expression.c

   1 /*
   2  * sparse/expression.c
   3  *
   4  * Copyright (C) 2003 Transmeta Corp.
   5  *               2003-2004 Linus Torvalds
   6  *
   7  *  Licensed under the Open Software License version 1.1
   8  *
   9  * This is the expression parsing part of parsing C.
  10  */
  11 #include <stdarg.h>
  12 #include <stdlib.h>
  13 #include <stdio.h>
  14 #include <string.h>
  15 #include <ctype.h>
  16 #include <unistd.h>
  17 #include <fcntl.h>
  18 #include <errno.h>
  19 #include <limits.h>
  20
  21 #include "lib.h"
  22 #include "allocate.h"
  23 #include "allocate.h"
  24 #include "token.h"
  25 #include "parse.h"
  26 #include "symbol.h"
  27 #include "scope.h"
  28 #include "expression.h"
  29 #include "target.h"
  30
  31 static int match_oplist(int op, ...)
  32 {
  33         va_list args;
  34
  35         va_start(args, op);
  36         for (;;) {
  37                 int nextop = va_arg(args, int);
  38                 if (!nextop)
  39                         return 0;
  40                 if (op == nextop)
  41                         return 1;
  42         }
  43 }
  44
  45 static struct token *comma_expression(struct token *, struct expression **);
  46
  47 struct token *parens_expression(struct token *token, struct expression **expr, const char *where)
  48 {
  49         token = expect(token, '(', where);
  50         if (match_op(token, '{')) {
  51                 struct expression *e = alloc_expression(token->pos, EXPR_STATEMENT);
  52                 struct statement *stmt = alloc_statement(token->pos, STMT_COMPOUND);
  53                 *expr = e;
  54                 e->statement = stmt;
  55                 start_symbol_scope();
  56                 token = compound_statement(token->next, stmt);
  57                 end_symbol_scope();
  58                 token = expect(token, '}', "at end of statement expression");
  59         } else
  60                 token = parse_expression(token, expr);
  61         return expect(token, ')', where);
  62 }
  63
  64 /*
  65  * Handle __func__, __FUNCTION__ and __PRETTY_FUNCTION__ token
  66  * conversion
  67  */
  68 static int convert_one_fn_token(struct token *token)
  69 {
  70         struct symbol *sym = current_fn;
  71
  72         if (sym) {
  73                 struct ident *ident = sym->ident;
  74                 if (ident) {
  75                         int len = ident->len;
  76                         struct string *string;
  77
  78                         string = __alloc_string(len+1);
  79                         memcpy(string->data, ident->name, len);
  80                         string->data[len] = 0;
  81                         string->length = len+1;
  82                         token_type(token) = TOKEN_STRING;
  83                         token->string = string;
  84                         return 1;
  85                 }
  86         }
  87         return 0;
  88 }
  89
  90 static int convert_function(struct token *next)
  91 {
  92         int retval = 0;
  93         for (;;) {
  94                 struct token *token = next;
  95                 next = next->next;
  96                 switch (token_type(token)) {
  97                 case TOKEN_STRING:
  98                         continue;
  99                 case TOKEN_IDENT:
 100                         if (token->ident == &__func___ident ||
 101                             token->ident == &__FUNCTION___ident ||
 102                             token->ident == &__PRETTY_FUNCTION___ident) {
 103                                 if (!convert_one_fn_token(token))
 104                                         break;
 105                                 retval = 1;
 106                                 continue;
 107                         }
 108                 /* Fall through */
 109                 default:
 110                         break;
 111                 }
 112                 break;
 113         }
 114         return retval;
 115 }
 116
 117 static struct token *string_expression(struct token *token, struct expression *expr)
 118 {
 119         struct string *string = token->string;
 120         struct token *next = token->next;
 121
 122         convert_function(token);
 123
 124         if (token_type(next) == TOKEN_STRING) {
 125                 int totlen = string->length-1;
 126                 char *data;
 127
 128                 do {
 129                         totlen += next->string->length-1;
 130                         next = next->next;
 131                 } while (token_type(next) == TOKEN_STRING);
 132
 133                 if (totlen > MAX_STRING) {
 134                         warning(token->pos, "trying to concatenate %d-character string (%d bytes max)", totlen, MAX_STRING);
 135                         totlen = MAX_STRING;
 136                 }
 137
 138                 string = __alloc_string(totlen+1);
 139                 string->length = totlen+1;
 140                 data = string->data;
 141                 next = token;
 142                 do {
 143                         struct string *s = next->string;
 144                         int len = s->length-1;
 145
 146                         if (len > totlen)
 147                                 len = totlen;
 148                         totlen -= len;
 149
 150                         next = next->next;
 151                         memcpy(data, s->data, len);
 152                         data += len;
 153                 } while (token_type(next) == TOKEN_STRING);
 154                 *data = '\0';
 155         }
 156         expr->string = string;
 157         return next;
 158 }
 159
 160 #ifndef ULLONG_MAX
 161 #define ULLONG_MAX (~0ULL)
 162 #endif
 163
 164 static void get_number_value(struct expression *expr, struct token *token)
 165 {
 166         const char *str = token->number;
 167         unsigned long long value;
 168         char *end;
 169         unsigned long modifiers = 0;
 170         int overflow = 0, do_warn = 0;
 171         int try_unsigned = 1;
 172         int bits;
 173
 174         errno = 0;
 175         value = strtoull(str, &end, 0);
 176         if (end == str)
 177                 goto Float;
 178         if (value == ULLONG_MAX && errno == ERANGE)
 179                 overflow = 1;
 180         while (1) {
 181                 unsigned long added;
 182                 char c = *end++;
 183                 if (!c) {
 184                         break;
 185                 } else if (c == 'u' || c == 'U') {
 186                         added = MOD_UNSIGNED;
 187                 } else if (c == 'l' || c == 'L') {
 188                         added = MOD_LONG;
 189                         if (*end == c) {
 190                                 added |= MOD_LONGLONG;
 191                                 end++;
 192                         }
 193                 } else
 194                         goto Float;
 195                 if (modifiers & added)
 196                         goto Enoint;
 197                 modifiers |= added;
 198         }
 199         if (overflow)
 200                 goto Eoverflow;
 201         /* OK, it's a valid integer */
 202         /* decimals can be unsigned only if directly specified as such */
 203         if (str[0] != '0' && !(modifiers & MOD_UNSIGNED))
 204                 try_unsigned = 0;
 205         if (!(modifiers & MOD_LONG)) {
 206                 bits = bits_in_int - 1;
 207                 if (!(value & (~1ULL << bits))) {
 208                         if (!(value & (1ULL << bits))) {
 209                                 goto got_it;
 210                         } else if (try_unsigned) {
 211                                 modifiers |= MOD_UNSIGNED;
 212                                 goto got_it;
 213                         }
 214                 }
 215                 modifiers |= MOD_LONG;
 216                 do_warn = 1;
 217         }
 218         if (!(modifiers & MOD_LONGLONG)) {
 219                 bits = bits_in_long - 1;
 220                 if (!(value & (~1ULL << bits))) {
 221                         if (!(value & (1ULL << bits))) {
 222                                 goto got_it;
 223                         } else if (try_unsigned) {
 224                                 modifiers |= MOD_UNSIGNED;
 225                                 goto got_it;
 226                         }
 227                         do_warn |= 2;
 228                 }
 229                 modifiers |= MOD_LONGLONG;
 230                 do_warn |= 1;
 231         }
 232         bits = bits_in_longlong - 1;
 233         if (value & (~1ULL << bits))
 234                 goto Eoverflow;
 235         if (!(value & (1ULL << bits)))
 236                 goto got_it;
 237         if (!try_unsigned)
 238                 warning(expr->pos, "decimal constant %s is too big for long long",
 239                         show_token(token));
 240         modifiers |= MOD_UNSIGNED;
 241 got_it:
 242         if (do_warn)
 243                 warning(expr->pos, "constant %s is so big it is%s%s%s",
 244                         show_token(token),
 245                         (modifiers & MOD_UNSIGNED) ? " unsigned":"",
 246                         (modifiers & MOD_LONG) ? " long":"",
 247                         (modifiers & MOD_LONGLONG) ? " long":"");
 248         if (do_warn & 2)
 249                 warning(expr->pos,
 250                         "decimal constant %s is between LONG_MAX and ULONG_MAX."
 251                         " For C99 that means long long, C90 compilers are very "
 252                         "likely to produce unsigned long (and a warning) here",
 253                         show_token(token));
 254         expr->type = EXPR_VALUE;
 255         expr->ctype = ctype_integer(modifiers);
 256         expr->value = value;
 257         return;
 258 Eoverflow:
 259         error_die(expr->pos, "constant %s is too big even for unsigned long long",
 260                         show_token(token));
 261         return;
 262 Float:
 263         expr->fvalue = string_to_ld(str, &end);
 264         if (str == end)
 265                 goto Enoint;
 266
 267         if (*end && end[1])
 268                 goto Enoint;
 269
 270         if (*end == 'f' || *end == 'F')
 271                 expr->ctype = &float_ctype;
 272         else if (*end == 'l' || *end == 'L')
 273                 expr->ctype = &ldouble_ctype;
 274         else if (!*end)
 275                 expr->ctype = &double_ctype;
 276         else
 277                 goto Enoint;
 278
 279         expr->type = EXPR_FVALUE;
 280         return;
 281
 282 Enoint:
 283         error_die(expr->pos, "constant %s is not a valid number", show_token(token));
 284 }
 285
 286 struct token *primary_expression(struct token *token, struct expression **tree)
 287 {
 288         struct expression *expr = NULL;
 289
 290         switch (token_type(token)) {
 291         case TOKEN_CHAR:
 292                 expr = alloc_expression(token->pos, EXPR_VALUE);
 293                 expr->ctype = &int_ctype;
 294                 expr->value = (unsigned char) token->character;
 295                 token = token->next;
 296                 break;
 297
 298         case TOKEN_NUMBER:
 299                 expr = alloc_expression(token->pos, EXPR_VALUE);
 300                 get_number_value(expr, token);
 301                 token = token->next;
 302                 break;
 303
 304         case TOKEN_IDENT: {
 305                 struct symbol *sym = lookup_symbol(token->ident, NS_SYMBOL | NS_TYPEDEF);
 306                 struct token *next = token->next;
 307
 308                 if (!sym && convert_function(token))
 309                         goto handle_string;
 310
 311                 expr = alloc_expression(token->pos, EXPR_SYMBOL);
 312
 313                 /*
 314                  * We support types as real first-class citizens, with type
 315                  * comparisons etc:
 316                  *
 317                  *      if (typeof(a) == int) ..
 318                  */
 319                 if (sym && sym->namespace == NS_TYPEDEF) {
 320                         warning(token->pos, "typename in expression");
 321                         sym = NULL;
 322                 }
 323                 expr->symbol_name = token->ident;
 324                 expr->symbol = sym;
 325                 token = next;
 326                 break;
 327         }
 328
 329         case TOKEN_STRING: {
 330         handle_string:
 331                 expr = alloc_expression(token->pos, EXPR_STRING);
 332                 token = string_expression(token, expr);
 333                 break;
 334         }
 335
 336         case TOKEN_SPECIAL:
 337                 if (token->special == '(') {
 338                         expr = alloc_expression(token->pos, EXPR_PREOP);
 339                         expr->op = '(';
 340                         token = parens_expression(token, &expr->unop, "in expression");
 341                         break;
 342                 }
 343                 if (token->special == '[' && lookup_type(token->next)) {
 344                         expr = alloc_expression(token->pos, EXPR_TYPE);
 345                         token = typename(token->next, &expr->symbol);
 346                         token = expect(token, ']', "in type expression");
 347                         break;
 348                 }
 349
 350         default:
 351                 ;
 352         }
 353         *tree = expr;
 354         return token;
 355 }
 356
 357 static struct token *expression_list(struct token *token, struct expression_list **list)
 358 {
 359         while (!match_op(token, ')')) {
 360                 struct expression *expr = NULL;
 361                 token = assignment_expression(token, &expr);
 362                 if (!expr)
 363                         break;
 364                 add_expression(list, expr);
 365                 if (!match_op(token, ','))
 366                         break;
 367                 token = token->next;
 368         }
 369         return token;
 370 }
 371
 372 /*
 373  * extend to deal with the ambiguous C grammar for parsing
 374  * a cast expressions followed by an initializer.
 375  */
 376 static struct token *postfix_expression(struct token *token, struct expression **tree, struct expression *cast_init_expr)
 377 {
 378         struct expression *expr = cast_init_expr;
 379
 380         if (!expr)
 381                 token = primary_expression(token, &expr);
 382
 383         while (expr && token_type(token) == TOKEN_SPECIAL) {
 384                 switch (token->special) {
 385                 case '[': {                     /* Array dereference */
 386                         struct expression *deref = alloc_expression(token->pos, EXPR_PREOP);
 387                         struct expression *add = alloc_expression(token->pos, EXPR_BINOP);
 388
 389                         deref->op = '*';
 390                         deref->unop = add;
 391
 392                         add->op = '+';
 393                         add->left = expr;
 394                         token = parse_expression(token->next, &add->right);
 395                         token = expect(token, ']', "at end of array dereference");
 396                         expr = deref;
 397                         continue;
 398                 }
 399                 case SPECIAL_INCREMENT:         /* Post-increment */
 400                 case SPECIAL_DECREMENT: {       /* Post-decrement */
 401                         struct expression *post = alloc_expression(token->pos, EXPR_POSTOP);
 402                         post->op = token->special;
 403                         post->unop = expr;
 404                         expr = post;
 405                         token = token->next;
 406                         continue;
 407                 }
 408                 case SPECIAL_DEREFERENCE: {     /* Structure pointer member dereference */
 409                         /* "x->y" is just shorthand for "(*x).y" */
 410                         struct expression *inner = alloc_expression(token->pos, EXPR_PREOP);
 411                         inner->op = '*';
 412                         inner->unop = expr;
 413                         expr = inner;
 414                 }
 415                 /* Fallthrough!! */
 416                 case '.': {                     /* Structure member dereference */
 417                         struct expression *deref = alloc_expression(token->pos, EXPR_DEREF);
 418                         deref->op = '.';
 419                         deref->deref = expr;
 420                         token = token->next;
 421                         if (token_type(token) != TOKEN_IDENT) {
 422                                 warning(token->pos, "Expected member name");
 423                                 break;
 424                         }
 425                         deref->member = token->ident;
 426                         token = token->next;
 427                         expr = deref;
 428                         continue;
 429                 }
 430
 431                 case '(': {                     /* Function call */
 432                         struct expression *call = alloc_expression(token->pos, EXPR_CALL);
 433                         call->op = '(';
 434                         call->fn = expr;
 435                         token = expression_list(token->next, &call->args);
 436                         token = expect(token, ')', "in function call");
 437                         expr = call;
 438                         continue;
 439                 }
 440
 441                 default:
 442                         break;
 443                 }
 444                 break;
 445         }
 446         *tree = expr;
 447         return token;
 448 }
 449
 450 static struct token *cast_expression(struct token *token, struct expression **tree);
 451 static struct token *unary_expression(struct token *token, struct expression **tree);
 452
 453 static struct token *type_info_expression(struct token *token,
 454         struct expression **tree, int type)
 455 {
 456         struct expression *expr = alloc_expression(token->pos, type);
 457
 458         *tree = expr;
 459         token = token->next;
 460         if (!match_op(token, '(') || !lookup_type(token->next))
 461                 return unary_expression(token, &expr->cast_expression);
 462         token = typename(token->next, &expr->cast_type);
 463
 464         if (!match_op(token, ')')) {
 465                 static const char * error[] = {
 466                         [EXPR_SIZEOF] = "at end of sizeof",
 467                         [EXPR_ALIGNOF] = "at end of __alignof__",
 468                         [EXPR_PTRSIZEOF] = "at end of __sizeof_ptr__"
 469                 };
 470                 return expect(token, ')', error[type]);
 471         }
 472
 473         token = token->next;
 474         /*
 475          * C99 ambiguity: the typename might have been the beginning
 476          * of a typed initializer expression..
 477          */
 478         if (match_op(token, '{'))
 479                 token = initializer(&expr->cast_expression, token);
 480         return token;
 481 }
 482
 483 static struct token *unary_expression(struct token *token, struct expression **tree)
 484 {
 485         if (token_type(token) == TOKEN_IDENT) {
 486                 struct ident *ident = token->ident;
 487                 if (ident->reserved) {
 488                         static const struct {
 489                                 struct ident *id;
 490                                 int type;
 491                         } type_information[] = {
 492                                 { &sizeof_ident, EXPR_SIZEOF },
 493                                 { &__alignof___ident, EXPR_ALIGNOF },
 494                                 { &__sizeof_ptr___ident, EXPR_PTRSIZEOF },
 495                         };
 496                         int i;
 497                         for (i = 0; i < 3; i++) {
 498                                 if (ident == type_information[i].id)
 499                                         return type_info_expression(token, tree, type_information[i].type);
 500                         }
 501                 }
 502         }
 503
 504         if (token_type(token) == TOKEN_SPECIAL) {
 505                 if (match_oplist(token->special,
 506                     SPECIAL_INCREMENT, SPECIAL_DECREMENT,
 507                     '&', '*', '+', '-', '~', '!', 0)) {
 508                         struct expression *unop;
 509                         struct expression *unary;
 510                         struct token *next;
 511
 512                         next = cast_expression(token->next, &unop);
 513                         if (!unop) {
 514                                 warning(token->pos, "Syntax error in unary expression");
 515                                 return next;
 516                         }
 517                         unary = alloc_expression(token->pos, EXPR_PREOP);
 518                         unary->op = token->special;
 519                         unary->unop = unop;
 520                         *tree = unary;
 521                         return next;
 522                 }
 523
 524                 /* Gcc extension: &&label gives the address of a label */
 525                 if (match_op(token, SPECIAL_LOGICAL_AND) &&
 526                     token_type(token->next) == TOKEN_IDENT) {
 527                         struct expression *label = alloc_expression(token->pos, EXPR_LABEL);
 528                         struct symbol *sym = label_symbol(token->next);
 529                         if (!(sym->ctype.modifiers & MOD_ADDRESSABLE)) {
 530                                 sym->ctype.modifiers |= MOD_ADDRESSABLE;
 531                                 add_symbol(&function_computed_target_list, sym);
 532                         }
 533                         label->label_symbol = sym;
 534                         *tree = label;
 535                         return token->next->next;
 536                 }
 537
 538         }
 539
 540         return postfix_expression(token, tree, NULL);
 541 }
 542
 543 /*
 544  * Ambiguity: a '(' can be either a cast-expression or
 545  * a primary-expression depending on whether it is followed
 546  * by a type or not.
 547  *
 548  * additional ambiguity: a "cast expression" followed by
 549  * an initializer is really a postfix-expression.
 550  */
 551 static struct token *cast_expression(struct token *token, struct expression **tree)
 552 {
 553         if (match_op(token, '(')) {
 554                 struct token *next = token->next;
 555                 if (lookup_type(next)) {
 556                         struct expression *cast = alloc_expression(next->pos, EXPR_CAST);
 557                         struct symbol *sym;
 558
 559                         token = typename(next, &sym);
 560                         cast->cast_type = sym;
 561                         token = expect(token, ')', "at end of cast operator");
 562                         if (match_op(token, '{')) {
 563                                 token = initializer(&cast->cast_expression, token);
 564                                 return postfix_expression(token, tree, cast);
 565                         }
 566                         *tree = cast;
 567                         token = cast_expression(token, &cast->cast_expression);
 568                         return token;
 569                 }
 570         }
 571         return unary_expression(token, tree);
 572 }
 573
 574 /*
 575  * Generic left-to-right binop parsing
 576  *
 577  * This _really_ needs to be inlined, because that makes the inner
 578  * function call statically deterministic rather than a totally
 579  * unpredictable indirect call. But gcc-3 is so "clever" that it
 580  * doesn't do so by default even when you tell it to inline it.
 581  *
 582  * Making it a macro avoids the inlining problem, and also means
 583  * that we can pass in the op-comparison as an expression rather
 584  * than create a data structure for it.
 585  */
 586
 587 #define LR_BINOP_EXPRESSION(token, tree, type, inner, compare)          \
 588         struct expression *left = NULL;                                 \
 589         struct token * next = inner(token, &left);                      \
 590                                                                         \
 591         if (left) {                                                     \
 592                 while (token_type(next) == TOKEN_SPECIAL) {             \
 593                         struct expression *top, *right = NULL;          \
 594                         int op = next->special;                         \
 595                                                                         \
 596                         if (!(compare))                                 \
 597                                 goto out;                               \
 598                         top = alloc_expression(next->pos, type);        \
 599                         next = inner(next->next, &right);               \
 600                         if (!right) {                                   \
 601                                 warning(next->pos, "No right hand side of '%s'-expression", show_special(op));  \
 602                                 break;                                  \
 603                         }                                               \
 604                         top->op = op;                                   \
 605                         top->left = left;                               \
 606                         top->right = right;                             \
 607                         left = top;                                     \
 608                 }                                                       \
 609         }                                                               \
 610 out:                                                                    \
 611         *tree = left;                                                   \
 612         return next;                                                    \
 613
 614
 615 static struct token *multiplicative_expression(struct token *token, struct expression **tree)
 616 {
 617         LR_BINOP_EXPRESSION(
 618                 token, tree, EXPR_BINOP, cast_expression,
 619                 (op == '*') || (op == '/') || (op == '%')
 620         );
 621 }
 622
 623 static struct token *additive_expression(struct token *token, struct expression **tree)
 624 {
 625         LR_BINOP_EXPRESSION(
 626                 token, tree, EXPR_BINOP, multiplicative_expression,
 627                 (op == '+') || (op == '-')
 628         );
 629 }
 630
 631 static struct token *shift_expression(struct token *token, struct expression **tree)
 632 {
 633         LR_BINOP_EXPRESSION(
 634                 token, tree, EXPR_BINOP, additive_expression,
 635                 (op == SPECIAL_LEFTSHIFT) || (op == SPECIAL_RIGHTSHIFT)
 636         );
 637 }
 638
 639 static struct token *relational_expression(struct token *token, struct expression **tree)
 640 {
 641         LR_BINOP_EXPRESSION(
 642                 token, tree, EXPR_COMPARE, shift_expression,
 643                 (op == '<') || (op == '>') ||
 644                 (op == SPECIAL_LTE) || (op == SPECIAL_GTE)
 645         );
 646 }
 647
 648 static struct token *equality_expression(struct token *token, struct expression **tree)
 649 {
 650         LR_BINOP_EXPRESSION(
 651                 token, tree, EXPR_COMPARE, relational_expression,
 652                 (op == SPECIAL_EQUAL) || (op == SPECIAL_NOTEQUAL)
 653         );
 654 }
 655
 656 static struct token *bitwise_and_expression(struct token *token, struct expression **tree)
 657 {
 658         LR_BINOP_EXPRESSION(
 659                 token, tree, EXPR_BINOP, equality_expression,
 660                 (op == '&')
 661         );
 662 }
 663
 664 static struct token *bitwise_xor_expression(struct token *token, struct expression **tree)
 665 {
 666         LR_BINOP_EXPRESSION(
 667                 token, tree, EXPR_BINOP, bitwise_and_expression,
 668                 (op == '^')
 669         );
 670 }
 671
 672 static struct token *bitwise_or_expression(struct token *token, struct expression **tree)
 673 {
 674         LR_BINOP_EXPRESSION(
 675                 token, tree, EXPR_BINOP, bitwise_xor_expression,
 676                 (op == '|')
 677         );
 678 }
 679
 680 static struct token *logical_and_expression(struct token *token, struct expression **tree)
 681 {
 682         LR_BINOP_EXPRESSION(
 683                 token, tree, EXPR_LOGICAL, bitwise_or_expression,
 684                 (op == SPECIAL_LOGICAL_AND)
 685         );
 686 }
 687
 688 static struct token *logical_or_expression(struct token *token, struct expression **tree)
 689 {
 690         LR_BINOP_EXPRESSION(
 691                 token, tree, EXPR_LOGICAL, logical_and_expression,
 692                 (op == SPECIAL_LOGICAL_OR)
 693         );
 694 }
 695
 696 struct token *conditional_expression(struct token *token, struct expression **tree)
 697 {
 698         token = logical_or_expression(token, tree);
 699         if (*tree && match_op(token, '?')) {
 700                 struct expression *expr = alloc_expression(token->pos, EXPR_CONDITIONAL);
 701                 expr->op = token->special;
 702                 expr->left = *tree;
 703                 *tree = expr;
 704                 token = parse_expression(token->next, &expr->cond_true);
 705                 token = expect(token, ':', "in conditional expression");
 706                 token = conditional_expression(token, &expr->cond_false);
 707         }
 708         return token;
 709 }
 710
 711 struct token *assignment_expression(struct token *token, struct expression **tree)
 712 {
 713         token = conditional_expression(token, tree);
 714         if (*tree && token_type(token) == TOKEN_SPECIAL) {
 715                 static const int assignments[] = {
 716                         '=',
 717                         SPECIAL_ADD_ASSIGN, SPECIAL_SUB_ASSIGN,
 718                         SPECIAL_MUL_ASSIGN, SPECIAL_DIV_ASSIGN,
 719                         SPECIAL_MOD_ASSIGN, SPECIAL_SHL_ASSIGN,
 720                         SPECIAL_SHR_ASSIGN, SPECIAL_AND_ASSIGN,
 721                         SPECIAL_OR_ASSIGN,  SPECIAL_XOR_ASSIGN };
 722                 int i, op = token->special;
 723                 for (i = 0; i < sizeof(assignments)/sizeof(int); i++)
 724                         if (assignments[i] == op) {
 725                                 struct expression * expr = alloc_expression(token->pos, EXPR_ASSIGNMENT);
 726                                 expr->left = *tree;
 727                                 expr->op = op;
 728                                 *tree = expr;
 729                                 return assignment_expression(token->next, &expr->right);
 730                         }
 731         }
 732         return token;
 733 }
 734
 735 static struct token *comma_expression(struct token *token, struct expression **tree)
 736 {
 737         LR_BINOP_EXPRESSION(
 738                 token, tree, EXPR_COMMA, assignment_expression,
 739                 (op == ',')
 740         );
 741 }
 742
 743 struct token *parse_expression(struct token *token, struct expression **tree)
 744 {
 745         return comma_expression(token,tree);
 746 }
 747
 748