               if (expr == error_mark_node)
 326                  return error_mark_node;
 327               /* Add any qualifier conversions.  */
 328               if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)),
 329                                 TREE_TYPE (type)))
 330                 expr = build_nop (type, expr);
 331               return expr;
 332             }
 333         }
 334     }
 335
 336   return cp_convert_to_pointer (type, expr, true);
 337 }
 338
 339 /* We are passing something to a function which requires a reference.
 340    The type we are interested in is in TYPE. The initial
 341    value we have to begin with is in ARG.
 342
 343    FLAGS controls how we manage access checking.
 344    DIRECT_BIND in FLAGS controls how any temporaries are generated.
 345      If DIRECT_BIND is set, DECL is the reference we're binding to.  */
 346
 347 static tree
 348 build_up_reference (tree type, tree arg, int flags, tree decl)
 349 {
 350   tree rval;
 351   tree argtype = TREE_TYPE (arg);
 352   tree target_type = TREE_TYPE (type);
 353
 354   gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
 355
 356   if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg))
 357     {
 358       /* Create a new temporary variable.  We can't just use a TARGET_EXPR
 359          here because it needs to live as long as DECL.  */
 360       tree targ = arg;
 361
 362       arg = make_temporary_var_for_ref_to_temp (decl, TREE_TYPE (arg));
 363
 364       /* Process the initializer for the declaration.  */
 365       DECL_INITIAL (arg) = targ;
 366       cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE,
 367                       LOOKUP_ONLYCONVERTING|DIRECT_BIND);
 368     }
 369   else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg))
 370     return get_target_expr (arg);
 371
 372   /* If we had a way to wrap this up, and say, if we ever needed its
 373      address, transform all occurrences of the register, into a memory
 374      reference we could win better.  */
 375   rval = build_unary_op (ADDR_EXPR, arg, 1);
 376   if (rval == error_mark_node)
 377     return error_mark_node;
 378
 379   if ((flags & LOOKUP_PROTECT)
 380       && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type)
 381       && IS_AGGR_TYPE (argtype)
 382       && IS_AGGR_TYPE (target_type))
 383     {
 384       /* We go through lookup_base for the access control.  */
 385       tree binfo = lookup_base (argtype, target_type, ba_check, NULL);
 386       if (binfo == error_mark_node)
 387         return error_mark_node;
 388       if (binfo == NULL_TREE)
 389         return error_not_base_type (target_type, argtype);
 390       rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
 391     }
 392   else
 393     rval
 394       = convert_to_pointer_force (build_pointer_type (target_type), rval);
 395   return build_nop (type, rval);
 396 }
 397
 398 /* Subroutine of convert_to_reference. REFTYPE is the target reference type.
 399    INTYPE is the original rvalue type and DECL is an optional _DECL node
 400    for diagnostics.
 401
 402    [dcl.init.ref] says that if an rvalue is used to
 403    initialize a reference, then the reference must be to a
 404    non-volatile const type.  */
 405
 406 static void
 407 warn_ref_binding (tree reftype, tree intype, tree decl)
 408 {
 409   tree ttl = TREE_TYPE (reftype);
 410
 411   if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl))
 412     {
 413       const char *msg;
 414
 415       if (CP_TYPE_VOLATILE_P (ttl) && decl)
 416           msg = "initialization of volatile reference type %q#T from"
 417             " rvalue of type %qT";
 418       else if (CP_TYPE_VOLATILE_P (ttl))
 419           msg = "conversion to volatile reference type %q#T "
 420             " from rvalue of type %qT";
 421       else if (decl)
 422           msg = "initialization of non-const reference type %q#T from"
 423             " rvalue of type %qT";
 424       else
 425           msg = "conversion to non-const reference type %q#T from"
 426             " rvalue of type %qT";
 427
 428       pedwarn (msg, reftype, intype);
 429     }
 430 }
 431
 432 /* For C++: Only need to do one-level references, but cannot
 433    get tripped up on signed/unsigned differences.
 434
 435    DECL is either NULL_TREE or the _DECL node for a reference that is being
 436    initialized.  It can be error_mark_node if we don't know the _DECL but
 437    we know it's an initialization.  */
 438
 439 tree
 440 convert_to_reference (tree reftype, tree expr, int convtype,
 441                       int flags, tree decl)
 442 {
 443   tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype));
 444   tree intype;
 445   tree rval = NULL_TREE;
 446   tree rval_as_conversion = NULL_TREE;
 447   bool can_convert_intype_to_type;
 448
 449   if (TREE_CODE (type) == FUNCTION_TYPE
 450       && TREE_TYPE (expr) == unknown_type_node)
 451     expr = instantiate_type (type, expr,
 452                              (flags & LOOKUP_COMPLAIN)
 453                              ? tf_warning_or_error : tf_none);
 454
 455   if (expr == error_mark_node)
 456     return error_mark_node;
 457
 458   intype = TREE_TYPE (expr);
 459
 460   gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE);
 461   gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE);
 462
 463   intype = TYPE_MAIN_VARIANT (intype);
 464
 465   can_convert_intype_to_type = can_convert (type, intype);
 466   if (!can_convert_intype_to_type
 467       && (convtype & CONV_IMPLICIT) && IS_AGGR_TYPE (intype)
 468       && ! (flags & LOOKUP_NO_CONVERSION))
 469     {
 470       /* Look for a user-defined conversion to lvalue that we can use.  */
 471
 472       rval_as_conversion
 473         = build_type_conversion (reftype, expr);
 474
 475       if (rval_as_conversion && rval_as_conversion != error_mark_node
 476           && real_lvalue_p (rval_as_conversion))
 477         {
 478           expr = rval_as_conversion;
 479           rval_as_conversion = NULL_TREE;
 480           intype = type;
 481           can_convert_intype_to_type = 1;
 482         }
 483     }
 484
 485   if (((convtype & CONV_STATIC) && can_convert (intype, type))
 486       || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type))
 487     {
 488       if (flags & LOOKUP_COMPLAIN)
 489         {
 490           tree ttl = TREE_TYPE (reftype);
 491           tree ttr = lvalue_type (expr);
 492
 493           if (! real_lvalue_p (expr))
 494             warn_ref_binding (reftype, intype, decl);
 495
 496           if (! (convtype & CONV_CONST)
 497                    && !at_least_as_qualified_p (ttl, ttr))
 498             pedwarn ("conversion from %qT to %qT discards qualifiers",
 499                      ttr, reftype);
 500         }
 501
 502       return build_up_reference (reftype, expr, flags, decl);
 503     }
 504   else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr))
 505     {
 506       /* When casting an lvalue to a reference type, just convert into
 507          a pointer to the new type and deference it.  This is allowed
 508          by San Diego WP section 5.2.9 paragraph 12, though perhaps it
 509          should be done directly (jason).  (int &)ri ---> *(int*)&ri */
 510
 511       /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they
 512          meant.  */
 513       if (TREE_CODE (intype) == POINTER_TYPE
 514           && (comptypes (TREE_TYPE (intype), type,
 515                          COMPARE_BASE | COMPARE_DERIVED)))
 516         warning (0, "casting %qT to %qT does not dereference pointer",
 517                  intype, reftype);
 518
 519       rval = build_unary_op (ADDR_EXPR, expr, 0);
 520       if (rval != error_mark_node)
 521         rval = convert_force (build_pointer_type (TREE_TYPE (reftype)),
 522                               rval, 0);
 523       if (rval != error_mark_node)
 524         rval = build1 (NOP_EXPR, reftype, rval);
 525     }
 526   else
 527     {
 528       rval = convert_for_initialization (NULL_TREE, type, expr, flags,
 529                                          "converting", 0, 0);
 530       if (rval == NULL_TREE || rval == error_mark_node)
 531         return rval;
 532       warn_ref_binding (reftype, intype, decl);
 533       rval = build_up_reference (reftype, rval, flags, decl);
 534     }
 535
 536   if (rval)
 537     {
 538       /* If we found a way to convert earlier, then use it.  */
 539       return rval;
 540     }
 541
 542   if (flags & LOOKUP_COMPLAIN)
 543     error ("cannot convert type %qT to type %qT", intype, reftype);
 544
 545   return error_mark_node;
 546 }
 547
 548 /* We are using a reference VAL for its value. Bash that reference all the
 549    way down to its lowest form.  */
 550
 551 tree
 552 convert_from_reference (tree val)
 553 {
 554   if (TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE)
 555     {
 556       tree t = canonical_type_variant (TREE_TYPE (TREE_TYPE (val)));
 557       tree ref = build1 (INDIRECT_REF, t, val);
 558
 559        /* We *must* set TREE_READONLY when dereferencing a pointer to const,
 560           so that we get the proper error message if the result is used
 561           to assign to.  Also, &* is supposed to be a no-op.  */
 562       TREE_READONLY (ref) = CP_TYPE_CONST_P (t);
 563       TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t);
 564       TREE_SIDE_EFFECTS (ref)
 565         = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val));
 566       REFERENCE_REF_P (ref) = 1;
 567       val = ref;
 568     }
 569
 570   return val;
 571 }
 572
 573 /* Really perform an lvalue-to-rvalue conversion, including copying an
 574    argument of class type into a temporary.  */
 575
 576 tree
 577 force_rvalue (tree expr)
 578 {
 579   if (IS_AGGR_TYPE (TREE_TYPE (expr)) && TREE_CODE (expr) != TARGET_EXPR)
 580     expr = ocp_convert (TREE_TYPE (expr), expr,
 581                         CONV_IMPLICIT|CONV_FORCE_TEMP, LOOKUP_NORMAL);
 582   else
 583     expr = decay_conversion (expr);
 584
 585   return expr;
 586 }
 587 \f
 588 /* C++ conversions, preference to static cast conversions.  */
 589
 590 tree
 591 cp_convert (tree type, tree expr)
 592 {
 593   return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL);
 594 }
 595
 596 /* Conversion...
 597
 598    FLAGS indicates how we should behave.  */
 599
 600 tree
 601 ocp_convert (tree type, tree expr, int convtype, int flags)
 602 {
 603   tree e = expr;
 604   enum tree_code code = TREE_CODE (type);
 605   const char *invalid_conv_diag;
 606
 607   if (error_operand_p (e) || type == error_mark_node)
 608     return error_mark_node;
 609
 610   complete_type (type);
 611   complete_type (TREE_TYPE (expr));
 612
 613   if ((invalid_conv_diag
 614        = targetm.invalid_conversion (TREE_TYPE (expr), type)))
 615     {
 616       error (invalid_conv_diag);
 617       return error_mark_node;
 618     }
 619
 620   e = integral_constant_value (e);
 621
 622   if (IS_AGGR_TYPE (type) && (convtype & CONV_FORCE_TEMP)
 623       /* Some internal structures (vtable_entry_type, sigtbl_ptr_type)
 624          don't go through finish_struct, so they don't have the synthesized
 625          constructors.  So don't force a temporary.  */
 626       && TYPE_HAS_CONSTRUCTOR (type))
 627     /* We need a new temporary; don't take this shortcut.  */;
 628   else if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (e)))
 629     {
 630       if (same_type_p (type, TREE_TYPE (e)))
 631         /* The call to fold will not always remove the NOP_EXPR as
 632            might be expected, since if one of the types is a typedef;
 633            the comparison in fold is just equality of pointers, not a
 634            call to comptypes.  We don't call fold in this case because
 635            that can result in infinite recursion; fold will call
 636            convert, which will call ocp_convert, etc.  */
 637         return e;
 638       /* For complex data types, we need to perform componentwise
 639          conversion.  */
 640       else if (TREE_CODE (type) == COMPLEX_TYPE)
 641         return fold_if_not_in_template (convert_to_complex (type, e));
 642       else if (TREE_CODE (e) == TARGET_EXPR)
 643         {
 644           /* Don't build a NOP_EXPR of class type.  Instead, change the
 645              type of the temporary.  Only allow this for cv-qual changes,
 646              though.  */
 647           gcc_assert (same_type_p (TYPE_MAIN_VARIANT (TREE_TYPE (e)),
 648                                    TYPE_MAIN_VARIANT (type)));
 649           TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type;
 650           return e;
 651         }
 652       else
 653         {
 654           /* We shouldn't be treating objects of ADDRESSABLE type as
 655              rvalues.  */
 656           gcc_assert (!TREE_ADDRESSABLE (type));
 657           return fold_if_not_in_template (build_nop (type, e));
 658         }
 659     }
 660
 661   if (code == VOID_TYPE && (convtype & CONV_STATIC))
 662     {
 663       e = convert_to_void (e, /*implicit=*/NULL);
 664       return e;
 665     }
 666
 667   if (INTEGRAL_CODE_P (code))
 668     {
 669       tree intype = TREE_TYPE (e);
 670       /* enum = enum, enum = int, enum = float, (enum)pointer are all
 671          errors.  */
 672       if (TREE_CODE (type) == ENUMERAL_TYPE
 673           && (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype)
 674                 || TREE_CODE (intype) == REAL_TYPE)
 675                && ! (convtype & CONV_STATIC))
 676               || TREE_CODE (intype) == POINTER_TYPE))
 677         {
 678           if (flags & LOOKUP_COMPLAIN)
 679             pedwarn ("conversion from %q#T to %q#T", intype, type);
 680
 681           if (flag_pedantic_errors)
 682             return error_mark_node;
 683         }
 684       if (IS_AGGR_TYPE (intype))
 685         {
 686           tree rval;
 687           rval = build_type_conversion (type, e);
 688           if (rval)
 689             return rval;
 690           if (flags & LOOKUP_COMPLAIN)
 691             error ("%q#T used where a %qT was expected", intype, type);
 692           return error_mark_node;
 693         }
 694       if (code == BOOLEAN_TYPE)
 695         return cp_truthvalue_conversion (e);
 696
 697       return fold_if_not_in_template (convert_to_integer (type, e));
 698     }
 699   if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type))
 700     return fold_if_not_in_template (cp_convert_to_pointer (type, e, false));
 701   if (code == VECTOR_TYPE)
 702     {
 703       tree in_vtype = TREE_TYPE (e);
 704       if (IS_AGGR_TYPE (in_vtype))
 705         {
 706           tree ret_val;
 707           ret_val = build_type_conversion (type, e);
 708           if (ret_val)
 709             return ret_val;
 710           if (flags & LOOKUP_COMPLAIN)
 711             error ("%q#T used where a %qT was expected", in_vtype, type);
 712           return error_mark_node;
 713         }
 714       return fold_if_not_in_template (convert_to_vector (type, e));
 715     }
 716   if (code == REAL_TYPE || code == COMPLEX_TYPE)
 717     {
 718       if (IS_AGGR_TYPE (TREE_TYPE (e)))
 719         {
 720           tree rval;
 721           rval = build_type_conversion (type, e);
 722           if (rval)
 723             return rval;
 724           else
 725             if (flags & LOOKUP_COMPLAIN)
 726               error ("%q#T used where a floating point value was expected",
 727                         TREE_TYPE (e));
 728         }
 729       if (code == REAL_TYPE)
 730         return fold_if_not_in_template (convert_to_real (type, e));
 731       else if (code == COMPLEX_TYPE)
 732         return fold_if_not_in_template (convert_to_complex (type, e));
 733     }
 734
 735   /* New C++ semantics:  since assignment is now based on
 736      memberwise copying,  if the rhs type is derived from the
 737      lhs type, then we may still do a conversion.  */
 738   if (IS_AGGR_TYPE_CODE (code))
 739     {
 740       tree dtype = TREE_TYPE (e);
 741       tree ctor = NULL_TREE;
 742
 743       dtype = TYPE_MAIN_VARIANT (dtype);
 744
 745       /* Conversion between aggregate types.  New C++ semantics allow
 746          objects of derived type to be cast to objects of base type.
 747          Old semantics only allowed this between pointers.
 748
 749          There may be some ambiguity between using a constructor
 750          vs. using a type conversion operator when both apply.  */
 751
 752       ctor = e;
 753
 754       if (abstract_virtuals_error (NULL_TREE, type))
 755         return error_mark_node;
 756
 757       if ((flags & LOOKUP_ONLYCONVERTING)
 758           && ! (IS_AGGR_TYPE (dtype) && DERIVED_FROM_P (type, dtype)))
 759         /* For copy-initialization, first we create a temp of the proper type
 760            with a user-defined conversion sequence, then we direct-initialize
 761            the target with the temp (see [dcl.init]).  */
 762         ctor = build_user_type_conversion (type, ctor, flags);
 763       else
 764         ctor = build_special_member_call (NULL_TREE,
 765                                           complete_ctor_identifier,
 766                                           build_tree_list (NULL_TREE, ctor),
 767                                           type, flags);
 768       if (ctor)
 769         return build_cplus_new (type, ctor);
 770     }
 771
 772   if (flags & LOOKUP_COMPLAIN)
 773     error ("conversion from %qT to non-scalar type %qT requested",
 774            TREE_TYPE (expr), type);
 775   return error_mark_node;
 776 }
 777
 778 /* When an expression is used in a void context, its value is discarded and
 779    no lvalue-rvalue and similar conversions happen [expr.static.cast/4,
 780    stmt.expr/1, expr.comma/1].  This permits dereferencing an incomplete type
 781    in a void context. The C++ standard does not define what an `access' to an
 782    object is, but there is reason to believe that it is the lvalue to rvalue
 783    conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it
 784    accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8
 785    indicates that volatile semantics should be the same between C and C++
 786    where ever possible. C leaves it implementation defined as to what
 787    constitutes an access to a volatile. So, we interpret `*vp' as a read of
 788    the volatile object `vp' points to, unless that is an incomplete type. For
 789    volatile references we do not do this interpretation, because that would
 790    make it impossible to ignore the reference return value from functions. We
 791    issue warnings in the confusing cases.
 792
 793    IMPLICIT is tells us the context of an implicit void conversion.  */
 794
 795 tree
 796 convert_to_void (tree expr, const char *implicit)
 797 {
 798   if (expr == error_mark_node
 799       || TREE_TYPE (expr) == error_mark_node)
 800     return error_mark_node;
 801   if (!TREE_TYPE (expr))
 802     return expr;
 803   if (invalid_nonstatic_memfn_p (expr))
 804     return error_mark_node;
 805   if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR)
 806     {
 807       error ("pseudo-destructor is not called");
 808       return error_mark_node;
 809     }
 810   if (VOID_TYPE_P (TREE_TYPE (expr)))
 811     return expr;
 812   switch (TREE_CODE (expr))
 813     {
 814     case COND_EXPR:
 815       {
 816         /* The two parts of a cond expr might be separate lvalues.  */
 817         tree op1 = TREE_OPERAND (expr,1);
 818         tree op2 = TREE_OPERAND (expr,2);
 819         tree new_op1 = convert_to_void
 820           (op1, (implicit && !TREE_SIDE_EFFECTS (op2)
 821                  ? "second operand of conditional" : NULL));
 822         tree new_op2 = convert_to_void
 823           (op2, (implicit && !TREE_SIDE_EFFECTS (op1)
 824                  ? "third operand of conditional" : NULL));
 825
 826         expr = build3 (COND_EXPR, TREE_TYPE (new_op1),
 827                        TREE_OPERAND (expr, 0), new_op1, new_op2);
 828         break;
 829       }
 830
 831     case COMPOUND_EXPR:
 832       {
 833         /* The second part of a compound expr contains the value.  */
 834         tree op1 = TREE_OPERAND (expr,1);
 835         tree new_op1 = convert_to_void
 836           (op1, (implicit && !TREE_NO_WARNING (expr)
 837                  ? "right-hand operand of comma" : NULL));
 838
 839         if (new_op1 != op1)
 840           {
 841             tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1),
 842                              TREE_OPERAND (expr, 0), new_op1);
 843             expr = t;
 844           }
 845
 846         break;
 847       }
 848
 849     case NON_LVALUE_EXPR:
 850     case NOP_EXPR:
 851       /* These have already decayed to rvalue.  */
 852       break;
 853
 854     case CALL_EXPR:   /* We have a special meaning for volatile void fn().  */
 855       break;
 856
 857     case INDIRECT_REF:
 858       {
 859         tree type = TREE_TYPE (expr);
 860         int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0)))
 861                            == REFERENCE_TYPE;
 862         int is_volatile = TYPE_VOLATILE (type);
 863         int is_complete = COMPLETE_TYPE_P (complete_type (type));
 864
 865         /* Can't load the value if we don't know the type.  */
 866         if (is_volatile && !is_complete)
 867           warning (0, "object of incomplete type %qT will not be accessed in %s",
 868                    type, implicit ? implicit : "void context");
 869         /* Don't load the value if this is an implicit dereference, or if
 870            the type needs to be handled by ctors/dtors.  */
 871         else if (is_volatile && (is_reference || TREE_ADDRESSABLE (type)))
 872           warning (0, "object of type %qT will not be accessed in %s",
 873                    TREE_TYPE (TREE_OPERAND (expr, 0)),
 874                    implicit ? implicit : "void context");
 875         if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type))
 876           expr = TREE_OPERAND (expr, 0);
 877
 878         break;
 879       }
 880
 881     case VAR_DECL:
 882       {
 883         /* External variables might be incomplete.  */
 884         tree type = TREE_TYPE (expr);
 885         int is_complete = COMPLETE_TYPE_P (complete_type (type));
 886
 887         if (TYPE_VOLATILE (type) && !is_complete)
 888           warning (0, "object %qE of incomplete type %qT will not be accessed in %s",
 889                    expr, type, implicit ? implicit : "void context");
 890         break;
 891       }
 892
 893     case TARGET_EXPR:
 894       /* Don't bother with the temporary object returned from a function if
 895          we don't use it and don't need to destroy it.  We'll still
 896          allocate space for it in expand_call or declare_return_variable,
 897          but we don't need to track it through all the tree phases.  */
 898       if (TARGET_EXPR_IMPLICIT_P (expr)
 899           && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr)))
 900         {
 901           tree init = TARGET_EXPR_INITIAL (expr);
 902           if (TREE_CODE (init) == AGGR_INIT_EXPR
 903               && !AGGR_INIT_VIA_CTOR_P (init))
 904             {
 905               tree fn = TREE_OPERAND (init, 0);
 906               expr = build3 (CALL_EXPR, TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))),
 907                              fn, TREE_OPERAND (init, 1), NULL_TREE);
 908             }
 909         }
 910       break;
 911
 912     default:;
 913     }
 914   {
 915     tree probe = expr;
 916
 917     if (TREE_CODE (probe) == ADDR_EXPR)
 918       probe = TREE_OPERAND (expr, 0);
 919     if (type_unknown_p (probe))
 920       {
 921         /* [over.over] enumerates the places where we can take the address
 922            of an overloaded function, and this is not one of them.  */
 923         pedwarn ("%s cannot resolve address of overloaded function",
 924                     implicit ? implicit : "void cast");
 925         expr = void_zero_node;
 926       }
 927     else if (implicit && probe == expr && is_overloaded_fn (probe))
 928       {
 929         /* Only warn when there is no &.  */
 930         warning (0, "%s is a reference, not call, to function %qE",
 931                  implicit, expr);
 932         if (TREE_CODE (expr) == COMPONENT_REF)
 933           expr = TREE_OPERAND (expr, 0);
 934       }
 935   }
 936
 937   if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr)))
 938     {
 939       if (implicit
 940           && warn_unused_value
 941           && !TREE_NO_WARNING (expr)
 942           && !processing_template_decl)
 943         {
 944           /* The middle end does not warn about expressions that have
 945              been explicitly cast to void, so we must do so here.  */
 946           if (!TREE_SIDE_EFFECTS (expr))
 947             warning (OPT_Wunused_value, "%s has no effect", implicit);
 948           else
 949             {
 950               tree e;
 951               enum tree_code code;
 952               enum tree_code_class class;
 953
 954               e = expr;
 955               /* We might like to warn about (say) "(int) f()", as the
 956                  cast has no effect, but the compiler itself will
 957                  generate implicit conversions under some
 958                  circumstances.  (For example a block copy will be
 959                  turned into a call to "__builtin_memcpy", with a
 960                  conversion of the return value to an appropriate
 961                  type.)  So, to avoid false positives, we strip
 962                  conversions.  Do not use STRIP_NOPs because it will
 963                  not strip conversions to "void", as that is not a
 964                  mode-preserving conversion.  */
 965               while (TREE_CODE (e) == NOP_EXPR)
 966                 e = TREE_OPERAND (e, 0);
 967
 968               code = TREE_CODE (e);
 969               class = TREE_CODE_CLASS (code);
 970               if (class == tcc_comparison
 971                    || class == tcc_unary
 972                    || (class == tcc_binary
 973                        && !(code == MODIFY_EXPR
 974                             || code == INIT_EXPR
 975                             || code == PREDECREMENT_EXPR
 976                             || code == PREINCREMENT_EXPR
 977                             || code == POSTDECREMENT_EXPR
 978                             || code == POSTINCREMENT_EXPR)))
 979                 warning (OPT_Wunused_value, "value computed is not used");
 980             }
 981         }
 982       expr = build1 (CONVERT_EXPR, void_type_node, expr);
 983     }
 984   if (! TREE_SIDE_EFFECTS (expr))
 985     expr = void_zero_node;
 986   return expr;
 987 }
 988
 989 /* Create an expression whose value is that of EXPR,
 990    converted to type TYPE.  The TREE_TYPE of the value
 991    is always TYPE.  This function implements all reasonable
 992    conversions; callers should filter out those that are
 993    not permitted by the language being compiled.
 994
 995    Most of this routine is from build_reinterpret_cast.
 996
 997    The back end cannot call cp_convert (what was convert) because
 998    conversions to/from basetypes may involve memory references
 999    (vbases) and adding or subtracting small values (multiple
1000    inheritance), but it calls convert from the constant folding code
1001    on subtrees of already built trees after it has ripped them apart.
1002
1003    Also, if we ever support range variables, we'll probably also have to
1004    do a little bit more work.  */
1005
1006 tree
1007 convert (tree type, tree expr)
1008 {
1009   tree intype;
1010
1011   if (type == error_mark_node || expr == error_mark_node)
1012     return error_mark_node;
1013
1014   intype = TREE_TYPE (expr);
1015
1016   if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype))
1017     return fold_if_not_in_template (build_nop (type, expr));
1018
1019   return ocp_convert (type, expr, CONV_OLD_CONVERT,
1020                       LOOKUP_NORMAL|LOOKUP_NO_CONVERSION);
1021 }
1022
1023 /* Like cp_convert, except permit conversions to take place which
1024    are not normally allowed due to access restrictions
1025    (such as conversion from sub-type to private super-type).  */
1026
1027 tree
1028 convert_force (tree type, tree expr, int convtype)
1029 {
1030   tree e = expr;
1031   enum tree_code code = TREE_CODE (type);
1032
1033   if (code == REFERENCE_TYPE)
1034     return (fold_if_not_in_template
1035             (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN,
1036                                    NULL_TREE)));
1037
1038   if (code == POINTER_TYPE)
1039     return fold_if_not_in_template (convert_to_pointer_force (type, e));
1040
1041   /* From typeck.c convert_for_assignment */
1042   if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR
1043         && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE
1044         && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE)
1045        || integer_zerop (e)
1046        || TYPE_PTRMEMFUNC_P (TREE_TYPE (e)))
1047       && TYPE_PTRMEMFUNC_P (type))
1048     /* compatible pointer to member functions.  */
1049     return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1,
1050                              /*c_cast_p=*/1);
1051
1052   return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL);
1053 }
1054
1055 /* Convert an aggregate EXPR to type XTYPE.  If a conversion
1056    exists, return the attempted conversion.  This may
1057    return ERROR_MARK_NODE if the conversion is not
1058    allowed (references private members, etc).
1059    If no conversion exists, NULL_TREE is returned.
1060
1061    FIXME: Ambiguity checking is wrong.  Should choose one by the implicit
1062    object parameter, or by the second standard conversion sequence if
1063    that doesn't do it.  This will probably wait for an overloading rewrite.
1064    (jason 8/9/95)  */
1065
1066 static tree
1067 build_type_conversion (tree xtype, tree expr)
1068 {
1069   /* C++: check to see if we can convert this aggregate type
1070      into the required type.  */
1071   return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL);
1072 }
1073
1074 /* Convert the given EXPR to one of a group of types suitable for use in an
1075    expression.  DESIRES is a combination of various WANT_* flags (q.v.)
1076    which indicates which types are suitable.  If COMPLAIN is true, complain
1077    about ambiguity; otherwise, the caller will deal with it.  */
1078
1079 tree
1080 build_expr_type_conversion (int desires, tree expr, bool complain)
1081 {
1082   tree basetype = TREE_TYPE (expr);
1083   tree conv = NULL_TREE;
1084   tree winner = NULL_TREE;
1085
1086   if (expr == null_node
1087       && (desires & WANT_INT)
1088       && !(desires & WANT_NULL))
1089     warning (OPT_Wconversion, "converting NULL to non-pointer type");
1090
1091   basetype = TREE_TYPE (expr);
1092
1093   if (basetype == error_mark_node)
1094     return error_mark_node;
1095
1096   if (! IS_AGGR_TYPE (basetype))
1097     switch (TREE_CODE (basetype))
1098       {
1099       case INTEGER_TYPE:
1100         if ((desires & WANT_NULL) && null_ptr_cst_p (expr))
1101           return expr;
1102         /* else fall through...  */
1103
1104       case BOOLEAN_TYPE:
1105         return (desires & WANT_INT) ? expr : NULL_TREE;
1106       case ENUMERAL_TYPE:
1107         return (desires & WANT_ENUM) ? expr : NULL_TREE;
1108       case REAL_TYPE:
1109         return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1110       case POINTER_TYPE:
1111         return (desires & WANT_POINTER) ? expr : NULL_TREE;
1112
1113       case FUNCTION_TYPE:
1114       case ARRAY_TYPE:
1115         return (desires & WANT_POINTER) ? decay_conversion (expr)
1116                                         : NULL_TREE;
1117
1118       case VECTOR_TYPE:
1119         if ((desires & WANT_VECTOR) == 0)
1120           return NULL_TREE;
1121         switch (TREE_CODE (TREE_TYPE (basetype)))
1122           {
1123           case INTEGER_TYPE:
1124           case BOOLEAN_TYPE:
1125             return (desires & WANT_INT) ? expr : NULL_TREE;
1126           case ENUMERAL_TYPE:
1127             return (desires & WANT_ENUM) ? expr : NULL_TREE;
1128           case REAL_TYPE:
1129             return (desires & WANT_FLOAT) ? expr : NULL_TREE;
1130           default:
1131             return NULL_TREE;
1132           }
1133
1134       default:
1135         return NULL_TREE;
1136       }
1137
1138   /* The code for conversions from class type is currently only used for
1139      delete expressions.  Other expressions are handled by build_new_op.  */
1140   if (!complete_type_or_else (basetype, expr))
1141     return error_mark_node;
1142   if (!TYPE_HAS_CONVERSION (basetype))
1143     return NULL_TREE;
1144
1145   for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv))
1146     {
1147       int win = 0;
1148       tree candidate;
1149       tree cand = TREE_VALUE (conv);
1150
1151       if (winner && winner == cand)
1152         continue;
1153
1154       candidate = non_reference (TREE_TYPE (TREE_TYPE (cand)));
1155
1156       switch (TREE_CODE (candidate))
1157         {
1158         case BOOLEAN_TYPE:
1159         case INTEGER_TYPE:
1160           win = (desires & WANT_INT); break;
1161         case ENUMERAL_TYPE:
1162           win = (desires & WANT_ENUM); break;
1163         case REAL_TYPE:
1164           win = (desires & WANT_FLOAT); break;
1165         case POINTER_TYPE:
1166           win = (desires & WANT_POINTER); break;
1167
1168         case VECTOR_TYPE:
1169           if ((desires & WANT_VECTOR) == 0)
1170             break;
1171           switch (TREE_CODE (TREE_TYPE (candidate)))
1172             {
1173             case BOOLEAN_TYPE:
1174             case INTEGER_TYPE:
1175               win = (desires & WANT_INT); break;
1176             case ENUMERAL_TYPE:
1177               win = (desires & WANT_ENUM); break;
1178             case REAL_TYPE:
1179               win = (desires & WANT_FLOAT); break;
1180             default:
1181               break;
1182             }
1183           break;
1184
1185         default:
1186           break;
1187         }
1188
1189       if (win)
1190         {
1191           if (winner)
1192             {
1193               if (complain)
1194                 {
1195                   error ("ambiguous default type conversion from %qT",
1196                          basetype);
1197                   error ("  candidate conversions include %qD and %qD",
1198                          winner, cand);
1199                 }
1200               return error_mark_node;
1201             }
1202           else
1203             winner = cand;
1204         }
1205     }
1206
1207   if (winner)
1208     {
1209       tree type = non_reference (TREE_TYPE (TREE_TYPE (winner)));
1210       return build_user_type_conversion (type, expr, LOOKUP_NORMAL);
1211     }
1212
1213   return NULL_TREE;
1214 }
1215
1216 /* Implements integral promotion (4.1) and float->double promotion.  */
1217
1218 tree
1219 type_promotes_to (tree type)
1220 {
1221   if (type == error_mark_node)
1222     return error_mark_node;
1223
1224   type = TYPE_MAIN_VARIANT (type);
1225
1226   /* bool always promotes to int (not unsigned), even if it's the same
1227      size.  */
1228   if (type == boolean_type_node)
1229     type = integer_type_node;
1230
1231   /* Normally convert enums to int, but convert wide enums to something
1232      wider.  */
1233   else if (TREE_CODE (type) == ENUMERAL_TYPE
1234            || type == wchar_type_node)
1235     {
1236       int precision = MAX (TYPE_PRECISION (type),
1237                            TYPE_PRECISION (integer_type_node));
1238       tree totype = c_common_type_for_size (precision, 0);
1239       if (TYPE_UNSIGNED (type)
1240           && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype))
1241         type = c_common_type_for_size (precision, 1);
1242       else
1243         type = totype;
1244     }
1245   else if (c_promoting_integer_type_p (type))
1246     {
1247       /* Retain unsignedness if really not getting bigger.  */
1248       if (TYPE_UNSIGNED (type)
1249           && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node))
1250         type = unsigned_type_node;
1251       else
1252         type = integer_type_node;
1253     }
1254   else if (type == float_type_node)
1255     type = double_type_node;
1256
1257   return type;
1258 }
1259
1260 /* The routines below this point are carefully written to conform to
1261    the standard.  They use the same terminology, and follow the rules
1262    closely.  Although they are used only in pt.c at the moment, they
1263    should presumably be used everywhere in the future.  */
1264
1265 /* Attempt to perform qualification conversions on EXPR to convert it
1266    to TYPE.  Return the resulting expression, or error_mark_node if
1267    the conversion was impossible.  */
1268
1269 tree
1270 perform_qualification_conversions (tree type, tree expr)
1271 {
1272   tree expr_type;
1273
1274   expr_type = TREE_TYPE (expr);
1275
1276   if (same_type_p (type, expr_type))
1277     return expr;
1278   else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type)
1279            && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type)))
1280     return build_nop (type, expr);
1281   else if (TYPE_PTR_TO_MEMBER_P (type)
1282            && TYPE_PTR_TO_MEMBER_P (expr_type)
1283            && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type),
1284                            TYPE_PTRMEM_CLASS_TYPE (expr_type))
1285            && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type),
1286                                TYPE_PTRMEM_POINTED_TO_TYPE (expr_type)))
1287     return build_nop (type, expr);
1288   else
1289     return error_mark_node;
1290 }