libiberty/d-demangle.c

   1 /* Demangler for the D programming language
   2    Copyright (C) 2014-2023 Free Software Foundation, Inc.
   3    Written by Iain Buclaw (ibuclaw@gdcproject.org)
   4
   5 This file is part of the libiberty library.
   6 Libiberty is free software; you can redistribute it and/or
   7 modify it under the terms of the GNU Library General Public
   8 License as published by the Free Software Foundation; either
   9 version 2 of the License, or (at your option) any later version.
  10
  11 In addition to the permissions in the GNU Library General Public
  12 License, the Free Software Foundation gives you unlimited permission
  13 to link the compiled version of this file into combinations with other
  14 programs, and to distribute those combinations without any restriction
  15 coming from the use of this file.  (The Library Public License
  16 restrictions do apply in other respects; for example, they cover
  17 modification of the file, and distribution when not linked into a
  18 combined executable.)
  19
  20 Libiberty is distributed in the hope that it will be useful,
  21 but WITHOUT ANY WARRANTY; without even the implied warranty of
  22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  23 Library General Public License for more details.
  24
  25 You should have received a copy of the GNU Library General Public
  26 License along with libiberty; see the file COPYING.LIB.
  27 If not, see <http://www.gnu.org/licenses/>.  */
  28
  29 /* This file exports one function; dlang_demangle.  */
  30
  31 #ifdef HAVE_CONFIG_H
  32 #include "config.h"
  33 #endif
  34 #ifdef HAVE_LIMITS_H
  35 #include <limits.h>
  36 #endif
  37
  38 #include "safe-ctype.h"
  39
  40 #include <sys/types.h>
  41 #include <string.h>
  42 #include <stdio.h>
  43
  44 #ifdef HAVE_STDLIB_H
  45 #include <stdlib.h>
  46 #endif
  47
  48 #include <demangle.h>
  49 #include "libiberty.h"
  50
  51 #ifndef ULONG_MAX
  52 #define ULONG_MAX       (~0UL)
  53 #endif
  54 #ifndef UINT_MAX
  55 #define UINT_MAX        (~0U)
  56 #endif
  57
  58 /* A mini string-handling package */
  59
  60 typedef struct string           /* Beware: these aren't required to be */
  61 {                               /*  '\0' terminated.  */
  62   char *b;                      /* pointer to start of string */
  63   char *p;                      /* pointer after last character */
  64   char *e;                      /* pointer after end of allocated space */
  65 } string;
  66
  67 static void
  68 string_need (string *s, size_t n)
  69 {
  70   size_t tem;
  71
  72   if (s->b == NULL)
  73     {
  74       if (n < 32)
  75         {
  76           n = 32;
  77         }
  78       s->p = s->b = XNEWVEC (char, n);
  79       s->e = s->b + n;
  80     }
  81   else if ((size_t) (s->e - s->p) < n)
  82     {
  83       tem = s->p - s->b;
  84       n += tem;
  85       n *= 2;
  86       s->b = XRESIZEVEC (char, s->b, n);
  87       s->p = s->b + tem;
  88       s->e = s->b + n;
  89     }
  90 }
  91
  92 static void
  93 string_delete (string *s)
  94 {
  95   if (s->b != NULL)
  96     {
  97       XDELETEVEC (s->b);
  98       s->b = s->e = s->p = NULL;
  99     }
 100 }
 101
 102 static void
 103 string_init (string *s)
 104 {
 105   s->b = s->p = s->e = NULL;
 106 }
 107
 108 static int
 109 string_length (string *s)
 110 {
 111   if (s->p == s->b)
 112     {
 113       return 0;
 114     }
 115   return s->p - s->b;
 116 }
 117
 118 static void
 119 string_setlength (string *s, int n)
 120 {
 121   if (n - string_length (s) < 0)
 122     {
 123       s->p = s->b + n;
 124     }
 125 }
 126
 127 static void
 128 string_append (string *p, const char *s)
 129 {
 130   size_t n = strlen (s);
 131   string_need (p, n);
 132   memcpy (p->p, s, n);
 133   p->p += n;
 134 }
 135
 136 static void
 137 string_appendn (string *p, const char *s, size_t n)
 138 {
 139   if (n != 0)
 140     {
 141       string_need (p, n);
 142       memcpy (p->p, s, n);
 143       p->p += n;
 144     }
 145 }
 146
 147 static void
 148 string_prependn (string *p, const char *s, size_t n)
 149 {
 150   char *q;
 151
 152   if (n != 0)
 153     {
 154       string_need (p, n);
 155       for (q = p->p - 1; q >= p->b; q--)
 156         {
 157           q[n] = q[0];
 158         }
 159       memcpy (p->b, s, n);
 160       p->p += n;
 161     }
 162 }
 163
 164 static void
 165 string_prepend (string *p, const char *s)
 166 {
 167   if (s != NULL && *s != '\0')
 168     {
 169       string_prependn (p, s, strlen (s));
 170     }
 171 }
 172
 173 /* Demangle information structure we pass around.  */
 174 struct dlang_info
 175 {
 176   /* The string we are demangling.  */
 177   const char *s;
 178   /* The index of the last back reference.  */
 179   int last_backref;
 180 };
 181
 182 /* Pass as the LEN to dlang_parse_template if symbol length is not known.  */
 183 #define TEMPLATE_LENGTH_UNKNOWN (-1UL)
 184
 185 /* Prototypes for forward referenced functions */
 186 static const char *dlang_function_type (string *, const char *,
 187                                         struct dlang_info *);
 188
 189 static const char *dlang_function_args (string *, const char *,
 190                                         struct dlang_info *);
 191
 192 static const char *dlang_type (string *, const char *, struct dlang_info *);
 193
 194 static const char *dlang_value (string *, const char *, const char *, char,
 195                                 struct dlang_info *);
 196
 197 static const char *dlang_parse_qualified (string *, const char *,
 198                                           struct dlang_info *, int);
 199
 200 static const char *dlang_parse_mangle (string *, const char *,
 201                                        struct dlang_info *);
 202
 203 static const char *dlang_parse_tuple (string *, const char *,
 204                                       struct dlang_info *);
 205
 206 static const char *dlang_parse_template (string *, const char *,
 207                                          struct dlang_info *, unsigned long);
 208
 209 static const char *dlang_lname (string *, const char *, unsigned long);
 210
 211
 212 /* Extract the number from MANGLED, and assign the result to RET.
 213    Return the remaining string on success or NULL on failure.
 214    A result larger than UINT_MAX is considered a failure.  */
 215 static const char *
 216 dlang_number (const char *mangled, unsigned long *ret)
 217 {
 218   /* Return NULL if trying to extract something that isn't a digit.  */
 219   if (mangled == NULL || !ISDIGIT (*mangled))
 220     return NULL;
 221
 222   unsigned long val = 0;
 223
 224   while (ISDIGIT (*mangled))
 225     {
 226       unsigned long digit = mangled[0] - '0';
 227
 228       /* Check for overflow.  */
 229       if (val > (UINT_MAX - digit) / 10)
 230         return NULL;
 231
 232       val = val * 10 + digit;
 233       mangled++;
 234     }
 235
 236   if (*mangled == '\0')
 237     return NULL;
 238
 239   *ret = val;
 240   return mangled;
 241 }
 242
 243 /* Extract the hex-digit from MANGLED, and assign the result to RET.
 244    Return the remaining string on success or NULL on failure.  */
 245 static const char *
 246 dlang_hexdigit (const char *mangled, char *ret)
 247 {
 248   char c;
 249
 250   /* Return NULL if trying to extract something that isn't a hexdigit.  */
 251   if (mangled == NULL || !ISXDIGIT (mangled[0]) || !ISXDIGIT (mangled[1]))
 252     return NULL;
 253
 254   c = mangled[0];
 255   if (!ISDIGIT (c))
 256     *ret = c - (ISUPPER (c) ? 'A' : 'a') + 10;
 257   else
 258     *ret = c - '0';
 259
 260   c = mangled[1];
 261   if (!ISDIGIT (c))
 262     *ret = (*ret << 4) | (c - (ISUPPER (c) ? 'A' : 'a') + 10);
 263   else
 264     *ret = (*ret << 4) | (c - '0');
 265
 266   mangled += 2;
 267
 268   return mangled;
 269 }
 270
 271 /* Extract the function calling convention from MANGLED and
 272    return 1 on success or 0 on failure.  */
 273 static int
 274 dlang_call_convention_p (const char *mangled)
 275 {
 276   switch (*mangled)
 277     {
 278     case 'F': case 'U': case 'V':
 279     case 'W': case 'R': case 'Y':
 280       return 1;
 281
 282     default:
 283       return 0;
 284     }
 285 }
 286
 287 /* Extract the back reference position from MANGLED, and assign the result
 288    to RET.  Return the remaining string on success or NULL on failure.
 289    A result <= 0 is a failure.  */
 290 static const char *
 291 dlang_decode_backref (const char *mangled, long *ret)
 292 {
 293   /* Return NULL if trying to extract something that isn't a digit.  */
 294   if (mangled == NULL || !ISALPHA (*mangled))
 295     return NULL;
 296
 297   /* Any identifier or non-basic type that has been emitted to the mangled
 298      symbol before will not be emitted again, but is referenced by a special
 299      sequence encoding the relative position of the original occurrence in the
 300      mangled symbol name.
 301
 302      Numbers in back references are encoded with base 26 by upper case letters
 303      A-Z for higher digits but lower case letters a-z for the last digit.
 304
 305         NumberBackRef:
 306             [a-z]
 307             [A-Z] NumberBackRef
 308             ^
 309    */
 310   unsigned long val = 0;
 311
 312   while (ISALPHA (*mangled))
 313     {
 314       /* Check for overflow.  */
 315       if (val > (ULONG_MAX - 25) / 26)
 316         break;
 317
 318       val *= 26;
 319
 320       if (mangled[0] >= 'a' && mangled[0] <= 'z')
 321         {
 322           val += mangled[0] - 'a';
 323           if ((long) val <= 0)
 324             break;
 325           *ret = val;
 326           return mangled + 1;
 327         }
 328
 329       val += mangled[0] - 'A';
 330       mangled++;
 331     }
 332
 333   return NULL;
 334 }
 335
 336 /* Extract the symbol pointed at by the back reference and assign the result
 337    to RET.  Return the remaining string on success or NULL on failure.  */
 338 static const char *
 339 dlang_backref (const char *mangled, const char **ret, struct dlang_info *info)
 340 {
 341   *ret = NULL;
 342
 343   if (mangled == NULL || *mangled != 'Q')
 344     return NULL;
 345
 346   /* Position of 'Q'.  */
 347   const char *qpos = mangled;
 348   long refpos;
 349   mangled++;
 350
 351   mangled = dlang_decode_backref (mangled, &refpos);
 352   if (mangled == NULL)
 353     return NULL;
 354
 355   if (refpos > qpos - info->s)
 356     return NULL;
 357
 358   /* Set the position of the back reference.  */
 359   *ret = qpos - refpos;
 360
 361   return mangled;
 362 }
 363
 364 /* Demangle a back referenced symbol from MANGLED and append it to DECL.
 365    Return the remaining string on success or NULL on failure.  */
 366 static const char *
 367 dlang_symbol_backref (string *decl, const char *mangled,
 368                       struct dlang_info *info)
 369 {
 370   /* An identifier back reference always points to a digit 0 to 9.
 371
 372         IdentifierBackRef:
 373             Q NumberBackRef
 374             ^
 375    */
 376   const char *backref;
 377   unsigned long len;
 378
 379   /* Get position of the back reference.  */
 380   mangled = dlang_backref (mangled, &backref, info);
 381
 382   /* Must point to a simple identifier.  */
 383   backref = dlang_number (backref, &len);
 384   if (backref == NULL || strlen(backref) < len)
 385     return NULL;
 386
 387   backref = dlang_lname (decl, backref, len);
 388   if (backref == NULL)
 389     return NULL;
 390
 391   return mangled;
 392 }
 393
 394 /* Demangle a back referenced type from MANGLED and append it to DECL.
 395    IS_FUNCTION is 1 if the back referenced type is expected to be a function.
 396    Return the remaining string on success or NULL on failure.  */
 397 static const char *
 398 dlang_type_backref (string *decl, const char *mangled, struct dlang_info *info,
 399                     int is_function)
 400 {
 401   /* A type back reference always points to a letter.
 402
 403         TypeBackRef:
 404             Q NumberBackRef
 405             ^
 406    */
 407   const char *backref;
 408
 409   /* If we appear to be moving backwards through the mangle string, then
 410      bail as this may be a recursive back reference.  */
 411   if (mangled - info->s >= info->last_backref)
 412     return NULL;
 413
 414   int save_refpos = info->last_backref;
 415   info->last_backref = mangled - info->s;
 416
 417   /* Get position of the back reference.  */
 418   mangled = dlang_backref (mangled, &backref, info);
 419
 420   /* Must point to a type.  */
 421   if (is_function)
 422     backref = dlang_function_type (decl, backref, info);
 423   else
 424     backref = dlang_type (decl, backref, info);
 425
 426   info->last_backref = save_refpos;
 427
 428   if (backref == NULL)
 429     return NULL;
 430
 431   return mangled;
 432 }
 433
 434 /* Extract the beginning of a symbol name from MANGLED and
 435    return 1 on success or 0 on failure.  */
 436 static int
 437 dlang_symbol_name_p (const char *mangled, struct dlang_info *info)
 438 {
 439   long ret;
 440   const char *qref = mangled;
 441
 442   if (ISDIGIT (*mangled))
 443     return 1;
 444
 445   if (mangled[0] == '_' && mangled[1] == '_'
 446       && (mangled[2] == 'T' || mangled[2] == 'U'))
 447     return 1;
 448
 449   if (*mangled != 'Q')
 450     return 0;
 451
 452   mangled = dlang_decode_backref (mangled + 1, &ret);
 453   if (mangled == NULL || ret > qref - info->s)
 454     return 0;
 455
 456   return ISDIGIT (qref[-ret]);
 457 }
 458
 459 /* Demangle the calling convention from MANGLED and append it to DECL.
 460    Return the remaining string on success or NULL on failure.  */
 461 static const char *
 462 dlang_call_convention (string *decl, const char *mangled)
 463 {
 464   if (mangled == NULL || *mangled == '\0')
 465     return NULL;
 466
 467   switch (*mangled)
 468     {
 469     case 'F': /* (D) */
 470       mangled++;
 471       break;
 472     case 'U': /* (C) */
 473       mangled++;
 474       string_append (decl, "extern(C) ");
 475       break;
 476     case 'W': /* (Windows) */
 477       mangled++;
 478       string_append (decl, "extern(Windows) ");
 479       break;
 480     case 'V': /* (Pascal) */
 481       mangled++;
 482       string_append (decl, "extern(Pascal) ");
 483       break;
 484     case 'R': /* (C++) */
 485       mangled++;
 486       string_append (decl, "extern(C++) ");
 487       break;
 488     case 'Y': /* (Objective-C) */
 489       mangled++;
 490       string_append (decl, "extern(Objective-C) ");
 491       break;
 492     default:
 493       return NULL;
 494     }
 495
 496   return mangled;
 497 }
 498
 499 /* Extract the type modifiers from MANGLED and append them to DECL.
 500    Returns the remaining signature on success or NULL on failure.  */
 501 static const char *
 502 dlang_type_modifiers (string *decl, const char *mangled)
 503 {
 504   if (mangled == NULL || *mangled == '\0')
 505     return NULL;
 506
 507   switch (*mangled)
 508     {
 509     case 'x': /* const */
 510       mangled++;
 511       string_append (decl, " const");
 512       return mangled;
 513     case 'y': /* immutable */
 514       mangled++;
 515       string_append (decl, " immutable");
 516       return mangled;
 517     case 'O': /* shared */
 518       mangled++;
 519       string_append (decl, " shared");
 520       return dlang_type_modifiers (decl, mangled);
 521     case 'N':
 522       mangled++;
 523       if (*mangled == 'g') /* wild */
 524         {
 525           mangled++;
 526           string_append (decl, " inout");
 527           return dlang_type_modifiers (decl, mangled);
 528         }
 529       else
 530         return NULL;
 531
 532     default:
 533       return mangled;
 534     }
 535 }
 536
 537 /* Demangle the D function attributes from MANGLED and append it to DECL.
 538    Return the remaining string on success or NULL on failure.  */
 539 static const char *
 540 dlang_attributes (string *decl, const char *mangled)
 541 {
 542   if (mangled == NULL || *mangled == '\0')
 543     return NULL;
 544
 545   while (*mangled == 'N')
 546     {
 547       mangled++;
 548       switch (*mangled)
 549         {
 550         case 'a': /* pure */
 551           mangled++;
 552           string_append (decl, "pure ");
 553           continue;
 554         case 'b': /* nothrow */
 555           mangled++;
 556           string_append (decl, "nothrow ");
 557           continue;
 558         case 'c': /* ref */
 559           mangled++;
 560           string_append (decl, "ref ");
 561           continue;
 562         case 'd': /* @property */
 563           mangled++;
 564           string_append (decl, "@property ");
 565           continue;
 566         case 'e': /* @trusted */
 567           mangled++;
 568           string_append (decl, "@trusted ");
 569           continue;
 570         case 'f': /* @safe */
 571           mangled++;
 572           string_append (decl, "@safe ");
 573           continue;
 574         case 'g':
 575         case 'h':
 576         case 'k':
 577         case 'n':
 578           /* inout parameter is represented as 'Ng'.
 579              vector parameter is represented as 'Nh'.
 580              return parameter is represented as 'Nk'.
 581              typeof(*null) parameter is represented as 'Nn'.
 582              If we see this, then we know we're really in the
 583              parameter list.  Rewind and break.  */
 584           mangled--;
 585           break;
 586         case 'i': /* @nogc */
 587           mangled++;
 588           string_append (decl, "@nogc ");
 589           continue;
 590         case 'j': /* return */
 591           mangled++;
 592           string_append (decl, "return ");
 593           continue;
 594         case 'l': /* scope */
 595           mangled++;
 596           string_append (decl, "scope ");
 597           continue;
 598         case 'm': /* @live */
 599           mangled++;
 600           string_append (decl, "@live ");
 601           continue;
 602
 603         default: /* unknown attribute */
 604           return NULL;
 605         }
 606       break;
 607     }
 608
 609   return mangled;
 610 }
 611
 612 /* Demangle the function type from MANGLED without the return type.
 613    The arguments are appended to ARGS, the calling convention is appended
 614    to CALL and attributes are appended to ATTR.  Any of these can be NULL
 615    to throw the information away.  Return the remaining string on success
 616    or NULL on failure.  */
 617 static const char *
 618 dlang_function_type_noreturn (string *args, string *call, string *attr,
 619                               const char *mangled, struct dlang_info *info)
 620 {
 621   string dump;
 622   string_init (&dump);
 623
 624   /* Skip over calling convention and attributes.  */
 625   mangled = dlang_call_convention (call ? call : &dump, mangled);
 626   mangled = dlang_attributes (attr ? attr : &dump, mangled);
 627
 628   if (args)
 629     string_append (args, "(");
 630
 631   mangled = dlang_function_args (args ? args : &dump, mangled, info);
 632   if (args)
 633     string_append (args, ")");
 634
 635   string_delete (&dump);
 636   return mangled;
 637 }
 638
 639 /* Demangle the function type from MANGLED and append it to DECL.
 640    Return the remaining string on success or NULL on failure.  */
 641 static const char *
 642 dlang_function_type (string *decl, const char *mangled, struct dlang_info *info)
 643 {
 644   string attr, args, type;
 645
 646   if (mangled == NULL || *mangled == '\0')
 647     return NULL;
 648
 649   /* The order of the mangled string is:
 650         CallConvention FuncAttrs Arguments ArgClose Type
 651
 652      The demangled string is re-ordered as:
 653         CallConvention Type Arguments FuncAttrs
 654    */
 655   string_init (&attr);
 656   string_init (&args);
 657   string_init (&type);
 658
 659   mangled = dlang_function_type_noreturn (&args, decl, &attr, mangled, info);
 660
 661   /* Function return type.  */
 662   mangled = dlang_type (&type, mangled, info);
 663
 664   /* Append to decl in order. */
 665   string_appendn (decl, type.b, string_length (&type));
 666   string_appendn (decl, args.b, string_length (&args));
 667   string_append (decl, " ");
 668   string_appendn (decl, attr.b, string_length (&attr));
 669
 670   string_delete (&attr);
 671   string_delete (&args);
 672   string_delete (&type);
 673   return mangled;
 674 }
 675
 676 /* Demangle the argument list from MANGLED and append it to DECL.
 677    Return the remaining string on success or NULL on failure.  */
 678 static const char *
 679 dlang_function_args (string *decl, const char *mangled, struct dlang_info *info)
 680 {
 681   size_t n = 0;
 682
 683   while (mangled && *mangled != '\0')
 684     {
 685       switch (*mangled)
 686         {
 687         case 'X': /* (variadic T t...) style.  */
 688           mangled++;
 689           string_append (decl, "...");
 690           return mangled;
 691         case 'Y': /* (variadic T t, ...) style.  */
 692           mangled++;
 693           if (n != 0)
 694             string_append (decl, ", ");
 695           string_append (decl, "...");
 696           return mangled;
 697         case 'Z': /* Normal function.  */
 698           mangled++;
 699           return mangled;
 700         }
 701
 702       if (n++)
 703         string_append (decl, ", ");
 704
 705       if (*mangled == 'M') /* scope(T) */
 706         {
 707           mangled++;
 708           string_append (decl, "scope ");
 709         }
 710
 711       if (mangled[0] == 'N' && mangled[1] == 'k') /* return(T) */
 712         {
 713           mangled += 2;
 714           string_append (decl, "return ");
 715         }
 716
 717       switch (*mangled)
 718         {
 719         case 'I': /* in(T) */
 720           mangled++;
 721           string_append (decl, "in ");
 722           if (*mangled == 'K') /* in ref(T) */
 723             {
 724               mangled++;
 725               string_append (decl, "ref ");
 726             }
 727           break;
 728         case 'J': /* out(T) */
 729           mangled++;
 730           string_append (decl, "out ");
 731           break;
 732         case 'K': /* ref(T) */
 733           mangled++;
 734           string_append (decl, "ref ");
 735           break;
 736         case 'L': /* lazy(T) */
 737           mangled++;
 738           string_append (decl, "lazy ");
 739           break;
 740         }
 741       mangled = dlang_type (decl, mangled, info);
 742     }
 743
 744   return mangled;
 745 }
 746
 747 /* Demangle the type from MANGLED and append it to DECL.
 748    Return the remaining string on success or NULL on failure.  */
 749 static const char *
 750 dlang_type (string *decl, const char *mangled, struct dlang_info *info)
 751 {
 752   if (mangled == NULL || *mangled == '\0')
 753     return NULL;
 754
 755   switch (*mangled)
 756     {
 757     case 'O': /* shared(T) */
 758       mangled++;
 759       string_append (decl, "shared(");
 760       mangled = dlang_type (decl, mangled, info);
 761       string_append (decl, ")");
 762       return mangled;
 763     case 'x': /* const(T) */
 764       mangled++;
 765       string_append (decl, "const(");
 766       mangled = dlang_type (decl, mangled, info);
 767       string_append (decl, ")");
 768       return mangled;
 769     case 'y': /* immutable(T) */
 770       mangled++;
 771       string_append (decl, "immutable(");
 772       mangled = dlang_type (decl, mangled, info);
 773       string_append (decl, ")");
 774       return mangled;
 775     case 'N':
 776       mangled++;
 777       if (*mangled == 'g') /* wild(T) */
 778         {
 779           mangled++;
 780           string_append (decl, "inout(");
 781           mangled = dlang_type (decl, mangled, info);
 782           string_append (decl, ")");
 783           return mangled;
 784         }
 785       else if (*mangled == 'h') /* vector(T) */
 786         {
 787           mangled++;
 788           string_append (decl, "__vector(");
 789           mangled = dlang_type (decl, mangled, info);
 790           string_append (decl, ")");
 791           return mangled;
 792         }
 793       else if (*mangled == 'n') /* typeof(*null) */
 794         {
 795           mangled++;
 796           string_append (decl, "typeof(*null)");
 797           return mangled;
 798         }
 799       else
 800         return NULL;
 801     case 'A': /* dynamic array (T[]) */
 802       mangled++;
 803       mangled = dlang_type (decl, mangled, info);
 804       string_append (decl, "[]");
 805       return mangled;
 806     case 'G': /* static array (T[N]) */
 807     {
 808       const char *numptr;
 809       size_t num = 0;
 810       mangled++;
 811
 812       numptr = mangled;
 813       while (ISDIGIT (*mangled))
 814         {
 815           num++;
 816           mangled++;
 817         }
 818       mangled = dlang_type (decl, mangled, info);
 819       string_append (decl, "[");
 820       string_appendn (decl, numptr, num);
 821       string_append (decl, "]");
 822       return mangled;
 823     }
 824     case 'H': /* associative array (T[T]) */
 825     {
 826       string type;
 827       size_t sztype;
 828       mangled++;
 829
 830       string_init (&type);
 831       mangled = dlang_type (&type, mangled, info);
 832       sztype = string_length (&type);
 833
 834       mangled = dlang_type (decl, mangled, info);
 835       string_append (decl, "[");
 836       string_appendn (decl, type.b, sztype);
 837       string_append (decl, "]");
 838
 839       string_delete (&type);
 840       return mangled;
 841     }
 842     case 'P': /* pointer (T*) */
 843       mangled++;
 844       if (!dlang_call_convention_p (mangled))
 845         {
 846           mangled = dlang_type (decl, mangled, info);
 847           string_append (decl, "*");
 848           return mangled;
 849         }
 850       /* Fall through */
 851     case 'F': /* function T (D) */
 852     case 'U': /* function T (C) */
 853     case 'W': /* function T (Windows) */
 854     case 'V': /* function T (Pascal) */
 855     case 'R': /* function T (C++) */
 856     case 'Y': /* function T (Objective-C) */
 857       /* Function pointer types don't include the trailing asterisk.  */
 858       mangled = dlang_function_type (decl, mangled, info);
 859       string_append (decl, "function");
 860       return mangled;
 861     case 'C': /* class T */
 862     case 'S': /* struct T */
 863     case 'E': /* enum T */
 864     case 'T': /* typedef T */
 865       mangled++;
 866       return dlang_parse_qualified (decl, mangled, info, 0);
 867     case 'D': /* delegate T */
 868     {
 869       string mods;
 870       size_t szmods;
 871       mangled++;
 872
 873       string_init (&mods);
 874       mangled = dlang_type_modifiers (&mods, mangled);
 875       szmods = string_length (&mods);
 876
 877       /* Back referenced function type.  */
 878       if (mangled && *mangled == 'Q')
 879         mangled = dlang_type_backref (decl, mangled, info, 1);
 880       else
 881         mangled = dlang_function_type (decl, mangled, info);
 882
 883       string_append (decl, "delegate");
 884       string_appendn (decl, mods.b, szmods);
 885
 886       string_delete (&mods);
 887       return mangled;
 888     }
 889     case 'B': /* tuple T */
 890       mangled++;
 891       return dlang_parse_tuple (decl, mangled, info);
 892
 893     /* Basic types */
 894     case 'n':
 895       mangled++;
 896       string_append (decl, "typeof(null)");
 897       return mangled;
 898     case 'v':
 899       mangled++;
 900       string_append (decl, "void");
 901       return mangled;
 902     case 'g':
 903       mangled++;
 904       string_append (decl, "byte");
 905       return mangled;
 906     case 'h':
 907       mangled++;
 908       string_append (decl, "ubyte");
 909       return mangled;
 910     case 's':
 911       mangled++;
 912       string_append (decl, "short");
 913       return mangled;
 914     case 't':
 915       mangled++;
 916       string_append (decl, "ushort");
 917       return mangled;
 918     case 'i':
 919       mangled++;
 920       string_append (decl, "int");
 921       return mangled;
 922     case 'k':
 923       mangled++;
 924       string_append (decl, "uint");
 925       return mangled;
 926     case 'l':
 927       mangled++;
 928       string_append (decl, "long");
 929       return mangled;
 930     case 'm':
 931       mangled++;
 932       string_append (decl, "ulong");
 933       return mangled;
 934     case 'f':
 935       mangled++;
 936       string_append (decl, "float");
 937       return mangled;
 938     case 'd':
 939       mangled++;
 940       string_append (decl, "double");
 941       return mangled;
 942     case 'e':
 943       mangled++;
 944       string_append (decl, "real");
 945       return mangled;
 946
 947     /* Imaginary and Complex types */
 948     case 'o':
 949       mangled++;
 950       string_append (decl, "ifloat");
 951       return mangled;
 952     case 'p':
 953       mangled++;
 954       string_append (decl, "idouble");
 955       return mangled;
 956     case 'j':
 957       mangled++;
 958       string_append (decl, "ireal");
 959       return mangled;
 960     case 'q':
 961       mangled++;
 962       string_append (decl, "cfloat");
 963       return mangled;
 964     case 'r':
 965       mangled++;
 966       string_append (decl, "cdouble");
 967       return mangled;
 968     case 'c':
 969       mangled++;
 970       string_append (decl, "creal");
 971       return mangled;
 972
 973     /* Other types */
 974     case 'b':
 975       mangled++;
 976       string_append (decl, "bool");
 977       return mangled;
 978     case 'a':
 979       mangled++;
 980       string_append (decl, "char");
 981       return mangled;
 982     case 'u':
 983       mangled++;
 984       string_append (decl, "wchar");
 985       return mangled;
 986     case 'w':
 987       mangled++;
 988       string_append (decl, "dchar");
 989       return mangled;
 990     case 'z':
 991       mangled++;
 992       switch (*mangled)
 993         {
 994         case 'i':
 995           mangled++;
 996           string_append (decl, "cent");
 997           return mangled;
 998         case 'k':
 999           mangled++;
1000           string_append (decl, "ucent");
1001           return mangled;
1002         }
1003       return NULL;
1004
1005     /* Back referenced type.  */
1006     case 'Q':
1007       return dlang_type_backref (decl, mangled, info, 0);
1008
1009     default: /* unhandled */
1010       return NULL;
1011     }
1012 }
1013
1014 /* Extract the identifier from MANGLED and append it to DECL.
1015    Return the remaining string on success or NULL on failure.  */
1016 static const char *
1017 dlang_identifier (string *decl, const char *mangled, struct dlang_info *info)
1018 {
1019   unsigned long len;
1020
1021   if (mangled == NULL || *mangled == '\0')
1022     return NULL;
1023
1024   if (*mangled == 'Q')
1025     return dlang_symbol_backref (decl, mangled, info);
1026
1027   /* May be a template instance without a length prefix.  */
1028   if (mangled[0] == '_' && mangled[1] == '_'
1029       && (mangled[2] == 'T' || mangled[2] == 'U'))
1030     return dlang_parse_template (decl, mangled, info, TEMPLATE_LENGTH_UNKNOWN);
1031
1032   const char *endptr = dlang_number (mangled, &len);
1033
1034   if (endptr == NULL || len == 0)
1035     return NULL;
1036
1037   if (strlen (endptr) < len)
1038     return NULL;
1039
1040   mangled = endptr;
1041
1042   /* May be a template instance with a length prefix.  */
1043   if (len >= 5 && mangled[0] == '_' && mangled[1] == '_'
1044       && (mangled[2] == 'T' || mangled[2] == 'U'))
1045     return dlang_parse_template (decl, mangled, info, len);
1046
1047   /* There can be multiple different declarations in the same function that have
1048      the same mangled name.  To make the mangled names unique, a fake parent in
1049      the form `__Sddd' is added to the symbol.  */
1050   if (len >= 4 && mangled[0] == '_' && mangled[1] == '_' && mangled[2] == 'S')
1051     {
1052       const char *numptr = mangled + 3;
1053       while (numptr < (mangled + len) && ISDIGIT (*numptr))
1054         numptr++;
1055
1056       if (mangled + len == numptr)
1057         {
1058           /* Skip over the fake parent.  */
1059           mangled += len;
1060           return dlang_identifier (decl, mangled, info);
1061         }
1062
1063       /* else demangle it as a plain identifier.  */
1064     }
1065
1066   return dlang_lname (decl, mangled, len);
1067 }
1068
1069 /* Extract the plain identifier from MANGLED and prepend/append it to DECL
1070    with special treatment for some magic compiler generted symbols.
1071    Return the remaining string on success or NULL on failure.  */
1072 static const char *
1073 dlang_lname (string *decl, const char *mangled, unsigned long len)
1074 {
1075   switch (len)
1076     {
1077     case 6:
1078       if (strncmp (mangled, "__ctor", len) == 0)
1079         {
1080           /* Constructor symbol for a class/struct.  */
1081           string_append (decl, "this");
1082           mangled += len;
1083           return mangled;
1084         }
1085       else if (strncmp (mangled, "__dtor", len) == 0)
1086         {
1087           /* Destructor symbol for a class/struct.  */
1088           string_append (decl, "~this");
1089           mangled += len;
1090           return mangled;
1091         }
1092       else if (strncmp (mangled, "__initZ", len + 1) == 0)
1093         {
1094           /* The static initialiser for a given symbol.  */
1095           string_prepend (decl, "initializer for ");
1096           string_setlength (decl, string_length (decl) - 1);
1097           mangled += len;
1098           return mangled;
1099         }
1100       else if (strncmp (mangled, "__vtblZ", len + 1) == 0)
1101         {
1102           /* The vtable symbol for a given class.  */
1103           string_prepend (decl, "vtable for ");
1104           string_setlength (decl, string_length (decl) - 1);
1105           mangled += len;
1106           return mangled;
1107         }
1108       break;
1109
1110     case 7:
1111       if (strncmp (mangled, "__ClassZ", len + 1) == 0)
1112         {
1113           /* The classinfo symbol for a given class.  */
1114           string_prepend (decl, "ClassInfo for ");
1115           string_setlength (decl, string_length (decl) - 1);
1116           mangled += len;
1117           return mangled;
1118         }
1119       break;
1120
1121     case 10:
1122       if (strncmp (mangled, "__postblitMFZ", len + 3) == 0)
1123         {
1124           /* Postblit symbol for a struct.  */
1125           string_append (decl, "this(this)");
1126           mangled += len + 3;
1127           return mangled;
1128         }
1129       break;
1130
1131     case 11:
1132       if (strncmp (mangled, "__InterfaceZ", len + 1) == 0)
1133         {
1134           /* The interface symbol for a given class.  */
1135           string_prepend (decl, "Interface for ");
1136           string_setlength (decl, string_length (decl) - 1);
1137           mangled += len;
1138           return mangled;
1139         }
1140       break;
1141
1142     case 12:
1143       if (strncmp (mangled, "__ModuleInfoZ", len + 1) == 0)
1144         {
1145           /* The ModuleInfo symbol for a given module.  */
1146           string_prepend (decl, "ModuleInfo for ");
1147           string_setlength (decl, string_length (decl) - 1);
1148           mangled += len;
1149           return mangled;
1150         }
1151       break;
1152     }
1153
1154   string_appendn (decl, mangled, len);
1155   mangled += len;
1156
1157   return mangled;
1158 }
1159
1160 /* Extract the integer value from MANGLED and append it to DECL,
1161    where TYPE is the type it should be represented as.
1162    Return the remaining string on success or NULL on failure.  */
1163 static const char *
1164 dlang_parse_integer (string *decl, const char *mangled, char type)
1165 {
1166   if (type == 'a' || type == 'u' || type == 'w')
1167     {
1168       /* Parse character value.  */
1169       char value[20];
1170       int pos = sizeof(value);
1171       int width = 0;
1172       unsigned long val;
1173
1174       mangled = dlang_number (mangled, &val);
1175       if (mangled == NULL)
1176         return NULL;
1177
1178       string_append (decl, "'");
1179
1180       if (type == 'a' && val >= 0x20 && val < 0x7F)
1181         {
1182           /* Represent as a character literal.  */
1183           char c = (char) val;
1184           string_appendn (decl, &c, 1);
1185         }
1186       else
1187         {
1188           /* Represent as a hexadecimal value.  */
1189           switch (type)
1190             {
1191             case 'a': /* char */
1192               string_append (decl, "\\x");
1193               width = 2;
1194               break;
1195             case 'u': /* wchar */
1196               string_append (decl, "\\u");
1197               width = 4;
1198               break;
1199             case 'w': /* dchar */
1200               string_append (decl, "\\U");
1201               width = 8;
1202               break;
1203             }
1204
1205           while (val > 0)
1206             {
1207               int digit = val % 16;
1208
1209               if (digit < 10)
1210                 value[--pos] = (char)(digit + '0');
1211               else
1212                 value[--pos] = (char)((digit - 10) + 'a');
1213
1214               val /= 16;
1215               width--;
1216             }
1217
1218           for (; width > 0; width--)
1219             value[--pos] = '0';
1220
1221           string_appendn (decl, &(value[pos]), sizeof(value) - pos);
1222         }
1223       string_append (decl, "'");
1224     }
1225   else if (type == 'b')
1226     {
1227       /* Parse boolean value.  */
1228       unsigned long val;
1229
1230       mangled = dlang_number (mangled, &val);
1231       if (mangled == NULL)
1232         return NULL;
1233
1234       string_append (decl, val ? "true" : "false");
1235     }
1236   else
1237     {
1238       /* Parse integer value.  */
1239       const char *numptr = mangled;
1240       size_t num = 0;
1241
1242       if (! ISDIGIT (*mangled))
1243         return NULL;
1244
1245       while (ISDIGIT (*mangled))
1246         {
1247           num++;
1248           mangled++;
1249         }
1250       string_appendn (decl, numptr, num);
1251
1252       /* Append suffix.  */
1253       switch (type)
1254         {
1255         case 'h': /* ubyte */
1256         case 't': /* ushort */
1257         case 'k': /* uint */
1258           string_append (decl, "u");
1259           break;
1260         case 'l': /* long */
1261           string_append (decl, "L");
1262           break;
1263         case 'm': /* ulong */
1264           string_append (decl, "uL");
1265           break;
1266         }
1267     }
1268
1269   return mangled;
1270 }
1271
1272 /* Extract the floating-point value from MANGLED and append it to DECL.
1273    Return the remaining string on success or NULL on failure.  */
1274 static const char *
1275 dlang_parse_real (string *decl, const char *mangled)
1276 {
1277   /* Handle NAN and +-INF.  */
1278   if (strncmp (mangled, "NAN", 3) == 0)
1279     {
1280       string_append (decl, "NaN");
1281       mangled += 3;
1282       return mangled;
1283     }
1284   else if (strncmp (mangled, "INF", 3) == 0)
1285     {
1286       string_append (decl, "Inf");
1287       mangled += 3;
1288       return mangled;
1289     }
1290   else if (strncmp (mangled, "NINF", 4) == 0)
1291     {
1292       string_append (decl, "-Inf");
1293       mangled += 4;
1294       return mangled;
1295     }
1296
1297   /* Hexadecimal prefix and leading bit.  */
1298   if (*mangled == 'N')
1299     {
1300       string_append (decl, "-");
1301       mangled++;
1302     }
1303
1304   if (!ISXDIGIT (*mangled))
1305     return NULL;
1306
1307   string_append (decl, "0x");
1308   string_appendn (decl, mangled, 1);
1309   string_append (decl, ".");
1310   mangled++;
1311
1312   /* Significand.  */
1313   while (ISXDIGIT (*mangled))
1314     {
1315       string_appendn (decl, mangled, 1);
1316       mangled++;
1317     }
1318
1319   /* Exponent.  */
1320   if (*mangled != 'P')
1321     return NULL;
1322
1323   string_append (decl, "p");
1324   mangled++;
1325
1326   if (*mangled == 'N')
1327     {
1328       string_append (decl, "-");
1329       mangled++;
1330     }
1331
1332   while (ISDIGIT (*mangled))
1333     {
1334       string_appendn (decl, mangled, 1);
1335       mangled++;
1336     }
1337
1338   return mangled;
1339 }
1340
1341 /* Extract the string value from MANGLED and append it to DECL.
1342    Return the remaining string on success or NULL on failure.  */
1343 static const char *
1344 dlang_parse_string (string *decl, const char *mangled)
1345 {
1346   char type = *mangled;
1347   unsigned long len;
1348
1349   mangled++;
1350   mangled = dlang_number (mangled, &len);
1351   if (mangled == NULL || *mangled != '_')
1352     return NULL;
1353
1354   mangled++;
1355   string_append (decl, "\"");
1356   while (len--)
1357     {
1358       char val;
1359       const char *endptr = dlang_hexdigit (mangled, &val);
1360
1361       if (endptr == NULL)
1362         return NULL;
1363
1364       /* Sanitize white and non-printable characters.  */
1365       switch (val)
1366         {
1367         case ' ':
1368           string_append (decl, " ");
1369           break;
1370         case '\t':
1371           string_append (decl, "\\t");
1372           break;
1373         case '\n':
1374           string_append (decl, "\\n");
1375           break;
1376         case '\r':
1377           string_append (decl, "\\r");
1378           break;
1379         case '\f':
1380           string_append (decl, "\\f");
1381           break;
1382         case '\v':
1383           string_append (decl, "\\v");
1384           break;
1385
1386         default:
1387           if (ISPRINT (val))
1388             string_appendn (decl, &val, 1);
1389           else
1390             {
1391               string_append (decl, "\\x");
1392               string_appendn (decl, mangled, 2);
1393             }
1394         }
1395
1396       mangled = endptr;
1397     }
1398   string_append (decl, "\"");
1399
1400   if (type != 'a')
1401     string_appendn (decl, &type, 1);
1402
1403   return mangled;
1404 }
1405
1406 /* Extract the static array value from MANGLED and append it to DECL.
1407    Return the remaining string on success or NULL on failure.  */
1408 static const char *
1409 dlang_parse_arrayliteral (string *decl, const char *mangled,
1410                           struct dlang_info *info)
1411 {
1412   unsigned long elements;
1413
1414   mangled = dlang_number (mangled, &elements);
1415   if (mangled == NULL)
1416     return NULL;
1417
1418   string_append (decl, "[");
1419   while (elements--)
1420     {
1421       mangled = dlang_value (decl, mangled, NULL, '\0', info);
1422       if (mangled == NULL)
1423         return NULL;
1424
1425       if (elements != 0)
1426         string_append (decl, ", ");
1427     }
1428
1429   string_append (decl, "]");
1430   return mangled;
1431 }
1432
1433 /* Extract the associative array value from MANGLED and append it to DECL.
1434    Return the remaining string on success or NULL on failure.  */
1435 static const char *
1436 dlang_parse_assocarray (string *decl, const char *mangled,
1437                         struct dlang_info *info)
1438 {
1439   unsigned long elements;
1440
1441   mangled = dlang_number (mangled, &elements);
1442   if (mangled == NULL)
1443     return NULL;
1444
1445   string_append (decl, "[");
1446   while (elements--)
1447     {
1448       mangled = dlang_value (decl, mangled, NULL, '\0', info);
1449       if (mangled == NULL)
1450         return NULL;
1451
1452       string_append (decl, ":");
1453       mangled = dlang_value (decl, mangled, NULL, '\0', info);
1454       if (mangled == NULL)
1455         return NULL;
1456
1457       if (elements != 0)
1458         string_append (decl, ", ");
1459     }
1460
1461   string_append (decl, "]");
1462   return mangled;
1463 }
1464
1465 /* Extract the struct literal value for NAME from MANGLED and append it to DECL.
1466    Return the remaining string on success or NULL on failure.  */
1467 static const char *
1468 dlang_parse_structlit (string *decl, const char *mangled, const char *name,
1469                        struct dlang_info *info)
1470 {
1471   unsigned long args;
1472
1473   mangled = dlang_number (mangled, &args);
1474   if (mangled == NULL)
1475     return NULL;
1476
1477   if (name != NULL)
1478     string_append (decl, name);
1479
1480   string_append (decl, "(");
1481   while (args--)
1482     {
1483       mangled = dlang_value (decl, mangled, NULL, '\0', info);
1484       if (mangled == NULL)
1485         return NULL;
1486
1487       if (args != 0)
1488         string_append (decl, ", ");
1489     }
1490
1491   string_append (decl, ")");
1492   return mangled;
1493 }
1494
1495 /* Extract the value from MANGLED and append it to DECL.
1496    Return the remaining string on success or NULL on failure.  */
1497 static const char *
1498 dlang_value (string *decl, const char *mangled, const char *name, char type,
1499              struct dlang_info *info)
1500 {
1501   if (mangled == NULL || *mangled == '\0')
1502     return NULL;
1503
1504   switch (*mangled)
1505     {
1506       /* Null value.  */
1507     case 'n':
1508       mangled++;
1509       string_append (decl, "null");
1510       break;
1511
1512       /* Integral values.  */
1513     case 'N':
1514       mangled++;
1515       string_append (decl, "-");
1516       mangled = dlang_parse_integer (decl, mangled, type);
1517       break;
1518
1519     case 'i':
1520       mangled++;
1521       /* Fall through */
1522
1523       /* There really should always be an `i' before encoded numbers, but there
1524          wasn't in early versions of D2, so this case range must remain for
1525          backwards compatibility.  */
1526     case '0': case '1': case '2': case '3': case '4':
1527     case '5': case '6': case '7': case '8': case '9':
1528       mangled = dlang_parse_integer (decl, mangled, type);
1529       break;
1530
1531       /* Real value.  */
1532     case 'e':
1533       mangled++;
1534       mangled = dlang_parse_real (decl, mangled);
1535       break;
1536
1537       /* Complex value.  */
1538     case 'c':
1539       mangled++;
1540       mangled = dlang_parse_real (decl, mangled);
1541       string_append (decl, "+");
1542       if (mangled == NULL || *mangled != 'c')
1543         return NULL;
1544       mangled++;
1545       mangled = dlang_parse_real (decl, mangled);
1546       string_append (decl, "i");
1547       break;
1548
1549       /* String values.  */
1550     case 'a': /* UTF8 */
1551     case 'w': /* UTF16 */
1552     case 'd': /* UTF32 */
1553       mangled = dlang_parse_string (decl, mangled);
1554       break;
1555
1556       /* Array values.  */
1557     case 'A':
1558       mangled++;
1559       if (type == 'H')
1560         mangled = dlang_parse_assocarray (decl, mangled, info);
1561       else
1562         mangled = dlang_parse_arrayliteral (decl, mangled, info);
1563       break;
1564
1565       /* Struct values.  */
1566     case 'S':
1567       mangled++;
1568       mangled = dlang_parse_structlit (decl, mangled, name, info);
1569       break;
1570
1571       /* Function literal symbol.  */
1572     case 'f':
1573       mangled++;
1574       if (strncmp (mangled, "_D", 2) != 0
1575           || !dlang_symbol_name_p (mangled + 2, info))
1576         return NULL;
1577       mangled = dlang_parse_mangle (decl, mangled, info);
1578       break;
1579
1580     default:
1581       return NULL;
1582     }
1583
1584   return mangled;
1585 }
1586
1587 /* Extract and demangle the symbol in MANGLED and append it to DECL.
1588    Returns the remaining signature on success or NULL on failure.  */
1589 static const char *
1590 dlang_parse_mangle (string *decl, const char *mangled, struct dlang_info *info)
1591 {
1592   /* A D mangled symbol is comprised of both scope and type information.
1593
1594         MangleName:
1595             _D QualifiedName Type
1596             _D QualifiedName Z
1597             ^
1598      The caller should have guaranteed that the start pointer is at the
1599      above location.
1600      Note that type is never a function type, but only the return type of
1601      a function or the type of a variable.
1602    */
1603   mangled += 2;
1604
1605   mangled = dlang_parse_qualified (decl, mangled, info, 1);
1606
1607   if (mangled != NULL)
1608     {
1609       /* Artificial symbols end with 'Z' and have no type.  */
1610       if (*mangled == 'Z')
1611         mangled++;
1612       else
1613         {
1614           /* Discard the declaration or return type.  */
1615           string type;
1616
1617           string_init (&type);
1618           mangled = dlang_type (&type, mangled, info);
1619           string_delete (&type);
1620         }
1621     }
1622
1623   return mangled;
1624 }
1625
1626 /* Extract and demangle the qualified symbol in MANGLED and append it to DECL.
1627    SUFFIX_MODIFIERS is 1 if we are printing modifiers on this after the symbol.
1628    Returns the remaining signature on success or NULL on failure.  */
1629 static const char *
1630 dlang_parse_qualified (string *decl, const char *mangled,
1631                        struct dlang_info *info, int suffix_modifiers)
1632 {
1633   /* Qualified names are identifiers separated by their encoded length.
1634      Nested functions also encode their argument types without specifying
1635      what they return.
1636
1637         QualifiedName:
1638             SymbolFunctionName
1639             SymbolFunctionName QualifiedName
1640             ^
1641
1642         SymbolFunctionName:
1643             SymbolName
1644             SymbolName TypeFunctionNoReturn
1645             SymbolName M TypeFunctionNoReturn
1646             SymbolName M TypeModifiers TypeFunctionNoReturn
1647
1648      The start pointer should be at the above location.
1649    */
1650   size_t n = 0;
1651   do
1652     {
1653       /* Skip over anonymous symbols.  */
1654       if (*mangled == '0')
1655       {
1656         do
1657           mangled++;
1658         while (*mangled == '0');
1659
1660         continue;
1661       }
1662
1663       if (n++)
1664         string_append (decl, ".");
1665
1666       mangled = dlang_identifier (decl, mangled, info);
1667
1668       /* Consume the encoded arguments.  However if this is not followed by the
1669          next encoded length or mangle type, then this is not a continuation of
1670          a qualified name, in which case we backtrack and return the current
1671          unconsumed position of the mangled decl.  */
1672       if (mangled && (*mangled == 'M' || dlang_call_convention_p (mangled)))
1673         {
1674           string mods;
1675           const char *start = mangled;
1676           int saved = string_length (decl);
1677
1678           /* Save the type modifiers for appending at the end if needed.  */
1679           string_init (&mods);
1680
1681           /* Skip over 'this' parameter and type modifiers.  */
1682           if (*mangled == 'M')
1683             {
1684               mangled++;
1685               mangled = dlang_type_modifiers (&mods, mangled);
1686               string_setlength (decl, saved);
1687             }
1688
1689           mangled = dlang_function_type_noreturn (decl, NULL, NULL,
1690                                                   mangled, info);
1691           if (suffix_modifiers)
1692             string_appendn (decl, mods.b, string_length (&mods));
1693
1694           if (mangled == NULL || *mangled == '\0')
1695             {
1696               /* Did not match the rule we were looking for.  */
1697               mangled = start;
1698               string_setlength (decl, saved);
1699             }
1700
1701           string_delete (&mods);
1702         }
1703     }
1704   while (mangled && dlang_symbol_name_p (mangled, info));
1705
1706   return mangled;
1707 }
1708
1709 /* Demangle the tuple from MANGLED and append it to DECL.
1710    Return the remaining string on success or NULL on failure.  */
1711 static const char *
1712 dlang_parse_tuple (string *decl, const char *mangled, struct dlang_info *info)
1713 {
1714   unsigned long elements;
1715
1716   mangled = dlang_number (mangled, &elements);
1717   if (mangled == NULL)
1718     return NULL;
1719
1720   string_append (decl, "Tuple!(");
1721
1722   while (elements--)
1723     {
1724       mangled = dlang_type (decl, mangled, info);
1725       if (mangled == NULL)
1726         return NULL;
1727
1728       if (elements != 0)
1729         string_append (decl, ", ");
1730     }
1731
1732   string_append (decl, ")");
1733   return mangled;
1734 }
1735
1736 /* Demangle the template symbol parameter from MANGLED and append it to DECL.
1737    Return the remaining string on success or NULL on failure.  */
1738 static const char *
1739 dlang_template_symbol_param (string *decl, const char *mangled,
1740                              struct dlang_info *info)
1741 {
1742   if (strncmp (mangled, "_D", 2) == 0
1743       && dlang_symbol_name_p (mangled + 2, info))
1744     return dlang_parse_mangle (decl, mangled, info);
1745
1746   if (*mangled == 'Q')
1747     return dlang_parse_qualified (decl, mangled, info, 0);
1748
1749   unsigned long len;
1750   const char *endptr = dlang_number (mangled, &len);
1751
1752   if (endptr == NULL || len == 0)
1753     return NULL;
1754
1755   /* In template parameter symbols generated by the frontend up to 2.076,
1756      the symbol length is encoded and the first character of the mangled
1757      name can be a digit.  This causes ambiguity issues because the digits
1758      of the two numbers are adjacent.  */
1759   long psize = len;
1760   const char *pend;
1761   int saved = string_length (decl);
1762
1763   /* Work backwards until a match is found.  */
1764   for (pend = endptr; endptr != NULL; pend--)
1765     {
1766       mangled = pend;
1767
1768       /* Reached the beginning of the pointer to the name length,
1769          try parsing the entire symbol.  */
1770       if (psize == 0)
1771         {
1772           psize = len;
1773           pend = endptr;
1774           endptr = NULL;
1775         }
1776
1777       /* Check whether template parameter is a function with a valid
1778          return type or an untyped identifier.  */
1779       if (dlang_symbol_name_p (mangled, info))
1780         mangled = dlang_parse_qualified (decl, mangled, info, 0);
1781       else if (strncmp (mangled, "_D", 2) == 0
1782                && dlang_symbol_name_p (mangled + 2, info))
1783         mangled = dlang_parse_mangle (decl, mangled, info);
1784
1785       /* Check for name length mismatch.  */
1786       if (mangled && (endptr == NULL || (mangled - pend) == psize))
1787         return mangled;
1788
1789       psize /= 10;
1790       string_setlength (decl, saved);
1791     }
1792
1793   /* No match on any combinations.  */
1794   return NULL;
1795 }
1796
1797 /* Demangle the argument list from MANGLED and append it to DECL.
1798    Return the remaining string on success or NULL on failure.  */
1799 static const char *
1800 dlang_template_args (string *decl, const char *mangled, struct dlang_info *info)
1801 {
1802   size_t n = 0;
1803
1804   while (mangled && *mangled != '\0')
1805     {
1806       switch (*mangled)
1807         {
1808         case 'Z': /* End of parameter list.  */
1809           mangled++;
1810           return mangled;
1811         }
1812
1813       if (n++)
1814         string_append (decl, ", ");
1815
1816       /* Skip over specialised template prefix.  */
1817       if (*mangled == 'H')
1818         mangled++;
1819
1820       switch (*mangled)
1821         {
1822         case 'S': /* Symbol parameter.  */
1823           mangled++;
1824           mangled = dlang_template_symbol_param (decl, mangled, info);
1825           break;
1826         case 'T': /* Type parameter.  */
1827           mangled++;
1828           mangled = dlang_type (decl, mangled, info);
1829           break;
1830         case 'V': /* Value parameter.  */
1831         {
1832           string name;
1833           char type;
1834
1835           /* Peek at the type.  */
1836           mangled++;
1837           type = *mangled;
1838
1839           if (type == 'Q')
1840             {
1841               /* Value type is a back reference, peek at the real type.  */
1842               const char *backref;
1843               if (dlang_backref (mangled, &backref, info) == NULL)
1844                 return NULL;
1845
1846               type = *backref;
1847             }
1848
1849           /* In the few instances where the type is actually desired in
1850              the output, it should precede the value from dlang_value.  */
1851           string_init (&name);
1852           mangled = dlang_type (&name, mangled, info);
1853           string_need (&name, 1);
1854           *(name.p) = '\0';
1855
1856           mangled = dlang_value (decl, mangled, name.b, type, info);
1857           string_delete (&name);
1858           break;
1859         }
1860         case 'X': /* Externally mangled parameter.  */
1861         {
1862           unsigned long len;
1863           const char *endptr;
1864
1865           mangled++;
1866           endptr = dlang_number (mangled, &len);
1867           if (endptr == NULL || strlen (endptr) < len)
1868             return NULL;
1869
1870           string_appendn (decl, endptr, len);
1871           mangled = endptr + len;
1872           break;
1873         }
1874         default:
1875           return NULL;
1876         }
1877     }
1878
1879   return mangled;
1880 }
1881
1882 /* Extract and demangle the template symbol in MANGLED, expected to
1883    be made up of LEN characters (-1 if unknown), and append it to DECL.
1884    Returns the remaining signature on success or NULL on failure.  */
1885 static const char *
1886 dlang_parse_template (string *decl, const char *mangled,
1887                       struct dlang_info *info, unsigned long len)
1888 {
1889   const char *start = mangled;
1890   string args;
1891
1892   /* Template instance names have the types and values of its parameters
1893      encoded into it.
1894
1895         TemplateInstanceName:
1896             Number __T LName TemplateArgs Z
1897             Number __U LName TemplateArgs Z
1898                    ^
1899      The start pointer should be at the above location, and LEN should be
1900      the value of the decoded number.
1901    */
1902
1903   /* Template symbol.  */
1904   if (!dlang_symbol_name_p (mangled + 3, info) || mangled[3] == '0')
1905     return NULL;
1906
1907   mangled += 3;
1908
1909   /* Template identifier.  */
1910   mangled = dlang_identifier (decl, mangled, info);
1911
1912   /* Template arguments.  */
1913   string_init (&args);
1914   mangled = dlang_template_args (&args, mangled, info);
1915
1916   string_append (decl, "!(");
1917   string_appendn (decl, args.b, string_length (&args));
1918   string_append (decl, ")");
1919
1920   string_delete (&args);
1921
1922   /* Check for template name length mismatch.  */
1923   if (len != TEMPLATE_LENGTH_UNKNOWN
1924       && mangled
1925       && (unsigned long) (mangled - start) != len)
1926     return NULL;
1927
1928   return mangled;
1929 }
1930
1931 /* Initialize the information structure we use to pass around information.  */
1932 static void
1933 dlang_demangle_init_info (const char *mangled, int last_backref,
1934                           struct dlang_info *info)
1935 {
1936   info->s = mangled;
1937   info->last_backref = last_backref;
1938 }
1939
1940 /* Extract and demangle the symbol in MANGLED.  Returns the demangled
1941    signature on success or NULL on failure.  */
1942
1943 char *
1944 dlang_demangle (const char *mangled, int option ATTRIBUTE_UNUSED)
1945 {
1946   string decl;
1947   char *demangled = NULL;
1948
1949   if (mangled == NULL || *mangled == '\0')
1950     return NULL;
1951
1952   if (strncmp (mangled, "_D", 2) != 0)
1953     return NULL;
1954
1955   string_init (&decl);
1956
1957   if (strcmp (mangled, "_Dmain") == 0)
1958     {
1959       string_append (&decl, "D main");
1960     }
1961   else
1962     {
1963       struct dlang_info info;
1964
1965       dlang_demangle_init_info (mangled, strlen (mangled), &info);
1966       mangled = dlang_parse_mangle (&decl, mangled, &info);
1967
1968       /* Check that the entire symbol was successfully demangled.  */
1969       if (mangled == NULL || *mangled != '\0')
1970         string_delete (&decl);
1971     }
1972
1973   if (string_length (&decl) > 0)
1974     {
1975       string_need (&decl, 1);
1976       *(decl.p) = '\0';
1977       demangled = decl.b;
1978     }
1979
1980   return demangled;
1981 }
1982