gnulib/lib/w32spawn.h

/* Auxiliary functions for the creation of subprocesses.  Native Woe32 API.
   Copyright (C) 2003, 2006, 2007 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2003.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/* Get declarations of the Win32 API functions.  */
#define WIN32_LEAN_AND_MEAN
#include <windows.h>

/* Get _get_osfhandle() and _open_osfhandle().  */
#include <io.h>

#include <stdbool.h>
#include <string.h>
#include <errno.h>

#include "xalloc.h"

/* Duplicates a file handle, making the copy uninheritable.  */
static int
dup_noinherit (int fd)
{
  HANDLE curr_process = GetCurrentProcess ();
  HANDLE old_handle = (HANDLE) _get_osfhandle (fd);
  HANDLE new_handle;
  int nfd;

  if (!DuplicateHandle (curr_process,		    /* SourceProcessHandle */
			old_handle,		    /* SourceHandle */
			curr_process,		    /* TargetProcessHandle */
			(PHANDLE) &new_handle,	    /* TargetHandle */
			(DWORD) 0,		    /* DesiredAccess */
			FALSE,			    /* InheritHandle */
			DUPLICATE_SAME_ACCESS))	    /* Options */
    error (EXIT_FAILURE, 0, _("DuplicateHandle failed with error code 0x%08x"),
	   GetLastError ());

  nfd = _open_osfhandle ((long) new_handle, O_BINARY);
  if (nfd < 0)
    error (EXIT_FAILURE, errno, _("_open_osfhandle failed"));

  return nfd;
}

/* Prepares an argument vector before calling spawn().
   Note that spawn() does not by itself call the command interpreter
     (getenv ("COMSPEC") != NULL ? getenv ("COMSPEC") :
      ({ OSVERSIONINFO v; v.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
         GetVersionEx(&v);
         v.dwPlatformId == VER_PLATFORM_WIN32_NT;
      }) ? "cmd.exe" : "command.com").
   Instead it simply concatenates the arguments, separated by ' ', and calls
   CreateProcess().  We must quote the arguments since Win32 CreateProcess()
   interprets characters like ' ', '\t', '\\', '"' (but not '<' and '>') in a
   special way:
   - Space and tab are interpreted as delimiters. They are not treated as
     delimiters if they are surrounded by double quotes: "...".
   - Unescaped double quotes are removed from the input. Their only effect is
     that within double quotes, space and tab are treated like normal
     characters.
   - Backslashes not followed by double quotes are not special.
   - But 2*n+1 backslashes followed by a double quote become
     n backslashes followed by a double quote (n >= 0):
       \" -> "
       \\\" -> \"
       \\\\\" -> \\"
 */
#define SHELL_SPECIAL_CHARS "\"\\ \001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037"
#define SHELL_SPACE_CHARS " \001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037"
static char **
prepare_spawn (char **argv)
{
  size_t argc;
  char **new_argv;
  size_t i;

  /* Count number of arguments.  */
  for (argc = 0; argv[argc] != NULL; argc++)
    ;

  /* Allocate new argument vector.  */
  new_argv = XNMALLOC (argc + 1, char *);

  /* Put quoted arguments into the new argument vector.  */
  for (i = 0; i < argc; i++)
    {
      const char *string = argv[i];

      if (string[0] == '\0')
	new_argv[i] = xstrdup ("\"\"");
      else if (strpbrk (string, SHELL_SPECIAL_CHARS) != NULL)
	{
	  bool quote_around = (strpbrk (string, SHELL_SPACE_CHARS) != NULL);
	  size_t length;
	  unsigned int backslashes;
	  const char *s;
	  char *quoted_string;
	  char *p;

	  length = 0;
	  backslashes = 0;
	  if (quote_around)
	    length++;
	  for (s = string; *s != '\0'; s++)
	    {
	      char c = *s;
	      if (c == '"')
		length += backslashes + 1;
	      length++;
	      if (c == '\\')
		backslashes++;
	      else
		backslashes = 0;
	    }
	  if (quote_around)
	    length += backslashes + 1;

	  quoted_string = (char *) xmalloc (length + 1);

	  p = quoted_string;
	  backslashes = 0;
	  if (quote_around)
	    *p++ = '"';
	  for (s = string; *s != '\0'; s++)
	    {
	      char c = *s;
	      if (c == '"')
		{
		  unsigned int j;
		  for (j = backslashes + 1; j > 0; j--)
		    *p++ = '\\';
		}
	      *p++ = c;
	      if (c == '\\')
		backslashes++;
	      else
		backslashes = 0;
	    }
	  if (quote_around)
	    {
	      unsigned int j;
	      for (j = backslashes; j > 0; j--)
		*p++ = '\\';
	      *p++ = '"';
	    }
	  *p = '\0';

	  new_argv[i] = quoted_string;
	}
      else
	new_argv[i] = (char *) string;
    }
  new_argv[argc] = NULL;

  return new_argv;
}