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diff --git a/lib/w32spawn.h b/lib/w32spawn.h
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+/* Auxiliary functions for the creation of subprocesses. Native Woe32 API.
+ Copyright (C) 2001, 2003-2011 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 3 of the License, 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, see <http://www.gnu.org/licenses/>. */
+
+/* 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 <unistd.h>
+#include <errno.h>
+
+#include "cloexec.h"
+#include "xalloc.h"
+
+/* Duplicates a file handle, making the copy uninheritable.
+ Returns -1 for a file handle that is equivalent to closed. */
+static int
+dup_noinherit (int fd)
+{
+ fd = dup_cloexec (fd);
+ if (fd < 0 && errno == EMFILE)
+ error (EXIT_FAILURE, errno, _("_open_osfhandle failed"));
+
+ return fd;
+}
+
+/* Returns a file descriptor equivalent to FD, except that the resulting file
+ descriptor is none of STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO.
+ FD must be open and non-inheritable. The result will be non-inheritable as
+ well.
+ If FD < 0, FD itself is returned. */
+static int
+fd_safer_noinherit (int fd)
+{
+ if (STDIN_FILENO <= fd && fd <= STDERR_FILENO)
+ {
+ /* The recursion depth is at most 3. */
+ int nfd = fd_safer_noinherit (dup_noinherit (fd));
+ int saved_errno = errno;
+ close (fd);
+ errno = saved_errno;
+ return nfd;
+ }
+ return fd;
+}
+
+/* Duplicates a file handle, making the copy uninheritable and ensuring the
+ result is none of STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO.
+ Returns -1 for a file handle that is equivalent to closed. */
+static int
+dup_safer_noinherit (int fd)
+{
+ return fd_safer_noinherit (dup_noinherit (fd));
+}
+
+/* Undoes the effect of TEMPFD = dup_safer_noinherit (ORIGFD); */
+static void
+undup_safer_noinherit (int tempfd, int origfd)
+{
+ if (tempfd >= 0)
+ {
+ if (dup2 (tempfd, origfd) < 0)
+ error (EXIT_FAILURE, errno, _("cannot restore fd %d: dup2 failed"),
+ origfd);
+ close (tempfd);
+ }
+ else
+ {
+ /* origfd was closed or open to no handle at all. Set it to a closed
+ state. This is (nearly) equivalent to the original state. */
+ close (origfd);
+ }
+}
+
+/* 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 (1 + argc + 1, char *);
+
+ /* Add an element upfront that can be used when argv[0] turns out to be a
+ script, not a program.
+ On Unix, this would be "/bin/sh". On native Windows, "sh" is actually
+ "sh.exe". We have to omit the directory part and rely on the search in
+ PATH, because the mingw "mount points" are not visible inside Win32
+ CreateProcess(). */
+ *new_argv++ = "sh.exe";
+
+ /* 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;
+}