src/doc.c

   1 /* Record indices of function doc strings stored in a file.
   2
   3 Copyright (C) 1985-1986, 1993-1995, 1997-2015 Free Software Foundation,
   4 Inc.
   5
   6 This file is part of GNU Emacs.
   7
   8 GNU Emacs is free software: you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation, either version 3 of the License, or
  11 (at your option) any later version.
  12
  13 GNU Emacs is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21
  22 #include <config.h>
  23
  24 #include <errno.h>
  25 #include <sys/types.h>
  26 #include <sys/file.h>   /* Must be after sys/types.h for USG.  */
  27 #include <fcntl.h>
  28 #include <unistd.h>
  29
  30 #include <c-ctype.h>
  31
  32 #include "lisp.h"
  33 #include "character.h"
  34 #include "buffer.h"
  35 #include "keyboard.h"
  36 #include "keymap.h"
  37
  38 Lisp_Object Qfunction_documentation;
  39
  40 /* Buffer used for reading from documentation file.  */
  41 static char *get_doc_string_buffer;
  42 static ptrdiff_t get_doc_string_buffer_size;
  43
  44 static unsigned char *read_bytecode_pointer;
  45
  46 /* `readchar' in lread.c calls back here to fetch the next byte.
  47    If UNREADFLAG is 1, we unread a byte.  */
  48
  49 int
  50 read_bytecode_char (bool unreadflag)
  51 {
  52   if (unreadflag)
  53     {
  54       read_bytecode_pointer--;
  55       return 0;
  56     }
  57   return *read_bytecode_pointer++;
  58 }
  59
  60 /* Extract a doc string from a file.  FILEPOS says where to get it.
  61    If it is an integer, use that position in the standard DOC file.
  62    If it is (FILE . INTEGER), use FILE as the file name
  63    and INTEGER as the position in that file.
  64    But if INTEGER is negative, make it positive.
  65    (A negative integer is used for user variables, so we can distinguish
  66    them without actually fetching the doc string.)
  67
  68    If the location does not point to the beginning of a docstring
  69    (e.g. because the file has been modified and the location is stale),
  70    return nil.
  71
  72    If UNIBYTE, always make a unibyte string.
  73
  74    If DEFINITION, assume this is for reading
  75    a dynamic function definition; convert the bytestring
  76    and the constants vector with appropriate byte handling,
  77    and return a cons cell.  */
  78
  79 Lisp_Object
  80 get_doc_string (Lisp_Object filepos, bool unibyte, bool definition)
  81 {
  82   char *from, *to, *name, *p, *p1;
  83   int fd;
  84   ptrdiff_t minsize;
  85   int offset;
  86   EMACS_INT position;
  87   Lisp_Object file, tem, pos;
  88   ptrdiff_t count;
  89   USE_SAFE_ALLOCA;
  90
  91   if (INTEGERP (filepos))
  92     {
  93       file = Vdoc_file_name;
  94       pos = filepos;
  95     }
  96   else if (CONSP (filepos))
  97     {
  98       file = XCAR (filepos);
  99       pos = XCDR (filepos);
 100     }
 101   else
 102     return Qnil;
 103
 104   position = eabs (XINT (pos));
 105
 106   if (!STRINGP (Vdoc_directory))
 107     return Qnil;
 108
 109   if (!STRINGP (file))
 110     return Qnil;
 111
 112   /* Put the file name in NAME as a C string.
 113      If it is relative, combine it with Vdoc_directory.  */
 114
 115   tem = Ffile_name_absolute_p (file);
 116   file = ENCODE_FILE (file);
 117   if (NILP (tem))
 118     {
 119       Lisp_Object docdir = ENCODE_FILE (Vdoc_directory);
 120       minsize = SCHARS (docdir);
 121       /* sizeof ("../etc/") == 8 */
 122       if (minsize < 8)
 123         minsize = 8;
 124       name = SAFE_ALLOCA (minsize + SCHARS (file) + 8);
 125       strcpy (name, SSDATA (docdir));
 126       strcat (name, SSDATA (file));
 127     }
 128   else
 129     {
 130       name = SSDATA (file);
 131     }
 132
 133   fd = emacs_open (name, O_RDONLY, 0);
 134   if (fd < 0)
 135     {
 136 #ifndef CANNOT_DUMP
 137       if (!NILP (Vpurify_flag))
 138         {
 139           /* Preparing to dump; DOC file is probably not installed.
 140              So check in ../etc.  */
 141           strcpy (name, "../etc/");
 142           strcat (name, SSDATA (file));
 143
 144           fd = emacs_open (name, O_RDONLY, 0);
 145         }
 146 #endif
 147       if (fd < 0)
 148         {
 149           SAFE_FREE ();
 150           return concat3 (build_string ("Cannot open doc string file \""),
 151                           file, build_string ("\"\n"));
 152         }
 153     }
 154   count = SPECPDL_INDEX ();
 155   record_unwind_protect_int (close_file_unwind, fd);
 156
 157   /* Seek only to beginning of disk block.  */
 158   /* Make sure we read at least 1024 bytes before `position'
 159      so we can check the leading text for consistency.  */
 160   offset = min (position, max (1024, position % (8 * 1024)));
 161   if (TYPE_MAXIMUM (off_t) < position
 162       || lseek (fd, position - offset, 0) < 0)
 163     error ("Position %"pI"d out of range in doc string file \"%s\"",
 164            position, name);
 165
 166   /* Read the doc string into get_doc_string_buffer.
 167      P points beyond the data just read.  */
 168
 169   p = get_doc_string_buffer;
 170   while (1)
 171     {
 172       ptrdiff_t space_left = (get_doc_string_buffer_size - 1
 173                               - (p - get_doc_string_buffer));
 174       int nread;
 175
 176       /* Allocate or grow the buffer if we need to.  */
 177       if (space_left <= 0)
 178         {
 179           ptrdiff_t in_buffer = p - get_doc_string_buffer;
 180           get_doc_string_buffer
 181             = xpalloc (get_doc_string_buffer, &get_doc_string_buffer_size,
 182                        16 * 1024, -1, 1);
 183           p = get_doc_string_buffer + in_buffer;
 184           space_left = (get_doc_string_buffer_size - 1
 185                         - (p - get_doc_string_buffer));
 186         }
 187
 188       /* Read a disk block at a time.
 189          If we read the same block last time, maybe skip this?  */
 190       if (space_left > 1024 * 8)
 191         space_left = 1024 * 8;
 192       nread = emacs_read (fd, p, space_left);
 193       if (nread < 0)
 194         report_file_error ("Read error on documentation file", file);
 195       p[nread] = 0;
 196       if (!nread)
 197         break;
 198       if (p == get_doc_string_buffer)
 199         p1 = strchr (p + offset, '\037');
 200       else
 201         p1 = strchr (p, '\037');
 202       if (p1)
 203         {
 204           *p1 = 0;
 205           p = p1;
 206           break;
 207         }
 208       p += nread;
 209     }
 210   unbind_to (count, Qnil);
 211   SAFE_FREE ();
 212
 213   /* Sanity checking.  */
 214   if (CONSP (filepos))
 215     {
 216       int test = 1;
 217       /* A dynamic docstring should be either at the very beginning of a "#@
 218          comment" or right after a dynamic docstring delimiter (in case we
 219          pack several such docstrings within the same comment).  */
 220       if (get_doc_string_buffer[offset - test] != '\037')
 221         {
 222           if (get_doc_string_buffer[offset - test++] != ' ')
 223             return Qnil;
 224           while (get_doc_string_buffer[offset - test] >= '0'
 225                  && get_doc_string_buffer[offset - test] <= '9')
 226             test++;
 227           if (get_doc_string_buffer[offset - test++] != '@'
 228               || get_doc_string_buffer[offset - test] != '#')
 229             return Qnil;
 230         }
 231     }
 232   else
 233     {
 234       int test = 1;
 235       if (get_doc_string_buffer[offset - test++] != '\n')
 236         return Qnil;
 237       while (get_doc_string_buffer[offset - test] > ' ')
 238         test++;
 239       if (get_doc_string_buffer[offset - test] != '\037')
 240         return Qnil;
 241     }
 242
 243   /* Scan the text and perform quoting with ^A (char code 1).
 244      ^A^A becomes ^A, ^A0 becomes a null char, and ^A_ becomes a ^_.  */
 245   from = get_doc_string_buffer + offset;
 246   to = get_doc_string_buffer + offset;
 247   while (from != p)
 248     {
 249       if (*from == 1)
 250         {
 251           int c;
 252
 253           from++;
 254           c = *from++;
 255           if (c == 1)
 256             *to++ = c;
 257           else if (c == '0')
 258             *to++ = 0;
 259           else if (c == '_')
 260             *to++ = 037;
 261           else
 262             {
 263               unsigned char uc = c;
 264               error ("\
 265 Invalid data in documentation file -- %c followed by code %03o",
 266                      1, uc);
 267             }
 268         }
 269       else
 270         *to++ = *from++;
 271     }
 272
 273   /* If DEFINITION, read from this buffer
 274      the same way we would read bytes from a file.  */
 275   if (definition)
 276     {
 277       read_bytecode_pointer = (unsigned char *) get_doc_string_buffer + offset;
 278       return Fread (Qlambda);
 279     }
 280
 281   if (unibyte)
 282     return make_unibyte_string (get_doc_string_buffer + offset,
 283                                 to - (get_doc_string_buffer + offset));
 284   else
 285     {
 286       /* The data determines whether the string is multibyte.  */
 287       ptrdiff_t nchars
 288         = multibyte_chars_in_text (((unsigned char *) get_doc_string_buffer
 289                                     + offset),
 290                                    to - (get_doc_string_buffer + offset));
 291       return make_string_from_bytes (get_doc_string_buffer + offset,
 292                                      nchars,
 293                                      to - (get_doc_string_buffer + offset));
 294     }
 295 }
 296
 297 /* Get a string from position FILEPOS and pass it through the Lisp reader.
 298    We use this for fetching the bytecode string and constants vector
 299    of a compiled function from the .elc file.  */
 300
 301 Lisp_Object
 302 read_doc_string (Lisp_Object filepos)
 303 {
 304   return get_doc_string (filepos, 0, 1);
 305 }
 306
 307 static bool
 308 reread_doc_file (Lisp_Object file)
 309 {
 310 #if 0
 311   Lisp_Object reply, prompt[3];
 312   struct gcpro gcpro1;
 313   GCPRO1 (file);
 314   prompt[0] = build_string ("File ");
 315   prompt[1] = NILP (file) ? Vdoc_file_name : file;
 316   prompt[2] = build_string (" is out of sync.  Reload? ");
 317   reply = Fy_or_n_p (Fconcat (3, prompt));
 318   UNGCPRO;
 319   if (NILP (reply))
 320     return 0;
 321 #endif
 322
 323   if (NILP (file))
 324     Fsnarf_documentation (Vdoc_file_name);
 325   else
 326     Fload (file, Qt, Qt, Qt, Qnil);
 327
 328   return 1;
 329 }
 330
 331 DEFUN ("documentation", Fdocumentation, Sdocumentation, 1, 2, 0,
 332        doc: /* Return the documentation string of FUNCTION.
 333 Unless a non-nil second argument RAW is given, the
 334 string is passed through `substitute-command-keys'.  */)
 335   (Lisp_Object function, Lisp_Object raw)
 336 {
 337   Lisp_Object fun;
 338   Lisp_Object funcar;
 339   Lisp_Object doc;
 340   bool try_reload = 1;
 341
 342  documentation:
 343
 344   doc = Qnil;
 345
 346   if (SYMBOLP (function))
 347     {
 348       Lisp_Object tem = Fget (function, Qfunction_documentation);
 349       if (!NILP (tem))
 350         return Fdocumentation_property (function, Qfunction_documentation,
 351                                         raw);
 352     }
 353
 354   fun = Findirect_function (function, Qnil);
 355   if (CONSP (fun) && EQ (XCAR (fun), Qmacro))
 356     fun = XCDR (fun);
 357   if (SUBRP (fun))
 358     {
 359       if (XSUBR (fun)->doc == 0)
 360         return Qnil;
 361       /* FIXME: This is not portable, as it assumes that string
 362          pointers have the top bit clear.  */
 363       else if ((intptr_t) XSUBR (fun)->doc >= 0)
 364         doc = build_string (XSUBR (fun)->doc);
 365       else
 366         doc = make_number ((intptr_t) XSUBR (fun)->doc);
 367     }
 368   else if (COMPILEDP (fun))
 369     {
 370       if ((ASIZE (fun) & PSEUDOVECTOR_SIZE_MASK) <= COMPILED_DOC_STRING)
 371         return Qnil;
 372       else
 373         {
 374           Lisp_Object tem = AREF (fun, COMPILED_DOC_STRING);
 375           if (STRINGP (tem))
 376             doc = tem;
 377           else if (NATNUMP (tem) || CONSP (tem))
 378             doc = tem;
 379           else
 380             return Qnil;
 381         }
 382     }
 383   else if (STRINGP (fun) || VECTORP (fun))
 384     {
 385       return build_string ("Keyboard macro.");
 386     }
 387   else if (CONSP (fun))
 388     {
 389       funcar = XCAR (fun);
 390       if (!SYMBOLP (funcar))
 391         xsignal1 (Qinvalid_function, fun);
 392       else if (EQ (funcar, Qkeymap))
 393         return build_string ("Prefix command (definition is a keymap associating keystrokes with commands).");
 394       else if (EQ (funcar, Qlambda)
 395                || (EQ (funcar, Qclosure) && (fun = XCDR (fun), 1))
 396                || EQ (funcar, Qautoload))
 397         {
 398           Lisp_Object tem1 = Fcdr (Fcdr (fun));
 399           Lisp_Object tem = Fcar (tem1);
 400           if (STRINGP (tem))
 401             doc = tem;
 402           /* Handle a doc reference--but these never come last
 403              in the function body, so reject them if they are last.  */
 404           else if ((NATNUMP (tem) || (CONSP (tem) && INTEGERP (XCDR (tem))))
 405                    && !NILP (XCDR (tem1)))
 406             doc = tem;
 407           else
 408             return Qnil;
 409         }
 410       else
 411         goto oops;
 412     }
 413   else
 414     {
 415     oops:
 416       xsignal1 (Qinvalid_function, fun);
 417     }
 418
 419   /* If DOC is 0, it's typically because of a dumped file missing
 420      from the DOC file (bug in src/Makefile.in).  */
 421   if (EQ (doc, make_number (0)))
 422     doc = Qnil;
 423   if (INTEGERP (doc) || CONSP (doc))
 424     {
 425       Lisp_Object tem;
 426       tem = get_doc_string (doc, 0, 0);
 427       if (NILP (tem) && try_reload)
 428         {
 429           /* The file is newer, we need to reset the pointers.  */
 430           struct gcpro gcpro1, gcpro2;
 431           GCPRO2 (function, raw);
 432           try_reload = reread_doc_file (Fcar_safe (doc));
 433           UNGCPRO;
 434           if (try_reload)
 435             {
 436               try_reload = 0;
 437               goto documentation;
 438             }
 439         }
 440       else
 441         doc = tem;
 442     }
 443
 444   if (NILP (raw))
 445     doc = Fsubstitute_command_keys (doc);
 446   return doc;
 447 }
 448
 449 DEFUN ("documentation-property", Fdocumentation_property,
 450        Sdocumentation_property, 2, 3, 0,
 451        doc: /* Return the documentation string that is SYMBOL's PROP property.
 452 Third argument RAW omitted or nil means pass the result through
 453 `substitute-command-keys' if it is a string.
 454
 455 This differs from `get' in that it can refer to strings stored in the
 456 `etc/DOC' file; and that it evaluates documentation properties that
 457 aren't strings.  */)
 458   (Lisp_Object symbol, Lisp_Object prop, Lisp_Object raw)
 459 {
 460   bool try_reload = 1;
 461   Lisp_Object tem;
 462
 463  documentation_property:
 464
 465   tem = Fget (symbol, prop);
 466   if (EQ (tem, make_number (0)))
 467     tem = Qnil;
 468   if (INTEGERP (tem) || (CONSP (tem) && INTEGERP (XCDR (tem))))
 469     {
 470       Lisp_Object doc = tem;
 471       tem = get_doc_string (tem, 0, 0);
 472       if (NILP (tem) && try_reload)
 473         {
 474           /* The file is newer, we need to reset the pointers.  */
 475           struct gcpro gcpro1, gcpro2, gcpro3;
 476           GCPRO3 (symbol, prop, raw);
 477           try_reload = reread_doc_file (Fcar_safe (doc));
 478           UNGCPRO;
 479           if (try_reload)
 480             {
 481               try_reload = 0;
 482               goto documentation_property;
 483             }
 484         }
 485     }
 486   else if (!STRINGP (tem))
 487     /* Feval protects its argument.  */
 488     tem = Feval (tem, Qnil);
 489
 490   if (NILP (raw) && STRINGP (tem))
 491     tem = Fsubstitute_command_keys (tem);
 492   return tem;
 493 }
 494 \f
 495 /* Scanning the DOC files and placing docstring offsets into functions.  */
 496
 497 static void
 498 store_function_docstring (Lisp_Object obj, ptrdiff_t offset)
 499 {
 500   /* Don't use indirect_function here, or defaliases will apply their
 501      docstrings to the base functions (Bug#2603).  */
 502   Lisp_Object fun = SYMBOLP (obj) ? XSYMBOL (obj)->function : obj;
 503
 504   /* The type determines where the docstring is stored.  */
 505
 506   /* Lisp_Subrs have a slot for it.  */
 507   if (SUBRP (fun))
 508     {
 509       intptr_t negative_offset = - offset;
 510       XSUBR (fun)->doc = (char *) negative_offset;
 511     }
 512
 513   /* If it's a lisp form, stick it in the form.  */
 514   else if (CONSP (fun))
 515     {
 516       Lisp_Object tem;
 517
 518       tem = XCAR (fun);
 519       if (EQ (tem, Qlambda) || EQ (tem, Qautoload)
 520           || (EQ (tem, Qclosure) && (fun = XCDR (fun), 1)))
 521         {
 522           tem = Fcdr (Fcdr (fun));
 523           if (CONSP (tem) && INTEGERP (XCAR (tem)))
 524             /* FIXME: This modifies typically pure hash-cons'd data, so its
 525                correctness is quite delicate.  */
 526             XSETCAR (tem, make_number (offset));
 527         }
 528       else if (EQ (tem, Qmacro))
 529         store_function_docstring (XCDR (fun), offset);
 530     }
 531
 532   /* Bytecode objects sometimes have slots for it.  */
 533   else if (COMPILEDP (fun))
 534     {
 535       /* This bytecode object must have a slot for the
 536          docstring, since we've found a docstring for it.  */
 537       if ((ASIZE (fun) & PSEUDOVECTOR_SIZE_MASK) > COMPILED_DOC_STRING)
 538         ASET (fun, COMPILED_DOC_STRING, make_number (offset));
 539       else
 540         message ("No docstring slot for %s",
 541                  SYMBOLP (obj) ? SSDATA (SYMBOL_NAME (obj)) : "<anonymous>");
 542     }
 543 }
 544
 545
 546 DEFUN ("Snarf-documentation", Fsnarf_documentation, Ssnarf_documentation,
 547        1, 1, 0,
 548        doc: /* Used during Emacs initialization to scan the `etc/DOC...' file.
 549 This searches the `etc/DOC...' file for doc strings and
 550 records them in function and variable definitions.
 551 The function takes one argument, FILENAME, a string;
 552 it specifies the file name (without a directory) of the DOC file.
 553 That file is found in `../etc' now; later, when the dumped Emacs is run,
 554 the same file name is found in the `doc-directory'.  */)
 555   (Lisp_Object filename)
 556 {
 557   int fd;
 558   char buf[1024 + 1];
 559   int filled;
 560   EMACS_INT pos;
 561   Lisp_Object sym;
 562   char *p, *name;
 563   bool skip_file = 0;
 564   ptrdiff_t count;
 565   /* Preloaded defcustoms using custom-initialize-delay are added to
 566      this list, but kept unbound.  See http://debbugs.gnu.org/11565  */
 567   Lisp_Object delayed_init =
 568     find_symbol_value (intern ("custom-delayed-init-variables"));
 569
 570   if (EQ (delayed_init, Qunbound)) delayed_init = Qnil;
 571
 572   CHECK_STRING (filename);
 573
 574   if
 575 #ifndef CANNOT_DUMP
 576     (!NILP (Vpurify_flag))
 577 #else /* CANNOT_DUMP */
 578       (0)
 579 #endif /* CANNOT_DUMP */
 580     {
 581       name = alloca (SCHARS (filename) + 14);
 582       strcpy (name, "../etc/");
 583     }
 584   else
 585     {
 586       CHECK_STRING (Vdoc_directory);
 587       name = alloca (SCHARS (filename) + SCHARS (Vdoc_directory) + 1);
 588       strcpy (name, SSDATA (Vdoc_directory));
 589     }
 590   strcat (name, SSDATA (filename));     /*** Add this line ***/
 591
 592   /* Vbuild_files is nil when temacs is run, and non-nil after that.  */
 593   if (NILP (Vbuild_files))
 594     {
 595       static char const *const buildobj[] =
 596         {
 597           #include "buildobj.h"
 598         };
 599       int i = sizeof buildobj / sizeof *buildobj;
 600       while (0 <= --i)
 601         Vbuild_files = Fcons (build_string (buildobj[i]), Vbuild_files);
 602       Vbuild_files = Fpurecopy (Vbuild_files);
 603     }
 604
 605   fd = emacs_open (name, O_RDONLY, 0);
 606   if (fd < 0)
 607     {
 608       int open_errno = errno;
 609       report_file_errno ("Opening doc string file", build_string (name),
 610                          open_errno);
 611     }
 612   count = SPECPDL_INDEX ();
 613   record_unwind_protect_int (close_file_unwind, fd);
 614   Vdoc_file_name = filename;
 615   filled = 0;
 616   pos = 0;
 617   while (1)
 618     {
 619       register char *end;
 620       if (filled < 512)
 621         filled += emacs_read (fd, &buf[filled], sizeof buf - 1 - filled);
 622       if (!filled)
 623         break;
 624
 625       buf[filled] = 0;
 626       end = buf + (filled < 512 ? filled : filled - 128);
 627       p = memchr (buf, '\037', end - buf);
 628       /* p points to ^_Ffunctionname\n or ^_Vvarname\n or ^_Sfilename\n.  */
 629       if (p)
 630         {
 631           end = strchr (p, '\n');
 632
 633           /* See if this is a file name, and if it is a file in build-files.  */
 634           if (p[1] == 'S')
 635             {
 636               skip_file = 0;
 637               if (end - p > 4 && end[-2] == '.'
 638                   && (end[-1] == 'o' || end[-1] == 'c'))
 639                 {
 640                   ptrdiff_t len = end - p - 2;
 641                   char *fromfile = alloca (len + 1);
 642                   memcpy (fromfile, &p[2], len);
 643                   fromfile[len] = 0;
 644                   if (fromfile[len-1] == 'c')
 645                     fromfile[len-1] = 'o';
 646
 647                   skip_file = NILP (Fmember (build_string (fromfile),
 648                                              Vbuild_files));
 649                 }
 650             }
 651
 652           sym = oblookup (Vobarray, p + 2,
 653                           multibyte_chars_in_text ((unsigned char *) p + 2,
 654                                                    end - p - 2),
 655                           end - p - 2);
 656           /* Check skip_file so that when a function is defined several
 657              times in different files (typically, once in xterm, once in
 658              w32term, ...), we only pay attention to the one that
 659              matters.  */
 660           if (! skip_file && SYMBOLP (sym))
 661             {
 662               /* Attach a docstring to a variable?  */
 663               if (p[1] == 'V')
 664                 {
 665                   /* Install file-position as variable-documentation property
 666                      and make it negative for a user-variable
 667                      (doc starts with a `*').  */
 668                   if (!NILP (Fboundp (sym))
 669                       || !NILP (Fmemq (sym, delayed_init)))
 670                     Fput (sym, Qvariable_documentation,
 671                           make_number ((pos + end + 1 - buf)
 672                                        * (end[1] == '*' ? -1 : 1)));
 673                 }
 674
 675               /* Attach a docstring to a function?  */
 676               else if (p[1] == 'F')
 677                 {
 678                   if (!NILP (Ffboundp (sym)))
 679                     store_function_docstring (sym, pos + end + 1 - buf);
 680                 }
 681               else if (p[1] == 'S')
 682                 ; /* Just a source file name boundary marker.  Ignore it.  */
 683
 684               else
 685                 error ("DOC file invalid at position %"pI"d", pos);
 686             }
 687         }
 688       pos += end - buf;
 689       filled -= end - buf;
 690       memmove (buf, end, filled);
 691     }
 692   return unbind_to (count, Qnil);
 693 }
 694 \f
 695 DEFUN ("substitute-command-keys", Fsubstitute_command_keys,
 696        Ssubstitute_command_keys, 1, 1, 0,
 697        doc: /* Substitute key descriptions for command names in STRING.
 698 Each substring of the form \\=\\[COMMAND] is replaced by either a
 699 keystroke sequence that invokes COMMAND, or "M-x COMMAND" if COMMAND
 700 is not on any keys.
 701
 702 Each substring of the form \\=\\{MAPVAR} is replaced by a summary of
 703 the value of MAPVAR as a keymap.  This summary is similar to the one
 704 produced by `describe-bindings'.  The summary ends in two newlines
 705 \(used by the helper function `help-make-xrefs' to find the end of the
 706 summary).
 707
 708 Each substring of the form \\=\\<MAPVAR> specifies the use of MAPVAR
 709 as the keymap for future \\=\\[COMMAND] substrings.
 710 \\=\\= quotes the following character and is discarded;
 711 thus, \\=\\=\\=\\= puts \\=\\= into the output, and \\=\\=\\=\\[ puts \\=\\[ into the output.
 712
 713 Return the original STRING if no substitutions are made.
 714 Otherwise, return a new string.  */)
 715   (Lisp_Object string)
 716 {
 717   char *buf;
 718   bool changed = 0;
 719   unsigned char *strp;
 720   char *bufp;
 721   ptrdiff_t idx;
 722   ptrdiff_t bsize;
 723   Lisp_Object tem;
 724   Lisp_Object keymap;
 725   unsigned char *start;
 726   ptrdiff_t length, length_byte;
 727   Lisp_Object name;
 728   struct gcpro gcpro1, gcpro2, gcpro3, gcpro4;
 729   bool multibyte;
 730   ptrdiff_t nchars;
 731
 732   if (NILP (string))
 733     return Qnil;
 734
 735   CHECK_STRING (string);
 736   tem = Qnil;
 737   keymap = Qnil;
 738   name = Qnil;
 739   GCPRO4 (string, tem, keymap, name);
 740
 741   multibyte = STRING_MULTIBYTE (string);
 742   nchars = 0;
 743
 744   /* KEYMAP is either nil (which means search all the active keymaps)
 745      or a specified local map (which means search just that and the
 746      global map).  If non-nil, it might come from Voverriding_local_map,
 747      or from a \\<mapname> construct in STRING itself..  */
 748   keymap = Voverriding_local_map;
 749
 750   bsize = SBYTES (string);
 751   bufp = buf = xmalloc (bsize);
 752
 753   strp = SDATA (string);
 754   while (strp < SDATA (string) + SBYTES (string))
 755     {
 756       if (strp[0] == '\\' && strp[1] == '=')
 757         {
 758           /* \= quotes the next character;
 759              thus, to put in \[ without its special meaning, use \=\[.  */
 760           changed = 1;
 761           strp += 2;
 762           if (multibyte)
 763             {
 764               int len;
 765
 766               STRING_CHAR_AND_LENGTH (strp, len);
 767               if (len == 1)
 768                 *bufp = *strp;
 769               else
 770                 memcpy (bufp, strp, len);
 771               strp += len;
 772               bufp += len;
 773               nchars++;
 774             }
 775           else
 776             *bufp++ = *strp++, nchars++;
 777         }
 778       else if (strp[0] == '\\' && strp[1] == '[')
 779         {
 780           ptrdiff_t start_idx;
 781           bool follow_remap = 1;
 782
 783           changed = 1;
 784           strp += 2;            /* skip \[ */
 785           start = strp;
 786           start_idx = start - SDATA (string);
 787
 788           while ((strp - SDATA (string)
 789                   < SBYTES (string))
 790                  && *strp != ']')
 791             strp++;
 792           length_byte = strp - start;
 793
 794           strp++;               /* skip ] */
 795
 796           /* Save STRP in IDX.  */
 797           idx = strp - SDATA (string);
 798           name = Fintern (make_string ((char *) start, length_byte), Qnil);
 799
 800         do_remap:
 801           tem = Fwhere_is_internal (name, keymap, Qt, Qnil, Qnil);
 802
 803           if (VECTORP (tem) && ASIZE (tem) > 1
 804               && EQ (AREF (tem, 0), Qremap) && SYMBOLP (AREF (tem, 1))
 805               && follow_remap)
 806             {
 807               name = AREF (tem, 1);
 808               follow_remap = 0;
 809               goto do_remap;
 810             }
 811
 812           /* Note the Fwhere_is_internal can GC, so we have to take
 813              relocation of string contents into account.  */
 814           strp = SDATA (string) + idx;
 815           start = SDATA (string) + start_idx;
 816
 817           if (NILP (tem))       /* but not on any keys */
 818             {
 819               ptrdiff_t offset = bufp - buf;
 820               if (STRING_BYTES_BOUND - 4 < bsize)
 821                 string_overflow ();
 822               buf = xrealloc (buf, bsize += 4);
 823               bufp = buf + offset;
 824               memcpy (bufp, "M-x ", 4);
 825               bufp += 4;
 826               nchars += 4;
 827               if (multibyte)
 828                 length = multibyte_chars_in_text (start, length_byte);
 829               else
 830                 length = length_byte;
 831               goto subst;
 832             }
 833           else
 834             {                   /* function is on a key */
 835               tem = Fkey_description (tem, Qnil);
 836               goto subst_string;
 837             }
 838         }
 839       /* \{foo} is replaced with a summary of the keymap (symbol-value foo).
 840          \<foo> just sets the keymap used for \[cmd].  */
 841       else if (strp[0] == '\\' && (strp[1] == '{' || strp[1] == '<'))
 842         {
 843           struct buffer *oldbuf;
 844           ptrdiff_t start_idx;
 845           /* This is for computing the SHADOWS arg for describe_map_tree.  */
 846           Lisp_Object active_maps = Fcurrent_active_maps (Qnil, Qnil);
 847           Lisp_Object earlier_maps;
 848           ptrdiff_t count = SPECPDL_INDEX ();
 849
 850           changed = 1;
 851           strp += 2;            /* skip \{ or \< */
 852           start = strp;
 853           start_idx = start - SDATA (string);
 854
 855           while ((strp - SDATA (string) < SBYTES (string))
 856                  && *strp != '}' && *strp != '>')
 857             strp++;
 858
 859           length_byte = strp - start;
 860           strp++;                       /* skip } or > */
 861
 862           /* Save STRP in IDX.  */
 863           idx = strp - SDATA (string);
 864
 865           /* Get the value of the keymap in TEM, or nil if undefined.
 866              Do this while still in the user's current buffer
 867              in case it is a local variable.  */
 868           name = Fintern (make_string ((char *) start, length_byte), Qnil);
 869           tem = Fboundp (name);
 870           if (! NILP (tem))
 871             {
 872               tem = Fsymbol_value (name);
 873               if (! NILP (tem))
 874                 {
 875                   tem = get_keymap (tem, 0, 1);
 876                   /* Note that get_keymap can GC.  */
 877                   strp = SDATA (string) + idx;
 878                   start = SDATA (string) + start_idx;
 879                 }
 880             }
 881
 882           /* Now switch to a temp buffer.  */
 883           oldbuf = current_buffer;
 884           set_buffer_internal (XBUFFER (Vprin1_to_string_buffer));
 885           /* This is for an unusual case where some after-change
 886              function uses 'format' or 'prin1' or something else that
 887              will thrash Vprin1_to_string_buffer we are using.  */
 888           specbind (Qinhibit_modification_hooks, Qt);
 889
 890           if (NILP (tem))
 891             {
 892               name = Fsymbol_name (name);
 893               insert_string ("\nUses keymap `");
 894               insert_from_string (name, 0, 0,
 895                                   SCHARS (name),
 896                                   SBYTES (name), 1);
 897               insert_string ("', which is not currently defined.\n");
 898               if (start[-1] == '<') keymap = Qnil;
 899             }
 900           else if (start[-1] == '<')
 901             keymap = tem;
 902           else
 903             {
 904               /* Get the list of active keymaps that precede this one.
 905                  If this one's not active, get nil.  */
 906               earlier_maps = Fcdr (Fmemq (tem, Freverse (active_maps)));
 907               describe_map_tree (tem, 1, Fnreverse (earlier_maps),
 908                                  Qnil, 0, 1, 0, 0, 1);
 909             }
 910           tem = Fbuffer_string ();
 911           Ferase_buffer ();
 912           set_buffer_internal (oldbuf);
 913           unbind_to (count, Qnil);
 914
 915         subst_string:
 916           start = SDATA (tem);
 917           length = SCHARS (tem);
 918           length_byte = SBYTES (tem);
 919         subst:
 920           {
 921             ptrdiff_t offset = bufp - buf;
 922             if (STRING_BYTES_BOUND - length_byte < bsize)
 923               string_overflow ();
 924             buf = xrealloc (buf, bsize += length_byte);
 925             bufp = buf + offset;
 926             memcpy (bufp, start, length_byte);
 927             bufp += length_byte;
 928             nchars += length;
 929             /* Check STRING again in case gc relocated it.  */
 930             strp = SDATA (string) + idx;
 931           }
 932         }
 933       else if (! multibyte)             /* just copy other chars */
 934         *bufp++ = *strp++, nchars++;
 935       else
 936         {
 937           int len;
 938
 939           STRING_CHAR_AND_LENGTH (strp, len);
 940           if (len == 1)
 941             *bufp = *strp;
 942           else
 943             memcpy (bufp, strp, len);
 944           strp += len;
 945           bufp += len;
 946           nchars++;
 947         }
 948     }
 949
 950   if (changed)                  /* don't bother if nothing substituted */
 951     tem = make_string_from_bytes (buf, nchars, bufp - buf);
 952   else
 953     tem = string;
 954   xfree (buf);
 955   RETURN_UNGCPRO (tem);
 956 }
 957 \f
 958 void
 959 syms_of_doc (void)
 960 {
 961   DEFSYM (Qfunction_documentation, "function-documentation");
 962
 963   DEFVAR_LISP ("internal-doc-file-name", Vdoc_file_name,
 964                doc: /* Name of file containing documentation strings of built-in symbols.  */);
 965   Vdoc_file_name = Qnil;
 966
 967   DEFVAR_LISP ("build-files", Vbuild_files,
 968                doc: /* A list of files used to build this Emacs binary.  */);
 969   Vbuild_files = Qnil;
 970
 971   defsubr (&Sdocumentation);
 972   defsubr (&Sdocumentation_property);
 973   defsubr (&Ssnarf_documentation);
 974   defsubr (&Ssubstitute_command_keys);
 975 }