ash: [REDIR] Replace GPL noclobberopen code with the FreeBSD version

Upstream commit:

    Date: Thu, 10 Mar 2011 16:52:13 +0800
    [REDIR] Replace GPL noclobberopen code with the FreeBSD version

    Replace noclobberopen() from bash with the FreeBSD code for noclobber
    opens.

    This also reduces code size by eliminating an unnecessary check.

    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

function                                             old     new   delta
changepath                                           192     194      +2
localcmd                                             366     364      -2
expmeta                                              521     517      -4
redirect                                            1210    1135     -75
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/3 up/down: 2/-81)             Total: -79 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash.c

@@ -5174,68 +5174,6 @@ stoppedjobs(void)
 #define EMPTY -2                /* marks an unused slot in redirtab */
 #define CLOSED -3               /* marks a slot of previously-closed fd */
 
-/*
- * Open a file in noclobber mode.
- * The code was copied from bash.
- */
-static int
-noclobberopen(const char *fname)
-{
-	int r, fd;
-	struct stat finfo, finfo2;
-
-	/*
-	 * If the file exists and is a regular file, return an error
-	 * immediately.
-	 */
-	r = stat(fname, &finfo);
-	if (r == 0 && S_ISREG(finfo.st_mode)) {
-		errno = EEXIST;
-		return -1;
-	}
-
-	/*
-	 * If the file was not present (r != 0), make sure we open it
-	 * exclusively so that if it is created before we open it, our open
-	 * will fail.  Make sure that we do not truncate an existing file.
-	 * Note that we don't turn on O_EXCL unless the stat failed -- if the
-	 * file was not a regular file, we leave O_EXCL off.
-	 */
-	if (r != 0)
-		return open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666);
-	fd = open(fname, O_WRONLY|O_CREAT, 0666);
-
-	/* If the open failed, return the file descriptor right away. */
-	if (fd < 0)
-		return fd;
-
-	/*
-	 * OK, the open succeeded, but the file may have been changed from a
-	 * non-regular file to a regular file between the stat and the open.
-	 * We are assuming that the O_EXCL open handles the case where FILENAME
-	 * did not exist and is symlinked to an existing file between the stat
-	 * and open.
-	 */
-
-	/*
-	 * If we can open it and fstat the file descriptor, and neither check
-	 * revealed that it was a regular file, and the file has not been
-	 * replaced, return the file descriptor.
-	 */
-	if (fstat(fd, &finfo2) == 0
-	 && !S_ISREG(finfo2.st_mode)
-	 && finfo.st_dev == finfo2.st_dev
-	 && finfo.st_ino == finfo2.st_ino
-	) {
-		return fd;
-	}
-
-	/* The file has been replaced.  badness. */
-	close(fd);
-	errno = EEXIST;
-	return -1;
-}
-
 /*
  * Handle here documents.  Normally we fork off a process to write the
  * data to a pipe.  If the document is short, we can stuff the data in
@@ -5280,6 +5218,7 @@ openhere(union node *redir)
 static int
 openredirect(union node *redir)
 {
+	struct stat sb;
 	char *fname;
 	int f;
 
@@ -5319,9 +5258,23 @@ openredirect(union node *redir)
 #endif
 		/* Take care of noclobber mode. */
 		if (Cflag) {
-			f = noclobberopen(fname);
+			if (stat(fname, &sb) < 0) {
-			if (f < 0)
+				f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666);
+				if (f < 0)
+					goto ecreate;
+			} else if (!S_ISREG(sb.st_mode)) {
+				f = open(fname, O_WRONLY, 0666);
+				if (f < 0)
+					goto ecreate;
+				if (fstat(f, &sb) < 0 && S_ISREG(sb.st_mode)) {
+					close(f);
+					errno = EEXIST;
+					goto ecreate;
+				}
+			} else {
+				errno = EEXIST;
 				goto ecreate;
+			}
 			break;
 		}
 		/* FALLTHROUGH */