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+/* Create a symlink relative to an open directory.
+ Copyright (C) 2009-2022 Free Software Foundation, Inc.
+
+ 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 <https://www.gnu.org/licenses/>. */
+
+/* written by Eric Blake */
+
+#include <config.h>
+
+/* Specification. */
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdlib.h>
+
+#if HAVE_SYMLINKAT
+# undef symlinkat
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <string.h>
+
+/* Create a symlink, but reject trailing slash. */
+int
+rpl_symlinkat (char const *contents, int fd, char const *name)
+{
+ size_t len = strlen (name);
+ if (len && name[len - 1] == '/')
+ {
+ struct stat st;
+ if (fstatat (fd, name, &st, AT_SYMLINK_NOFOLLOW) == 0
+ || errno == EOVERFLOW)
+ errno = EEXIST;
+ return -1;
+ }
+ return symlinkat (contents, fd, name);
+}
+
+#elif !HAVE_SYMLINK
+/* Mingw lacks symlink, and it is more efficient to provide a trivial
+ wrapper than to go through at-func.c to call rpl_symlink. */
+
+int
+symlinkat (_GL_UNUSED char const *path1, _GL_UNUSED int fd,
+ _GL_UNUSED char const *path2)
+{
+ errno = ENOSYS;
+ return -1;
+}
+
+#else /* HAVE_SYMLINK */
+
+/* Our openat helper functions expect the directory parameter first,
+ not second. These shims make life easier. */
+
+/* Like symlink, but with arguments reversed. */
+static int
+symlink_reversed (char const *file, char const *contents)
+{
+ return symlink (contents, file);
+}
+
+/* Like symlinkat, but with arguments reversed. */
+
+static int
+symlinkat_reversed (int fd, char const *file, char const *contents);
+
+# define AT_FUNC_NAME symlinkat_reversed
+# define AT_FUNC_F1 symlink_reversed
+# define AT_FUNC_POST_FILE_PARAM_DECLS , char const *contents
+# define AT_FUNC_POST_FILE_ARGS , contents
+# include "at-func.c"
+# undef AT_FUNC_NAME
+# undef AT_FUNC_F1
+# undef AT_FUNC_POST_FILE_PARAM_DECLS
+# undef AT_FUNC_POST_FILE_ARGS
+
+/* Create a symlink FILE, in the directory open on descriptor FD,
+ holding CONTENTS. If possible, do it without changing the
+ working directory. Otherwise, resort to using save_cwd/fchdir,
+ then symlink/restore_cwd. If either the save_cwd or the restore_cwd
+ fails, then give a diagnostic and exit nonzero. */
+
+int
+symlinkat (char const *contents, int fd, char const *file)
+{
+ return symlinkat_reversed (fd, file, contents);
+}
+
+#endif /* HAVE_SYMLINK */