+#ifdef IAMSUID
+static int
+fd_on_nosuid_fs(int fd)
+{
+ int on_nosuid = 0;
+ int check_okay = 0;
+/*
+ * Preferred order: fstatvfs(), fstatfs(), getmntent().
+ * fstatvfs() is UNIX98.
+ * fstatfs() is BSD.
+ * getmntent() is O(number-of-mounted-filesystems) and can hang.
+ */
+
+# ifdef HAS_FSTATVFS
+ struct statvfs stfs;
+ check_okay = fstatvfs(fd, &stfs) == 0;
+ on_nosuid = check_okay && (stfs.f_flag & ST_NOSUID);
+# else
+# if defined(HAS_FSTATFS) && defined(HAS_STRUCT_STATFS_FLAGS)
+ struct statfs stfs;
+ check_okay = fstatfs(fd, &stfs) == 0;
+# undef PERL_MOUNT_NOSUID
+# if !defined(PERL_MOUNT_NOSUID) && defined(MNT_NOSUID)
+# define PERL_MOUNT_NOSUID MNT_NOSUID
+# endif
+# if !defined(PERL_MOUNT_NOSUID) && defined(MS_NOSUID)
+# define PERL_MOUNT_NOSUID MS_NOSUID
+# endif
+# if !defined(PERL_MOUNT_NOSUID) && defined(M_NOSUID)
+# define PERL_MOUNT_NOSUID M_NOSUID
+# endif
+# ifdef PERL_MOUNT_NOSUID
+ on_nosuid = check_okay && (stfs.f_flags & PERL_MOUNT_NOSUID);
+# endif
+# else
+# if defined(HAS_GETMNTENT) && defined(HAS_HASMNTOPT) && defined(MNTOPT_NOSUID)
+ FILE *mtab = fopen("/etc/mtab", "r");
+ struct mntent *entry;
+ struct stat stb, fsb;
+
+ if (mtab && (fstat(fd, &stb) == 0)) {
+ while (entry = getmntent(mtab)) {
+ if (stat(entry->mnt_dir, &fsb) == 0
+ && fsb.st_dev == stb.st_dev)
+ {
+ /* found the filesystem */
+ check_okay = 1;
+ if (hasmntopt(entry, MNTOPT_NOSUID))
+ on_nosuid = 1;
+ break;
+ } /* A single fs may well fail its stat(). */
+ }
+ }
+ if (mtab)
+ fclose(mtab);
+# endif /* mntent */
+# endif /* statfs */
+# endif /* statvfs */
+ if (!check_okay)
+ croak("Can't check filesystem of script \"%s\"", PL_origfilename);
+ return on_nosuid;
+}
+#endif /* IAMSUID */
+