nt/cmdproxy.c

   1 /* Proxy shell designed for use with Emacs on Windows 95 and NT.
   2    Copyright (C) 1997, 2001-2016 Free Software Foundation, Inc.
   3
   4    Accepts subset of Unix sh(1) command-line options, for compatibility
   5    with elisp code written for Unix.  When possible, executes external
   6    programs directly (a common use of /bin/sh by Emacs), otherwise
   7    invokes the user-specified command processor to handle built-in shell
   8    commands, batch files and interactive mode.
   9
  10    The main function is simply to process the "-c string" option in the
  11    way /bin/sh does, since the standard Windows command shells use the
  12    convention that everything after "/c" (the Windows equivalent of
  13    "-c") is the input string.
  14
  15 This file is part of GNU Emacs.
  16
  17 GNU Emacs is free software: you can redistribute it and/or modify
  18 it under the terms of the GNU General Public License as published by
  19 the Free Software Foundation, either version 3 of the License, or (at
  20 your option) any later version.
  21
  22 GNU Emacs is distributed in the hope that it will be useful,
  23 but WITHOUT ANY WARRANTY; without even the implied warranty of
  24 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  25 GNU General Public License for more details.
  26
  27 You should have received a copy of the GNU General Public License
  28 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
  29
  30 #include <windows.h>
  31
  32 #include <stdarg.h>  /* va_args */
  33 #include <malloc.h>  /* alloca */
  34 #include <stdlib.h>  /* getenv */
  35 #include <string.h>  /* strlen */
  36 #include <ctype.h>   /* isspace, isalpha */
  37
  38 /* We don't want to include stdio.h because we are already duplicating
  39    lots of it here */
  40 extern int _snprintf (char *buffer, size_t count, const char *format, ...);
  41
  42 /*******  Mock C library routines  *********************************/
  43
  44 /* These routines are used primarily to minimize the executable size.  */
  45
  46 #define stdout GetStdHandle (STD_OUTPUT_HANDLE)
  47 #define stderr GetStdHandle (STD_ERROR_HANDLE)
  48
  49 int
  50 vfprintf (HANDLE hnd, const char * msg, va_list args)
  51 {
  52   DWORD bytes_written;
  53   char buf[1024];
  54
  55   wvsprintf (buf, msg, args);
  56   return WriteFile (hnd, buf, strlen (buf), &bytes_written, NULL);
  57 }
  58
  59 int
  60 fprintf (HANDLE hnd, const char * msg, ...)
  61 {
  62   va_list args;
  63   int rc;
  64
  65   va_start (args, msg);
  66   rc = vfprintf (hnd, msg, args);
  67   va_end (args);
  68
  69   return rc;
  70 }
  71
  72 int
  73 printf (const char * msg, ...)
  74 {
  75   va_list args;
  76   int rc;
  77
  78   va_start (args, msg);
  79   rc = vfprintf (stdout, msg, args);
  80   va_end (args);
  81
  82   return rc;
  83 }
  84
  85 void
  86 fail (const char * msg, ...)
  87 {
  88   va_list args;
  89
  90   va_start (args, msg);
  91   vfprintf (stderr, msg, args);
  92   va_end (args);
  93
  94   exit (-1);
  95 }
  96
  97 void
  98 warn (const char * msg, ...)
  99 {
 100   va_list args;
 101
 102   va_start (args, msg);
 103   vfprintf (stderr, msg, args);
 104   va_end (args);
 105 }
 106
 107 /******************************************************************/
 108
 109 char *
 110 canon_filename (char *fname)
 111 {
 112   char *p = fname;
 113
 114   while (*p)
 115     {
 116       if (*p == '/')
 117         *p = '\\';
 118       p++;
 119     }
 120
 121   return fname;
 122 }
 123
 124 const char *
 125 skip_space (const char *str)
 126 {
 127   while (isspace (*str)) str++;
 128   return str;
 129 }
 130
 131 const char *
 132 skip_nonspace (const char *str)
 133 {
 134   while (*str && !isspace (*str)) str++;
 135   return str;
 136 }
 137
 138 /* This value is never changed by the code.  We keep the code that
 139    supports also the value of '"', but let's allow the compiler to
 140    optimize it out, until someone actually uses that.  */
 141 const int escape_char = '\\';
 142
 143 /* Get next token from input, advancing pointer.  */
 144 int
 145 get_next_token (char * buf, const char ** pSrc)
 146 {
 147   const char * p = *pSrc;
 148   char * o = buf;
 149
 150   p = skip_space (p);
 151   if (*p == '"')
 152     {
 153       int escape_char_run = 0;
 154
 155       /* Go through src until an ending quote is found, unescaping
 156          quotes along the way.  If the escape char is not quote, then do
 157          special handling of multiple escape chars preceding a quote
 158          char (ie. the reverse of what Emacs does to escape quotes).  */
 159       p++;
 160       while (1)
 161         {
 162           if (p[0] == escape_char && escape_char != '"')
 163             {
 164               escape_char_run++;
 165               p++;
 166               continue;
 167             }
 168           else if (p[0] == '"')
 169             {
 170               while (escape_char_run > 1)
 171                 {
 172                   *o++ = escape_char;
 173                   escape_char_run -= 2;
 174                 }
 175
 176               if (escape_char_run > 0)
 177                 {
 178                   /* escaped quote */
 179                   *o++ = *p++;
 180                   escape_char_run = 0;
 181                 }
 182               else if (p[1] == escape_char && escape_char == '"')
 183                 {
 184                   /* quote escaped by doubling */
 185                   *o++ = *p;
 186                   p += 2;
 187                 }
 188               else
 189                 {
 190                   /* The ending quote.  */
 191                   *o = '\0';
 192                   /* Leave input pointer after token.  */
 193                   p++;
 194                   break;
 195                 }
 196             }
 197           else if (p[0] == '\0')
 198             {
 199               /* End of string, but no ending quote found.  We might want to
 200                  flag this as an error, but for now will consider the end as
 201                  the end of the token.  */
 202               if (escape_char == '\\')
 203                 {
 204                   /* Output literal backslashes.  Note that if the
 205                      token ends with an unpaired backslash, we eat it
 206                      up here.  But since this case invokes undefined
 207                      behavior anyway, it's okay.  */
 208                   while (escape_char_run > 1)
 209                     {
 210                       *o++ = escape_char;
 211                       escape_char_run -= 2;
 212                     }
 213                 }
 214               *o = '\0';
 215               break;
 216             }
 217           else
 218             {
 219               if (escape_char == '\\')
 220                 {
 221                   /* Output literal backslashes.  Note that we don't
 222                      treat a backslash as an escape character here,
 223                      since it doesn't precede a quote.  */
 224                   for ( ; escape_char_run > 0; escape_char_run--)
 225                     *o++ = escape_char;
 226                 }
 227               *o++ = *p++;
 228             }
 229         }
 230     }
 231   else
 232     {
 233       /* Next token is delimited by whitespace.  */
 234       const char * p1 = skip_nonspace (p);
 235       memcpy (o, p, p1 - p);
 236       o += (p1 - p);
 237       *o = '\0';
 238       p = p1;
 239     }
 240
 241   *pSrc = p;
 242
 243   return o - buf;
 244 }
 245
 246 /* Return TRUE if PROGNAME is a batch file. */
 247 BOOL
 248 batch_file_p (const char *progname)
 249 {
 250   const char *exts[] = {".bat", ".cmd"};
 251   int n_exts = sizeof (exts) / sizeof (char *);
 252   int i;
 253
 254   const char *ext = strrchr (progname, '.');
 255
 256   if (ext)
 257     {
 258       for (i = 0; i < n_exts; i++)
 259         {
 260           if (stricmp (ext, exts[i]) == 0)
 261             return TRUE;
 262         }
 263     }
 264
 265   return FALSE;
 266 }
 267
 268 /* Search for EXEC file in DIR.  If EXEC does not have an extension,
 269    DIR is searched for EXEC with the standard extensions appended.  */
 270 int
 271 search_dir (const char *dir, const char *exec, int bufsize, char *buffer)
 272 {
 273   const char *exts[] = {".bat", ".cmd", ".exe", ".com"};
 274   int n_exts = sizeof (exts) / sizeof (char *);
 275   char *dummy;
 276   int i, rc;
 277   const char *pext = strrchr (exec, '\\');
 278
 279   /* Does EXEC already include an extension?  */
 280   if (!pext)
 281     pext = exec;
 282   pext = strchr (pext, '.');
 283
 284   /* Search the directory for the program.  */
 285   if (pext)
 286     {
 287       /* SearchPath will not append an extension if the file already
 288          has an extension, so we must append it ourselves.  */
 289       char exec_ext[MAX_PATH], *p;
 290
 291       p = strcpy (exec_ext, exec) + strlen (exec);
 292
 293       /* Search first without any extension; if found, we are done.  */
 294       rc = SearchPath (dir, exec_ext, NULL, bufsize, buffer, &dummy);
 295       if (rc > 0)
 296         return rc;
 297
 298       /* Try the known extensions.  */
 299       for (i = 0; i < n_exts; i++)
 300         {
 301           strcpy (p, exts[i]);
 302           rc = SearchPath (dir, exec_ext, NULL, bufsize, buffer, &dummy);
 303           if (rc > 0)
 304             return rc;
 305         }
 306     }
 307   else
 308     {
 309       for (i = 0; i < n_exts; i++)
 310         {
 311           rc = SearchPath (dir, exec, exts[i], bufsize, buffer, &dummy);
 312           if (rc > 0)
 313             return rc;
 314         }
 315     }
 316
 317   return 0;
 318 }
 319
 320 /* Return the absolute name of executable file PROG, including
 321    any file extensions.  If an absolute name for PROG cannot be found,
 322    return NULL.  */
 323 char *
 324 make_absolute (const char *prog)
 325 {
 326   char absname[MAX_PATH];
 327   char dir[MAX_PATH];
 328   char curdir[MAX_PATH];
 329   char *p, *path;
 330   const char *fname;
 331
 332   /* At least partial absolute path specified; search there.  */
 333   if ((isalpha (prog[0]) && prog[1] == ':') ||
 334       (prog[0] == '\\'))
 335     {
 336       /* Split the directory from the filename.  */
 337       fname = strrchr (prog, '\\');
 338       if (!fname)
 339         /* Only a drive specifier is given.  */
 340         fname = prog + 2;
 341       strncpy (dir, prog, fname - prog);
 342       dir[fname - prog] = '\0';
 343
 344       /* Search the directory for the program.  */
 345       if (search_dir (dir, prog, MAX_PATH, absname) > 0)
 346         return strdup (absname);
 347       else
 348         return NULL;
 349     }
 350
 351   if (GetCurrentDirectory (MAX_PATH, curdir) <= 0)
 352     return NULL;
 353
 354   /* Relative path; search in current dir. */
 355   if (strpbrk (prog, "\\"))
 356     {
 357       if (search_dir (curdir, prog, MAX_PATH, absname) > 0)
 358         return strdup (absname);
 359       else
 360         return NULL;
 361     }
 362
 363   /* Just filename; search current directory then PATH.  */
 364   path = alloca (strlen (getenv ("PATH")) + strlen (curdir) + 2);
 365   strcpy (path, curdir);
 366   strcat (path, ";");
 367   strcat (path, getenv ("PATH"));
 368
 369   while (*path)
 370     {
 371       size_t len;
 372
 373       /* Get next directory from path.  */
 374       p = path;
 375       while (*p && *p != ';') p++;
 376       /* A broken PATH could have too long directory names in it.  */
 377       len = min (p - path, sizeof (dir) - 1);
 378       strncpy (dir, path, len);
 379       dir[len] = '\0';
 380
 381       /* Search the directory for the program.  */
 382       if (search_dir (dir, prog, MAX_PATH, absname) > 0)
 383         return strdup (absname);
 384
 385       /* Move to the next directory.  */
 386       path = p + 1;
 387     }
 388
 389   return NULL;
 390 }
 391
 392 /* Try to decode the given command line the way cmd would do it.  On
 393    success, return 1 with cmdline dequoted.  Otherwise, when we've
 394    found constructs only cmd can properly interpret, return 0 and
 395    leave cmdline unchanged.  */
 396 int
 397 try_dequote_cmdline (char* cmdline)
 398 {
 399   /* Dequoting can only subtract characters, so the length of the
 400      original command line is a bound on the amount of scratch space
 401      we need.  This length, in turn, is bounded by the 32k
 402      CreateProcess limit.  */
 403   char * old_pos = cmdline;
 404   char * new_cmdline = alloca (strlen(cmdline));
 405   char * new_pos = new_cmdline;
 406   char c;
 407
 408   enum {
 409     NORMAL,
 410     AFTER_CARET,
 411     INSIDE_QUOTE
 412   } state = NORMAL;
 413
 414   while ((c = *old_pos++))
 415     {
 416       switch (state)
 417         {
 418         case NORMAL:
 419           switch(c)
 420             {
 421             case '"':
 422               *new_pos++ = c;
 423               state = INSIDE_QUOTE;
 424               break;
 425             case '^':
 426               state = AFTER_CARET;
 427               break;
 428             case '<': case '>':
 429             case '&': case '|':
 430             case '(': case ')':
 431             case '%': case '!':
 432               /* We saw an unquoted shell metacharacter and we don't
 433                  understand it. Bail out.  */
 434               return 0;
 435             default:
 436               *new_pos++ = c;
 437               break;
 438             }
 439           break;
 440         case AFTER_CARET:
 441           *new_pos++ = c;
 442           state = NORMAL;
 443           break;
 444         case INSIDE_QUOTE:
 445           switch (c)
 446             {
 447             case '"':
 448               *new_pos++ = c;
 449               state = NORMAL;
 450               break;
 451             case '%':
 452             case '!':
 453               /* Variable substitution inside quote.  Bail out.  */
 454               return 0;
 455             default:
 456               *new_pos++ = c;
 457               break;
 458             }
 459           break;
 460         }
 461     }
 462
 463   /* We were able to dequote the entire string.  Copy our scratch
 464      buffer on top of the original buffer and return success.  */
 465   memcpy (cmdline, new_cmdline, new_pos - new_cmdline);
 466   cmdline[new_pos - new_cmdline] = '\0';
 467   return 1;
 468 }
 469
 470 /*****************************************************************/
 471
 472 #if 0
 473 char ** _argv;
 474 int     _argc;
 475
 476 /* Parse commandline into argv array, allowing proper quoting of args.  */
 477 void
 478 setup_argv (void)
 479 {
 480   char * cmdline = GetCommandLine ();
 481   int arg_bytes = 0;
 482
 483
 484 }
 485 #endif
 486
 487 /* Information about child proc is global, to allow for automatic
 488    termination when interrupted.  At the moment, only one child process
 489    can be running at any one time.  */
 490
 491 PROCESS_INFORMATION child;
 492 int interactive = TRUE;
 493
 494 BOOL
 495 console_event_handler (DWORD event)
 496 {
 497   switch (event)
 498     {
 499     case CTRL_C_EVENT:
 500     case CTRL_BREAK_EVENT:
 501       if (!interactive)
 502         {
 503           /* Both command.com and cmd.exe have the annoying behavior of
 504              prompting "Terminate batch job (y/n)?" when interrupted
 505              while running a batch file, even if running in
 506              non-interactive (-c) mode.  Try to make up for this
 507              deficiency by forcibly terminating the subprocess if
 508              running non-interactively.  */
 509           if (child.hProcess &&
 510               WaitForSingleObject (child.hProcess, 500) != WAIT_OBJECT_0)
 511             TerminateProcess (child.hProcess, 0);
 512           exit (STATUS_CONTROL_C_EXIT);
 513         }
 514       break;
 515
 516 #if 0
 517     default:
 518       /* CLOSE, LOGOFF and SHUTDOWN events - actually we don't get these
 519          under Windows 95.  */
 520       fail ("cmdproxy: received %d event\n", event);
 521       if (child.hProcess)
 522         TerminateProcess (child.hProcess, 0);
 523 #endif
 524     }
 525   return TRUE;
 526 }
 527
 528 /* Change from normal usage; return value indicates whether spawn
 529    succeeded or failed - program return code is returned separately.  */
 530 int
 531 spawn (const char *progname, char *cmdline, const char *dir, int *retcode)
 532 {
 533   BOOL success = FALSE;
 534   SECURITY_ATTRIBUTES sec_attrs;
 535   STARTUPINFO start;
 536   /* In theory, passing NULL for the environment block to CreateProcess
 537      is the same as passing the value of GetEnvironmentStrings, but
 538      doing this explicitly seems to cure problems running DOS programs
 539      in some cases.  */
 540   char * envblock = GetEnvironmentStrings ();
 541
 542   sec_attrs.nLength = sizeof (sec_attrs);
 543   sec_attrs.lpSecurityDescriptor = NULL;
 544   sec_attrs.bInheritHandle = FALSE;
 545
 546   memset (&start, 0, sizeof (start));
 547   start.cb = sizeof (start);
 548
 549   /* CreateProcess handles batch files as progname specially. This
 550      special handling fails when both the batch file and arguments are
 551      quoted.  We pass NULL as progname to avoid the special
 552      handling. */
 553   if (progname != NULL && cmdline[0] == '"' && batch_file_p (progname))
 554       progname = NULL;
 555
 556   if (CreateProcess (progname, cmdline, &sec_attrs, NULL, TRUE,
 557                      0, envblock, dir, &start, &child))
 558   {
 559     success = TRUE;
 560     /* wait for completion and pass on return code */
 561     WaitForSingleObject (child.hProcess, INFINITE);
 562     if (retcode)
 563       GetExitCodeProcess (child.hProcess, (DWORD *)retcode);
 564     CloseHandle (child.hThread);
 565     CloseHandle (child.hProcess);
 566     child.hProcess = NULL;
 567   }
 568
 569   FreeEnvironmentStrings (envblock);
 570
 571   return success;
 572 }
 573
 574 /* Return size of current environment block.  */
 575 int
 576 get_env_size (void)
 577 {
 578   char * start = GetEnvironmentStrings ();
 579   char * tmp = start;
 580
 581   while (tmp[0] || tmp[1])
 582     ++tmp;
 583   FreeEnvironmentStrings (start);
 584   return  tmp + 2 - start;
 585 }
 586
 587 /*******  Main program  ********************************************/
 588
 589 int
 590 main (int argc, char ** argv)
 591 {
 592   int rc;
 593   int need_shell;
 594   char * cmdline;
 595   char * progname;
 596   int envsize;
 597   char **pass_through_args;
 598   int num_pass_through_args;
 599   char modname[MAX_PATH];
 600   char path[MAX_PATH];
 601   char dir[MAX_PATH];
 602   int status;
 603
 604   interactive = TRUE;
 605
 606   SetConsoleCtrlHandler ((PHANDLER_ROUTINE) console_event_handler, TRUE);
 607
 608   if (!GetCurrentDirectory (sizeof (dir), dir))
 609     fail ("error: GetCurrentDirectory failed\n");
 610
 611   /* We serve double duty: we can be called either as a proxy for the
 612      real shell (that is, because we are defined to be the user shell),
 613      or in our role as a helper application for running DOS programs.
 614      In the former case, we interpret the command line options as if we
 615      were a Unix shell, but in the latter case we simply pass our
 616      command line to CreateProcess.  We know which case we are dealing
 617      with by whether argv[0] refers to ourself or to some other program.
 618      (This relies on an arcane feature of CreateProcess, where we can
 619      specify cmdproxy as the module to run, but specify a different
 620      program in the command line - the MSVC startup code sets argv[0]
 621      from the command line.)  */
 622
 623   if (!GetModuleFileName (NULL, modname, sizeof (modname)))
 624     fail ("error: GetModuleFileName failed\n");
 625
 626   /* Change directory to location of .exe so startup directory can be
 627      deleted.  */
 628   progname = strrchr (modname, '\\');
 629   *progname = '\0';
 630   SetCurrentDirectory (modname);
 631   *progname = '\\';
 632
 633   /* Due to problems with interaction between API functions that use "OEM"
 634      codepage vs API functions that use the "ANSI" codepage, we need to
 635      make things consistent by choosing one and sticking with it.  */
 636   SetConsoleCP (GetACP ());
 637   SetConsoleOutputCP (GetACP ());
 638
 639   /* Although Emacs always sets argv[0] to an absolute pathname, we
 640      might get run in other ways as well, so convert argv[0] to an
 641      absolute name before comparing to the module name.  */
 642   path[0] = '\0';
 643   /* The call to SearchPath will find argv[0] in the current
 644      directory, append ".exe" to it if needed, and also canonicalize
 645      it, to resolve references to ".", "..", etc.  */
 646   status = SearchPath (NULL, argv[0], ".exe", sizeof (path), path,
 647                                   &progname);
 648   if (!(status > 0 && stricmp (modname, path) == 0))
 649     {
 650       if (status <= 0)
 651         {
 652           char *s;
 653
 654           /* Make sure we have argv[0] in path[], as the failed
 655              SearchPath might not have copied it there.  */
 656           strcpy (path, argv[0]);
 657           /* argv[0] could include forward slashes; convert them all
 658              to backslashes, for strrchr calls below to DTRT.  */
 659           for (s = path; *s; s++)
 660             if (*s == '/')
 661               *s = '\\';
 662         }
 663       /* Perhaps MODNAME and PATH use mixed short and long file names.  */
 664       if (!(GetShortPathName (modname, modname, sizeof (modname))
 665             && GetShortPathName (path, path, sizeof (path))
 666             && stricmp (modname, path) == 0))
 667         {
 668           /* Sometimes GetShortPathName fails because one or more
 669              directories leading to argv[0] have issues with access
 670              rights.  In that case, at least we can compare the
 671              basenames.  Note: this disregards the improbable case of
 672              invoking a program of the same name from another
 673              directory, since the chances of that other executable to
 674              be both our namesake and a 16-bit DOS application are nil.  */
 675           char *p = strrchr (path, '\\');
 676           char *q = strrchr (modname, '\\');
 677           char *pdot, *qdot;
 678
 679           if (!p)
 680             p = strchr (path, ':');
 681           if (!p)
 682             p = path;
 683           else
 684             p++;
 685           if (!q)
 686             q = strchr (modname, ':');
 687           if (!q)
 688             q = modname;
 689           else
 690             q++;
 691
 692           pdot = strrchr (p, '.');
 693           if (!pdot || stricmp (pdot, ".exe") != 0)
 694             pdot = p + strlen (p);
 695           qdot = strrchr (q, '.');
 696           if (!qdot || stricmp (qdot, ".exe") != 0)
 697             qdot = q + strlen (q);
 698           if (pdot - p != qdot - q || strnicmp (p, q, pdot - p) != 0)
 699             {
 700               /* We are being used as a helper to run a DOS app; just
 701                  pass command line to DOS app without change.  */
 702               /* TODO: fill in progname.  */
 703               if (spawn (NULL, GetCommandLine (), dir, &rc))
 704                 return rc;
 705               fail ("Could not run %s\n", GetCommandLine ());
 706             }
 707         }
 708     }
 709
 710   /* Process command line.  If running interactively (-c or /c not
 711      specified) then spawn a real command shell, passing it the command
 712      line arguments.
 713
 714      If not running interactively, then attempt to execute the specified
 715      command directly.  If necessary, spawn a real shell to execute the
 716      command.
 717
 718   */
 719
 720   progname = NULL;
 721   cmdline = NULL;
 722   /* If no args, spawn real shell for interactive use.  */
 723   need_shell = TRUE;
 724   interactive = TRUE;
 725   /* Ask command.com to create an environment block with a reasonable
 726      amount of free space.  */
 727   envsize = get_env_size () + 300;
 728   pass_through_args = (char **) alloca (argc * sizeof (char *));
 729   num_pass_through_args = 0;
 730
 731   while (--argc > 0)
 732     {
 733       ++argv;
 734       /* Act on switches we recognize (mostly single letter switches,
 735          except for -e); all unrecognized switches and extra args are
 736          passed on to real shell if used (only really of benefit for
 737          interactive use, but allow for batch use as well).  Accept / as
 738          switch char for compatibility with cmd.exe.  */
 739       if (((*argv)[0] == '-' || (*argv)[0] == '/') && (*argv)[1] != '\0')
 740         {
 741           if (((*argv)[1] == 'c' || (*argv)[1] == 'C') && ((*argv)[2] == '\0'))
 742             {
 743               if (--argc == 0)
 744                 fail ("error: expecting arg for %s\n", *argv);
 745               cmdline = *(++argv);
 746               interactive = FALSE;
 747             }
 748           else if (((*argv)[1] == 'i' || (*argv)[1] == 'I') && ((*argv)[2] == '\0'))
 749             {
 750               if (cmdline)
 751                 warn ("warning: %s ignored because of -c\n", *argv);
 752             }
 753           else if (((*argv)[1] == 'e' || (*argv)[1] == 'E') && ((*argv)[2] == ':'))
 754             {
 755               int requested_envsize = atoi (*argv + 3);
 756               /* Enforce a reasonable minimum size, as above.  */
 757               if (requested_envsize > envsize)
 758                 envsize = requested_envsize;
 759               /* For sanity, enforce a reasonable maximum.  */
 760               if (envsize > 32768)
 761                 envsize = 32768;
 762             }
 763           else
 764             {
 765               /* warn ("warning: unknown option %s ignored", *argv); */
 766               pass_through_args[num_pass_through_args++] = *argv;
 767             }
 768         }
 769       else
 770         break;
 771     }
 772
 773 #if 0
 774   /* I think this is probably not useful - cmd.exe ignores extra
 775      (non-switch) args in interactive mode, and they cannot be passed on
 776      when -c was given.  */
 777
 778   /* Collect any remaining args after (initial) switches.  */
 779   while (argc-- > 0)
 780     {
 781       pass_through_args[num_pass_through_args++] = *argv++;
 782     }
 783 #else
 784   /* Probably a mistake for there to be extra args; not fatal.  */
 785   if (argc > 0)
 786     warn ("warning: extra args ignored after '%s'\n", argv[-1]);
 787 #endif
 788
 789   pass_through_args[num_pass_through_args] = NULL;
 790
 791   /* If -c option, determine if we must spawn a real shell, or if we can
 792      execute the command directly ourself.  */
 793   if (cmdline)
 794     {
 795       const char *args;
 796
 797       /* The program name is the first token of cmdline.  Since
 798          filenames cannot legally contain embedded quotes, the value
 799          of escape_char doesn't matter.  */
 800       args = cmdline;
 801       if (!get_next_token (path, &args))
 802         fail ("error: no program name specified.\n");
 803
 804       canon_filename (path);
 805       progname = make_absolute (path);
 806
 807       /* If we found the program and the rest of the command line does
 808          not contain unquoted shell metacharacters, run the program
 809          directly (if not found it might be an internal shell command,
 810          so don't fail).  */
 811       if (progname != NULL && try_dequote_cmdline (cmdline))
 812         need_shell = FALSE;
 813       else
 814         progname = NULL;
 815     }
 816
 817  pass_to_shell:
 818   if (need_shell)
 819     {
 820       char * p;
 821       int    extra_arg_space = 0;
 822       int    maxlen, remlen;
 823       int    run_command_dot_com;
 824
 825       progname = getenv ("COMSPEC");
 826       if (!progname)
 827         fail ("error: COMSPEC is not set\n");
 828
 829       canon_filename (progname);
 830       progname = make_absolute (progname);
 831
 832       if (progname == NULL || strchr (progname, '\\') == NULL)
 833         fail ("error: the program %s could not be found.\n", getenv ("COMSPEC"));
 834
 835       /* Need to set environment size when running command.com.  */
 836       run_command_dot_com =
 837         (stricmp (strrchr (progname, '\\'), "command.com") == 0);
 838
 839       /* Work out how much extra space is required for
 840          pass_through_args.  */
 841       for (argv = pass_through_args; *argv != NULL; ++argv)
 842         /* We don't expect to have to quote switches.  */
 843         extra_arg_space += strlen (*argv) + 2;
 844
 845       if (cmdline)
 846         {
 847           char * buf;
 848
 849           /* Convert to syntax expected by cmd.exe/command.com for
 850              running non-interactively.  Always quote program name in
 851              case path contains spaces (fortunately it can't contain
 852              quotes, since they are illegal in path names).  */
 853
 854           remlen = maxlen =
 855             strlen (progname) + extra_arg_space + strlen (cmdline) + 16 + 2;
 856           buf = p = alloca (maxlen + 1);
 857
 858           /* Quote progname in case it contains spaces.  */
 859           p += _snprintf (p, remlen, "\"%s\"", progname);
 860           remlen = maxlen - (p - buf);
 861
 862           /* Include pass_through_args verbatim; these are just switches
 863              so should not need quoting.  */
 864           for (argv = pass_through_args; *argv != NULL; ++argv)
 865             {
 866               p += _snprintf (p, remlen, " %s", *argv);
 867               remlen = maxlen - (p - buf);
 868             }
 869
 870           /* Now that we know we will be invoking the shell, quote the
 871              command line after the "/c" switch as the shell expects:
 872              a single pair of quotes enclosing the entire command
 873              tail, no matter whether quotes are used in the command
 874              line, and how many of them are there.  See the output of
 875              "cmd /?" for how cmd.exe treats quotes.  */
 876           if (run_command_dot_com)
 877             _snprintf (p, remlen, " /e:%d /c \"%s\"", envsize, cmdline);
 878           else
 879             _snprintf (p, remlen, " /c \"%s\"", cmdline);
 880           cmdline = buf;
 881         }
 882       else
 883         {
 884           if (run_command_dot_com)
 885             {
 886               /* Provide dir arg expected by command.com when first
 887                  started interactively (the "command search path").  To
 888                  avoid potential problems with spaces in command dir
 889                  (which cannot be quoted - command.com doesn't like it),
 890                  we always use the 8.3 form.  */
 891               GetShortPathName (progname, path, sizeof (path));
 892               p = strrchr (path, '\\');
 893               /* Trailing slash is acceptable, so always leave it.  */
 894               *(++p) = '\0';
 895             }
 896           else
 897             path[0] = '\0';
 898
 899           remlen = maxlen =
 900             strlen (progname) + extra_arg_space + strlen (path) + 13;
 901           cmdline = p = alloca (maxlen + 1);
 902
 903           /* Quote progname in case it contains spaces.  */
 904           p += _snprintf (p, remlen, "\"%s\" %s", progname, path);
 905           remlen = maxlen - (p - cmdline);
 906
 907           /* Include pass_through_args verbatim; these are just switches
 908              so should not need quoting.  */
 909           for (argv = pass_through_args; *argv != NULL; ++argv)
 910             {
 911               p += _snprintf (p, remlen, " %s", *argv);
 912               remlen = maxlen - (p - cmdline);
 913             }
 914
 915           if (run_command_dot_com)
 916             _snprintf (p, remlen, " /e:%d", envsize);
 917         }
 918     }
 919
 920   if (!progname)
 921     fail ("Internal error: program name not defined\n");
 922
 923   if (!cmdline)
 924     cmdline = progname;
 925
 926   if (spawn (progname, cmdline, dir, &rc))
 927     return rc;
 928
 929   if (!need_shell)
 930     {
 931       need_shell = TRUE;
 932       goto pass_to_shell;
 933     }
 934
 935   fail ("Could not run %s\n", progname);
 936
 937   return 0;
 938 }