--- /dev/null
+for systems that don't support latest POSIX standard: %as
+
+https://bugs.gentoo.org/406303
+
+--- a/configure.ac
++++ b/configure.ac
+@@ -688,7 +688,6 @@ AC_ARG_ENABLE([libmount],
+ UL_BUILD_INIT([libmount])
+ UL_REQUIRES_LINUX([libmount])
+ UL_REQUIRES_BUILD([libmount], [libblkid])
+-UL_REQUIRES_HAVE([libmount], [scanf_alloc_modifier], [scanf string alloc modifier])
+ AM_CONDITIONAL(BUILD_LIBMOUNT, test "x$build_libmount" = xyes)
+
+ AC_SUBST([LIBMOUNT_VERSION])
+--- a/libmount/src/tab_parse.c
++++ b/libmount/src/tab_parse.c
+@@ -22,6 +22,10 @@
+ #include "pathnames.h"
+ #include "strutils.h"
+
++#ifndef HAVE_SCANF_MS_MODIFIER
++# define UL_SCNsA "%s"
++#endif
++
+ static inline char *skip_spaces(char *s)
+ {
+ assert(s);
+@@ -61,16 +65,31 @@ static int mnt_parse_table_line(struct l
+ int rc, n = 0, xrc;
+ char *src = NULL, *fstype = NULL, *optstr = NULL;
+
++#ifndef HAVE_SCANF_MS_MODIFIER
++ size_t len = strlen(s) + 1;
++ src = malloc(len);
++ fstype = malloc(len);
++ fs->target = malloc(len);
++ optstr = malloc(len);
++#endif
++
+ rc = sscanf(s, UL_SCNsA" " /* (1) source */
+ UL_SCNsA" " /* (2) target */
+ UL_SCNsA" " /* (3) FS type */
+ UL_SCNsA" " /* (4) options */
+ "%n", /* byte count */
+
++#ifdef HAVE_SCANF_MS_MODIFIER
+ &src,
+ &fs->target,
+ &fstype,
+ &optstr,
++#else
++ src,
++ fs->target,
++ fstype,
++ optstr,
++#endif
+ &n);
+ xrc = rc;
+
+@@ -136,6 +155,16 @@ static int mnt_parse_mountinfo_line(stru
+ unsigned int maj, min;
+ char *fstype = NULL, *src = NULL, *p;
+
++#ifndef HAVE_SCANF_MS_MODIFIER
++ size_t len = strlen(s) + 1;
++ fs->root = malloc(len);
++ fs->target = malloc(len);
++ fs->vfs_optstr = malloc(len);
++ fs->fs_optstr = malloc(len);
++ fstype = malloc(len);
++ src = malloc(len);
++#endif
++
+ rc = sscanf(s, "%u " /* (1) id */
+ "%u " /* (2) parent */
+ "%u:%u " /* (3) maj:min */
+@@ -147,9 +176,15 @@ static int mnt_parse_mountinfo_line(stru
+ &fs->id,
+ &fs->parent,
+ &maj, &min,
++#ifdef HAVE_SCANF_MS_MODIFIER
+ &fs->root,
+ &fs->target,
+ &fs->vfs_optstr,
++#else
++ fs->root,
++ fs->target,
++ fs->vfs_optstr,
++#endif
+ &end);
+
+ if (rc >= 7 && end > 0)
+@@ -167,9 +202,15 @@ static int mnt_parse_mountinfo_line(stru
+ UL_SCNsA" " /* (9) source */
+ UL_SCNsA, /* (10) fs options (fs specific) */
+
++#ifdef HAVE_SCANF_MS_MODIFIER
+ &fstype,
+ &src,
+ &fs->fs_optstr);
++#else
++ fstype,
++ src,
++ fs->fs_optstr);
++#endif
+
+ if (rc >= 10) {
+ fs->flags |= MNT_FS_KERNEL;