diff --git a/ChangeLog b/ChangeLog
index c446abcd4e..8121c71714 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,68 @@
+2019-01-03  Zack Weinberg  <zackw@panix.com>
+
+	* include/features.h (__GLIBC_USE_DEPRECATED_SCANF): New __GLIBC_USE
+	parameter.  Only use deprecated scanf when __USE_GNU is defined
+	and __STDC_VERSION__ is less than 199901L or __cplusplus is less
+	than 201103L, whichever is relevant for the language being compiled.
+
+	* libio/stdio.h, libio/bits/stdio-ldbl.h: Decide whether to redirect
+	scanf, fscanf, sscanf, vscanf, vfscanf, and vsscanf to their
+	__isoc99_ variants based only on __GLIBC_USE (DEPRECATED_SCANF).
+	* wcsmbs/wchar.h: wcsmbs/bits/wchar-ldbl.h: Likewise for
+	wscanf, fwscanf, swscanf, vwscanf, vfwscanf, and vswscanf.
+
+	* libio/iovsscanf.c
+	* libio/fwscanf.c
+	* libio/iovswscanf.c
+	* libio/swscanf.c
+	* libio/vscanf.c
+	* libio/vwscanf.c
+	* libio/wscanf.c
+	* stdio-common/fscanf.c
+	* stdio-common/scanf.c
+	* stdio-common/vfscanf.c
+	* stdio-common/vfwscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-compat.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-fscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-fwscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-iovfscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-scanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-swscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-vfscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-vfwscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-vscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-vsscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-vswscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-vwscanf.c
+	* sysdeps/ieee754/ldbl-opt/nldbl-wscanf.c:
+	Override __GLIBC_USE_DEPRECATED_SCANF to 1.
+
+	* stdio-common/sscanf.c: Likewise.  Remove ldbl_hidden_def for __sscanf.
+	* stdio-common/isoc99_sscanf.c: Add libc_hidden_def for __isoc99_sscanf.
+	* include/stdio.h: Provide libc_hidden_proto for __isoc99_sscanf,
+	not sscanf.
+	[!__GLIBC_USE (DEPRECATED_SCANF)]: Define sscanf as __isoc99_scanf
+	with a preprocessor macro.
+
+	* stdio-common/bug21.c, stdio-common/scanf14.c:
+	Use %ms instead of %as, %mS instead of %aS, %m[] instead of %a[];
+	remove DIAG_IGNORE_NEEDS_COMMENT for -Wformat.
+	* stdio-common/scanf16.c: Likewise.  Add __attribute__ ((format (scanf)))
+	to xscanf, xfscanf, xsscanf.
+
+	* stdio-common/scanf14a.c: New copy of scanf14.c which still uses
+	%as, %aS, %a[].  Remove DIAG_IGNORE_NEEDS_COMMENT for -Wformat.
+	* stdio-common/scanf16a.c: New copy of scanf16.c which still uses
+	%as, %aS, %a[].  Add __attribute__ ((format (scanf))) to xscanf,
+	xfscanf, xsscanf.
+	* stdio-common/scanf15.c, stdio-common/scanf17.c: No need to
+	override feature selection macros or provide definitions of u_char etc.
+	* stdio-common/Makefile (tests): Add scanf14a and scanf16a.
+	(CFLAGS-scanf15.c, CFLAGS-scanf17.c): Remove.
+	(CFLAGS-scanf14a.c, CFLAGS-scanf16a.c): New.  Compile these files
+	with -std=gnu89.
+
 2019-01-03  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
 	* sysdeps/unix/sysv/linux/Makefile (sysdep_headers): Add
diff --git a/NEWS b/NEWS
index 4c8bc924ce..cc20102fda 100644
--- a/NEWS
+++ b/NEWS
@@ -68,6 +68,23 @@ Deprecated and removed features, and other changes affecting compatibility:
   used by the Linux kernel.  This affects the size and layout of those
   structures.
 
+* An archaic GNU extension to scanf, under which '%as', '%aS', and '%a[...]'
+  meant to scan a string and allocate space for it with malloc, is now
+  restricted to programs compiled in C89 or C++98 mode with _GNU_SOURCE
+  defined.  This extension conflicts with C99's use of '%a' to scan a
+  hexadecimal floating-point number, which is now available to programs
+  compiled as C99 or C++11 or higher, regardless of _GNU_SOURCE.
+
+  POSIX.1-2008 includes the feature of allocating a buffer for string input
+  with malloc, using the modifier letter 'm' instead.  Programs using
+  '%as', '%aS', or '%a[...]' with the old GNU meaning should change to
+  '%ms', '%mS', or '%m[...]' respectively.  Programs that wish to use the
+  C99 '%a' no longer need to avoid _GNU_SOURCE.
+
+  GCC's -Wformat warnings can detect most uses of this extension, as long
+  as all functions that call vscanf, vfscanf, or vsscanf are annotated with
+  __attribute__ ((format (scanf, ...))).
+
 Changes to build and runtime requirements:
 
 * Python 3.4 or later is required to build the GNU C Library.
diff --git a/include/features.h b/include/features.h
index dc9f8fa9ac..c9bc534e27 100644
--- a/include/features.h
+++ b/include/features.h
@@ -140,6 +140,7 @@
 #undef	__USE_FORTIFY_LEVEL
 #undef	__KERNEL_STRICT_NAMES
 #undef	__GLIBC_USE_DEPRECATED_GETS
+#undef	__GLIBC_USE_DEPRECATED_SCANF
 
 /* Suppress kernel-name space pollution unless user expressedly asks
    for it.  */
@@ -401,6 +402,27 @@
 # define __GLIBC_USE_DEPRECATED_GETS 1
 #endif
 
+/* GNU formerly extended the scanf functions with modified format
+   specifiers %as, %aS, and %a[...] that allocate a buffer for the
+   input using malloc.  This extension conflicts with ISO C99, which
+   defines %a as a standalone format specifier that reads a floating-
+   point number; moreover, POSIX.1-2008 provides the same feature
+   using the modifier letter 'm' instead (%ms, %mS, %m[...]).
+
+   We now follow C99 unless GNU extensions are active and the compiler
+   is specifically in C89 or C++98 mode (strict or not).  For
+   instance, with GCC, -std=gnu11 will have C99-compliant scanf with
+   or without -D_GNU_SOURCE, but -std=c89 -D_GNU_SOURCE will have the
+   old extension.  */
+#if defined __USE_GNU &&						\
+  (defined __cplusplus							\
+   ? (__cplusplus < 201103L && !defined __GXX_EXPERIMENTAL_CXX0X__)	\
+   : (!defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L))
+# define __GLIBC_USE_DEPRECATED_SCANF 1
+#else
+# define __GLIBC_USE_DEPRECATED_SCANF 0
+#endif
+
 /* Get definitions of __STDC_* predefined macros, if the compiler has
    not preincluded this header automatically.  */
 #include <stdc-predef.h>
diff --git a/include/stdio.h b/include/stdio.h
index 1b7da0f74d..65ccabbb05 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -64,9 +64,19 @@ extern int __isoc99_vscanf (const char *__restrict __format,
 extern int __isoc99_vsscanf (const char *__restrict __s,
 			     const char *__restrict __format,
 			     __gnuc_va_list __arg) __THROW;
+libc_hidden_proto (__isoc99_sscanf)
 libc_hidden_proto (__isoc99_vsscanf)
 libc_hidden_proto (__isoc99_vfscanf)
 
+/* Internal uses of sscanf should call the C99-compliant version.
+   Unfortunately, symbol redirection is not transitive, so the
+   __REDIRECT in the public header does not link up with the above
+   libc_hidden_proto.  Bridge the gap with a macro.  */
+#  if !__GLIBC_USE (DEPRECATED_SCANF)
+#   undef sscanf
+#   define sscanf __isoc99_sscanf
+#  endif
+
 /* Prototypes for compatibility functions.  */
 extern FILE *__new_tmpfile (void);
 extern FILE *__old_tmpfile (void);
@@ -171,7 +181,6 @@ libc_hidden_proto (__dprintf)
 libc_hidden_proto (fprintf)
 libc_hidden_proto (vfprintf)
 libc_hidden_proto (sprintf)
-libc_hidden_proto (sscanf)
 libc_hidden_proto (fwrite)
 libc_hidden_proto (perror)
 libc_hidden_proto (remove)
diff --git a/libio/bits/stdio-ldbl.h b/libio/bits/stdio-ldbl.h
index 18289e6b86..97ad168a04 100644
--- a/libio/bits/stdio-ldbl.h
+++ b/libio/bits/stdio-ldbl.h
@@ -26,9 +26,7 @@ __LDBL_REDIR_DECL (sprintf)
 __LDBL_REDIR_DECL (vfprintf)
 __LDBL_REDIR_DECL (vprintf)
 __LDBL_REDIR_DECL (vsprintf)
-#if defined __USE_ISOC99 && !defined __USE_GNU \
-    && !defined __REDIRECT \
-    && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+#if !__GLIBC_USE (DEPRECATED_SCANF)
 __LDBL_REDIR1_DECL (fscanf, __nldbl___isoc99_fscanf)
 __LDBL_REDIR1_DECL (scanf, __nldbl___isoc99_scanf)
 __LDBL_REDIR1_DECL (sscanf, __nldbl___isoc99_sscanf)
@@ -44,8 +42,7 @@ __LDBL_REDIR_DECL (vsnprintf)
 #endif
 
 #ifdef	__USE_ISOC99
-# if !defined __USE_GNU && !defined __REDIRECT \
-     && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+# if !__GLIBC_USE (DEPRECATED_SCANF)
 __LDBL_REDIR1_DECL (vfscanf, __nldbl___isoc99_vfscanf)
 __LDBL_REDIR1_DECL (vscanf, __nldbl___isoc99_vscanf)
 __LDBL_REDIR1_DECL (vsscanf, __nldbl___isoc99_vsscanf)
diff --git a/libio/fwscanf.c b/libio/fwscanf.c
index c316ef961d..24872f46ff 100644
--- a/libio/fwscanf.c
+++ b/libio/fwscanf.c
@@ -15,6 +15,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <libioP.h>
 #include <stdarg.h>
 #include <stdio.h>
diff --git a/libio/iovsscanf.c b/libio/iovsscanf.c
index 752eed96e3..a561eab87e 100644
--- a/libio/iovsscanf.c
+++ b/libio/iovsscanf.c
@@ -24,6 +24,11 @@
    This exception applies to code released by its copyright holders
    in files containing the exception.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "strfile.h"
 
 int
diff --git a/libio/iovswscanf.c b/libio/iovswscanf.c
index f584c963fa..669fdc12b6 100644
--- a/libio/iovswscanf.c
+++ b/libio/iovswscanf.c
@@ -24,6 +24,11 @@
    This exception applies to code released by its copyright holders
    in files containing the exception.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <wchar.h>
 #include "strfile.h"
 
diff --git a/libio/stdio.h b/libio/stdio.h
index 4cc5b24a31..b63ee88a77 100644
--- a/libio/stdio.h
+++ b/libio/stdio.h
@@ -399,13 +399,11 @@ extern int scanf (const char *__restrict __format, ...) __wur;
 extern int sscanf (const char *__restrict __s,
 		   const char *__restrict __format, ...) __THROW;
 
-#if defined __USE_ISOC99 && !defined __USE_GNU \
-    && (!defined __LDBL_COMPAT || !defined __REDIRECT) \
-    && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+/* For historical reasons, the C99-compliant versions of the scanf
+   functions are at alternative names.  When __LDBL_COMPAT is in
+   effect, this is handled in bits/stdio-ldbl.h.  */
+#if !__GLIBC_USE (DEPRECATED_SCANF) && !defined __LDBL_COMPAT
 # ifdef __REDIRECT
-/* For strict ISO C99 or POSIX compliance disallow %as, %aS and %a[
-   GNU extension which conflicts with valid %a followed by letter
-   s, S or [.  */
 extern int __REDIRECT (fscanf, (FILE *__restrict __stream,
 				const char *__restrict __format, ...),
 		       __isoc99_fscanf) __wur;
@@ -447,13 +445,9 @@ extern int vsscanf (const char *__restrict __s,
 		    const char *__restrict __format, __gnuc_va_list __arg)
      __THROW __attribute__ ((__format__ (__scanf__, 2, 0)));
 
-# if !defined __USE_GNU \
-     && (!defined __LDBL_COMPAT || !defined __REDIRECT) \
-     && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
-#  ifdef __REDIRECT
-/* For strict ISO C99 or POSIX compliance disallow %as, %aS and %a[
-   GNU extension which conflicts with valid %a followed by letter
-   s, S or [.  */
+/* Same redirection as above for the v*scanf family.  */
+# if !__GLIBC_USE (DEPRECATED_SCANF)
+#  if defined __REDIRECT && !defined __LDBL_COMPAT
 extern int __REDIRECT (vfscanf,
 		       (FILE *__restrict __s,
 			const char *__restrict __format, __gnuc_va_list __arg),
@@ -467,7 +461,7 @@ extern int __REDIRECT_NTH (vsscanf,
 			    const char *__restrict __format,
 			    __gnuc_va_list __arg), __isoc99_vsscanf)
      __attribute__ ((__format__ (__scanf__, 2, 0)));
-#  else
+#  elif !defined __REDIRECT
 extern int __isoc99_vfscanf (FILE *__restrict __s,
 			     const char *__restrict __format,
 			     __gnuc_va_list __arg) __wur;
diff --git a/libio/swscanf.c b/libio/swscanf.c
index e38b938b0b..5f529ef630 100644
--- a/libio/swscanf.c
+++ b/libio/swscanf.c
@@ -15,6 +15,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <stdarg.h>
 #include "strfile.h"
 
diff --git a/libio/vscanf.c b/libio/vscanf.c
index 936a2fdef8..342dc3effc 100644
--- a/libio/vscanf.c
+++ b/libio/vscanf.c
@@ -24,6 +24,11 @@
    This exception applies to code released by its copyright holders
    in files containing the exception.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "libioP.h"
 #include "stdio.h"
 
diff --git a/libio/vwscanf.c b/libio/vwscanf.c
index 0804175a81..696e4c5c99 100644
--- a/libio/vwscanf.c
+++ b/libio/vwscanf.c
@@ -24,6 +24,11 @@
    This exception applies to code released by its copyright holders
    in files containing the exception.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "libioP.h"
 #include <wchar.h>
 
diff --git a/libio/wscanf.c b/libio/wscanf.c
index ce8d3ed6b4..d4c7753e8e 100644
--- a/libio/wscanf.c
+++ b/libio/wscanf.c
@@ -15,6 +15,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <libioP.h>
 #include <stdarg.h>
 #include <stdio.h>
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 11556f2177..c38299c864 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -65,6 +65,8 @@ tests := tstscanf test_rdwr test-popen tstgetln test-fseek \
 	 tst-vfprintf-mbs-prec \
 	 tst-scanf-round \
 	 tst-renameat2 tst-bz11319 tst-bz11319-fortify2 \
+	 scanf14a scanf16a \
+
 
 test-srcs = tst-unbputc tst-printf tst-printfsz-islongdouble
 
@@ -146,13 +148,11 @@ CFLAGS-isoc99_scanf.c += -fexceptions
 CFLAGS-errlist.c += $(fno-unit-at-a-time)
 CFLAGS-siglist.c += $(fno-unit-at-a-time)
 
-# The following is a hack since we must compile scanf1{5,7}.c without any
-# GNU extension.  The latter are needed, though, when internal headers
-# are used.  So made sure we see the installed headers first.
-CFLAGS-scanf15.c += -I../libio -I../stdlib -I../wcsmbs -I../time -I../string \
-		   -I../wctype
-CFLAGS-scanf17.c += -I../libio -I../stdlib -I../wcsmbs -I../time -I../string \
-		   -I../wctype
+# scanf14a.c and scanf16a.c test a deprecated extension which is no
+# longer visible under most conformance levels; see the source files
+# for more detail.
+CFLAGS-scanf14a.c += -std=gnu89
+CFLAGS-scanf16a.c += -std=gnu89
 
 CFLAGS-bug3.c += -DOBJPFX=\"$(objpfx)\"
 CFLAGS-bug4.c += -DOBJPFX=\"$(objpfx)\"
diff --git a/stdio-common/bug21.c b/stdio-common/bug21.c
index 7a8c6a3542..1f06c0dab4 100644
--- a/stdio-common/bug21.c
+++ b/stdio-common/bug21.c
@@ -1,5 +1,4 @@
 #include <stdio.h>
-#include <libc-diag.h>
 
 static int
 do_test (void)
@@ -7,15 +6,7 @@ do_test (void)
   static const char buf[] = " ";
   char *str;
 
-  /* GCC in C99 mode treats %a as the C99 format expecting float *,
-     but glibc with _GNU_SOURCE treats %as as the GNU allocation
-     extension, so resulting in "warning: format '%a' expects argument
-     of type 'float *', but argument 3 has type 'char **'".  This
-     applies to the other %as, %aS and %a[] formats below as well.  */
-  DIAG_PUSH_NEEDS_COMMENT;
-  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
-  int r = sscanf (buf, "%as", &str);
-  DIAG_POP_NEEDS_COMMENT;
+  int r = sscanf (buf, "%ms", &str);
   printf ("%d %p\n", r, str);
 
   return r != -1 || str != NULL;
diff --git a/stdio-common/fscanf.c b/stdio-common/fscanf.c
index 4b8b26ad54..a210eafcab 100644
--- a/stdio-common/fscanf.c
+++ b/stdio-common/fscanf.c
@@ -15,6 +15,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <libioP.h>
 #include <stdarg.h>
 #include <stdio.h>
diff --git a/stdio-common/isoc99_sscanf.c b/stdio-common/isoc99_sscanf.c
index a6bfc66e95..a70c0c3f2f 100644
--- a/stdio-common/isoc99_sscanf.c
+++ b/stdio-common/isoc99_sscanf.c
@@ -33,3 +33,4 @@ __isoc99_sscanf (const char *s, const char *format, ...)
 
   return done;
 }
+libc_hidden_def (__isoc99_sscanf)
diff --git a/stdio-common/scanf.c b/stdio-common/scanf.c
index 1b69a656ef..9008d2bf97 100644
--- a/stdio-common/scanf.c
+++ b/stdio-common/scanf.c
@@ -15,6 +15,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <stdarg.h>
 #include <stdio.h>
 
diff --git a/stdio-common/scanf14.c b/stdio-common/scanf14.c
index 2bcd9c9893..8b271ae7cc 100644
--- a/stdio-common/scanf14.c
+++ b/stdio-common/scanf14.c
@@ -1,8 +1,28 @@
+/* Copyright (C) 2007-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <wchar.h>
-#include <libc-diag.h>
+
+#if __GLIBC_USE_DEPRECATED_SCANF
+# error "This file should not be compiled with deprecated scanf"
+#endif
 
 #define FAIL() \
   do {							\
@@ -24,14 +44,7 @@ main (void)
     FAIL ();
   else if (f != 0.25 || memcmp (c, "s x", 3) != 0)
     FAIL ();
-  /* GCC in C99 mode treats %a as the C99 format expecting float *,
-     but glibc with _GNU_SOURCE treats %as as the GNU allocation
-     extension, so resulting in "warning: format '%a' expects argument
-     of type 'float *', but argument 3 has type 'char **'".  This
-     applies to the other %as, %aS and %a[] formats below as well.  */
-  DIAG_PUSH_NEEDS_COMMENT;
-  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
-  if (sscanf (" 1.25s x", "%as%2c", &sp, c) != 2)
+  if (sscanf (" 1.25s x", "%ms%2c", &sp, c) != 2)
     FAIL ();
   else
     {
@@ -40,15 +53,11 @@ main (void)
       memset (sp, 'x', sizeof "1.25s");
       free (sp);
     }
-  DIAG_POP_NEEDS_COMMENT;
   if (sscanf (" 2.25s x", "%las%2c", &d, c) != 2)
     FAIL ();
   else if (d != 2.25 || memcmp (c, " x", 2) != 0)
     FAIL ();
-  /* See explanation above.  */
-  DIAG_PUSH_NEEDS_COMMENT;
-  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
-  if (sscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2)
+  if (sscanf (" 3.25S x", "%4mS%3c", &lsp, c) != 2)
     FAIL ();
   else
     {
@@ -57,7 +66,7 @@ main (void)
       memset (lsp, 'x', sizeof L"3.25");
       free (lsp);
     }
-  if (sscanf ("4.25[0-9.] x", "%a[0-9.]%8c", &sp, c) != 2)
+  if (sscanf ("4.25[0-9.] x", "%m[0-9.]%8c", &sp, c) != 2)
     FAIL ();
   else
     {
@@ -66,7 +75,6 @@ main (void)
       memset (sp, 'x', sizeof "4.25");
       free (sp);
     }
-  DIAG_POP_NEEDS_COMMENT;
   if (sscanf ("5.25[0-9.] x", "%la[0-9.]%2c", &d, c) != 2)
     FAIL ();
   else if (d != 5.25 || memcmp (c, " x", 2) != 0)
@@ -95,10 +103,7 @@ main (void)
 	FAIL ();
       if (fseek (fp, 0, SEEK_SET) != 0)
 	FAIL ();
-      /* See explanation above.  */
-      DIAG_PUSH_NEEDS_COMMENT;
-      DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
-      if (fscanf (fp, "%as%2c", &sp, c) != 2)
+      if (fscanf (fp, "%ms%2c", &sp, c) != 2)
 	FAIL ();
       else
 	{
@@ -107,16 +112,12 @@ main (void)
 	  memset (sp, 'x', sizeof "1.25s");
 	  free (sp);
 	}
-      DIAG_POP_NEEDS_COMMENT;
 
       if (freopen (fname, "r", stdin) == NULL)
 	FAIL ();
       else
 	{
-	  /* See explanation above.  */
-	  DIAG_PUSH_NEEDS_COMMENT;
-	  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
-	  if (scanf ("%as%2c", &sp, c) != 2)
+	  if (scanf ("%ms%2c", &sp, c) != 2)
 	    FAIL ();
 	  else
 	    {
@@ -125,7 +126,6 @@ main (void)
 	      memset (sp, 'x', sizeof "1.25s");
 	      free (sp);
 	    }
-	  DIAG_POP_NEEDS_COMMENT;
 	}
 
       fclose (fp);
diff --git a/stdio-common/scanf14a.c b/stdio-common/scanf14a.c
new file mode 100644
index 0000000000..5f95ecb693
--- /dev/null
+++ b/stdio-common/scanf14a.c
@@ -0,0 +1,143 @@
+/* Copyright (C) 2007-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This test exercises the deprecated GNU %as, %aS, and %a[...] scanf
+   modifiers, which are not available to programs compiled as C99
+   anymore; therefore, this file is compiled with -std=gnu89 and C99
+   syntax must not be used.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wchar.h>
+
+#if !__GLIBC_USE_DEPRECATED_SCANF
+# error "This file should be compiled with deprecated scanf"
+#endif
+
+
+#define FAIL() \
+  do {							\
+    result = 1;						\
+    printf ("test at line %d failed\n", __LINE__);	\
+  } while (0)
+
+int
+main (void)
+{
+  wchar_t *lsp;
+  char *sp;
+  float f;
+  double d;
+  char c[8];
+  int result = 0;
+
+  if (sscanf (" 0.25s x", "%e%3c", &f, c) != 2)
+    FAIL ();
+  else if (f != 0.25 || memcmp (c, "s x", 3) != 0)
+    FAIL ();
+  if (sscanf (" 1.25s x", "%as%2c", &sp, c) != 2)
+    FAIL ();
+  else
+    {
+      if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+	FAIL ();
+      memset (sp, 'x', sizeof "1.25s");
+      free (sp);
+    }
+  if (sscanf (" 2.25s x", "%las%2c", &d, c) != 2)
+    FAIL ();
+  else if (d != 2.25 || memcmp (c, " x", 2) != 0)
+    FAIL ();
+  if (sscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2)
+    FAIL ();
+  else
+    {
+      if (wcscmp (lsp, L"3.25") != 0 || memcmp (c, "S x", 3) != 0)
+	FAIL ();
+      memset (lsp, 'x', sizeof L"3.25");
+      free (lsp);
+    }
+  if (sscanf ("4.25[0-9.] x", "%a[0-9.]%8c", &sp, c) != 2)
+    FAIL ();
+  else
+    {
+      if (strcmp (sp, "4.25") != 0 || memcmp (c, "[0-9.] x", 8) != 0)
+	FAIL ();
+      memset (sp, 'x', sizeof "4.25");
+      free (sp);
+    }
+  if (sscanf ("5.25[0-9.] x", "%la[0-9.]%2c", &d, c) != 2)
+    FAIL ();
+  else if (d != 5.25 || memcmp (c, " x", 2) != 0)
+    FAIL ();
+
+  const char *tmpdir = getenv ("TMPDIR");
+  if (tmpdir == NULL || tmpdir[0] == '\0')
+    tmpdir = "/tmp";
+
+  char fname[strlen (tmpdir) + sizeof "/tst-scanf14.XXXXXX"];
+  sprintf (fname, "%s/tst-scanf14.XXXXXX", tmpdir);
+  if (fname == NULL)
+    FAIL ();
+
+  /* Create a temporary file.   */
+  int fd = mkstemp (fname);
+  if (fd == -1)
+    FAIL ();
+
+  FILE *fp = fdopen (fd, "w+");
+  if (fp == NULL)
+    FAIL ();
+  else
+    {
+      if (fputs (" 1.25s x", fp) == EOF)
+	FAIL ();
+      if (fseek (fp, 0, SEEK_SET) != 0)
+	FAIL ();
+      if (fscanf (fp, "%as%2c", &sp, c) != 2)
+	FAIL ();
+      else
+	{
+	  if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+	    FAIL ();
+	  memset (sp, 'x', sizeof "1.25s");
+	  free (sp);
+	}
+
+      if (freopen (fname, "r", stdin) == NULL)
+	FAIL ();
+      else
+	{
+	  if (scanf ("%as%2c", &sp, c) != 2)
+	    FAIL ();
+	  else
+	    {
+	      if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+		FAIL ();
+	      memset (sp, 'x', sizeof "1.25s");
+	      free (sp);
+	    }
+	}
+
+      fclose (fp);
+    }
+
+  remove (fname);
+
+  return result;
+}
diff --git a/stdio-common/scanf15.c b/stdio-common/scanf15.c
index a3ab15dea2..e658e42a2f 100644
--- a/stdio-common/scanf15.c
+++ b/stdio-common/scanf15.c
@@ -1,18 +1,29 @@
-#undef _GNU_SOURCE
-#define _XOPEN_SOURCE 600
-#undef _LIBC
-#undef _IO_MTSAFE_IO
-/* The following macro definitions are a hack.  They word around disabling
-   the GNU extension while still using a few internal headers.  */
-#define u_char unsigned char
-#define u_short unsigned short
-#define u_int unsigned int
-#define u_long unsigned long
+/* Copyright (C) 2007-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <wchar.h>
 
+#if __GLIBC_USE_DEPRECATED_SCANF
+# error "This file should not be compiled with deprecated scanf"
+#endif
+
 #define FAIL() \
   do {							\
     result = 1;						\
diff --git a/stdio-common/scanf16.c b/stdio-common/scanf16.c
index 3e3cb417f2..6e6f644e20 100644
--- a/stdio-common/scanf16.c
+++ b/stdio-common/scanf16.c
@@ -1,16 +1,37 @@
+/* Copyright (C) 2008-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <wchar.h>
 
+#if __GLIBC_USE_DEPRECATED_SCANF
+# error "This file should not be compiled with deprecated scanf"
+#endif
+
 #define FAIL() \
   do {							\
     result = 1;						\
     printf ("test at line %d failed\n", __LINE__);	\
   } while (0)
 
-static int
+static int __attribute__ ((format (scanf, 2, 3)))
 xsscanf (const char *str, const char *fmt, ...)
 {
   va_list ap;
@@ -20,7 +41,7 @@ xsscanf (const char *str, const char *fmt, ...)
   return ret;
 }
 
-static int
+static int __attribute__ ((format (scanf, 1, 2)))
 xscanf (const char *fmt, ...)
 {
   va_list ap;
@@ -30,7 +51,7 @@ xscanf (const char *fmt, ...)
   return ret;
 }
 
-static int
+static int __attribute__ ((format (scanf, 2, 3)))
 xfscanf (FILE *f, const char *fmt, ...)
 {
   va_list ap;
@@ -54,7 +75,7 @@ main (void)
     FAIL ();
   else if (f != 0.25 || memcmp (c, "s x", 3) != 0)
     FAIL ();
-  if (xsscanf (" 1.25s x", "%as%2c", &sp, c) != 2)
+  if (xsscanf (" 1.25s x", "%ms%2c", &sp, c) != 2)
     FAIL ();
   else
     {
@@ -67,7 +88,7 @@ main (void)
     FAIL ();
   else if (d != 2.25 || memcmp (c, " x", 2) != 0)
     FAIL ();
-  if (xsscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2)
+  if (xsscanf (" 3.25S x", "%4mS%3c", &lsp, c) != 2)
     FAIL ();
   else
     {
@@ -76,7 +97,7 @@ main (void)
       memset (lsp, 'x', sizeof L"3.25");
       free (lsp);
     }
-  if (xsscanf ("4.25[0-9.] x", "%a[0-9.]%8c", &sp, c) != 2)
+  if (xsscanf ("4.25[0-9.] x", "%m[0-9.]%8c", &sp, c) != 2)
     FAIL ();
   else
     {
@@ -113,7 +134,7 @@ main (void)
 	FAIL ();
       if (fseek (fp, 0, SEEK_SET) != 0)
 	FAIL ();
-      if (xfscanf (fp, "%as%2c", &sp, c) != 2)
+      if (xfscanf (fp, "%ms%2c", &sp, c) != 2)
 	FAIL ();
       else
 	{
@@ -127,7 +148,7 @@ main (void)
 	FAIL ();
       else
 	{
-	  if (xscanf ("%as%2c", &sp, c) != 2)
+	  if (xscanf ("%ms%2c", &sp, c) != 2)
 	    FAIL ();
 	  else
 	    {
diff --git a/stdio-common/scanf16a.c b/stdio-common/scanf16a.c
new file mode 100644
index 0000000000..09dc6582ef
--- /dev/null
+++ b/stdio-common/scanf16a.c
@@ -0,0 +1,173 @@
+/* Copyright (C) 2008-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* This test exercises the deprecated GNU %as, %aS, and %a[...] scanf
+   modifiers, which are not available to programs compiled as C99
+   anymore; therefore, this file is compiled with -std=gnu89 and C99
+   syntax must not be used.  */
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wchar.h>
+
+#if !__GLIBC_USE_DEPRECATED_SCANF
+# error "This file should be compiled with deprecated scanf"
+#endif
+
+#define FAIL() \
+  do {							\
+    result = 1;						\
+    printf ("test at line %d failed\n", __LINE__);	\
+  } while (0)
+
+static int __attribute__ ((format (scanf, 2, 3)))
+xsscanf (const char *str, const char *fmt, ...)
+{
+  va_list ap;
+  va_start (ap, fmt);
+  int ret = vsscanf (str, fmt, ap);
+  va_end (ap);
+  return ret;
+}
+
+static int __attribute__ ((format (scanf, 1, 2)))
+xscanf (const char *fmt, ...)
+{
+  va_list ap;
+  va_start (ap, fmt);
+  int ret = vscanf (fmt, ap);
+  va_end (ap);
+  return ret;
+}
+
+static int __attribute__ ((format (scanf, 2, 3)))
+xfscanf (FILE *f, const char *fmt, ...)
+{
+  va_list ap;
+  va_start (ap, fmt);
+  int ret = vfscanf (f, fmt, ap);
+  va_end (ap);
+  return ret;
+}
+
+int
+main (void)
+{
+  wchar_t *lsp;
+  char *sp;
+  float f;
+  double d;
+  char c[8];
+  int result = 0;
+
+  if (xsscanf (" 0.25s x", "%e%3c", &f, c) != 2)
+    FAIL ();
+  else if (f != 0.25 || memcmp (c, "s x", 3) != 0)
+    FAIL ();
+  if (xsscanf (" 1.25s x", "%as%2c", &sp, c) != 2)
+    FAIL ();
+  else
+    {
+      if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+	FAIL ();
+      memset (sp, 'x', sizeof "1.25s");
+      free (sp);
+    }
+  if (xsscanf (" 2.25s x", "%las%2c", &d, c) != 2)
+    FAIL ();
+  else if (d != 2.25 || memcmp (c, " x", 2) != 0)
+    FAIL ();
+  if (xsscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2)
+    FAIL ();
+  else
+    {
+      if (wcscmp (lsp, L"3.25") != 0 || memcmp (c, "S x", 3) != 0)
+	FAIL ();
+      memset (lsp, 'x', sizeof L"3.25");
+      free (lsp);
+    }
+  if (xsscanf ("4.25[0-9.] x", "%a[0-9.]%8c", &sp, c) != 2)
+    FAIL ();
+  else
+    {
+      if (strcmp (sp, "4.25") != 0 || memcmp (c, "[0-9.] x", 8) != 0)
+	FAIL ();
+      memset (sp, 'x', sizeof "4.25");
+      free (sp);
+    }
+  if (xsscanf ("5.25[0-9.] x", "%la[0-9.]%2c", &d, c) != 2)
+    FAIL ();
+  else if (d != 5.25 || memcmp (c, " x", 2) != 0)
+    FAIL ();
+
+  const char *tmpdir = getenv ("TMPDIR");
+  if (tmpdir == NULL || tmpdir[0] == '\0')
+    tmpdir = "/tmp";
+
+  char fname[strlen (tmpdir) + sizeof "/tst-scanf16.XXXXXX"];
+  sprintf (fname, "%s/tst-scanf16.XXXXXX", tmpdir);
+  if (fname == NULL)
+    FAIL ();
+
+  /* Create a temporary file.   */
+  int fd = mkstemp (fname);
+  if (fd == -1)
+    FAIL ();
+
+  FILE *fp = fdopen (fd, "w+");
+  if (fp == NULL)
+    FAIL ();
+  else
+    {
+      if (fputs (" 1.25s x", fp) == EOF)
+	FAIL ();
+      if (fseek (fp, 0, SEEK_SET) != 0)
+	FAIL ();
+      if (xfscanf (fp, "%as%2c", &sp, c) != 2)
+	FAIL ();
+      else
+	{
+	  if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+	    FAIL ();
+	  memset (sp, 'x', sizeof "1.25s");
+	  free (sp);
+	}
+
+      if (freopen (fname, "r", stdin) == NULL)
+	FAIL ();
+      else
+	{
+	  if (xscanf ("%as%2c", &sp, c) != 2)
+	    FAIL ();
+	  else
+	    {
+	      if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+		FAIL ();
+	      memset (sp, 'x', sizeof "1.25s");
+	      free (sp);
+	    }
+	}
+
+      fclose (fp);
+    }
+
+  remove (fname);
+
+  return result;
+}
diff --git a/stdio-common/scanf17.c b/stdio-common/scanf17.c
index b6c0e63ab0..c17c1dab4d 100644
--- a/stdio-common/scanf17.c
+++ b/stdio-common/scanf17.c
@@ -1,19 +1,30 @@
-#undef _GNU_SOURCE
-#define _XOPEN_SOURCE 600
-#undef _LIBC
-#undef _IO_MTSAFE_IO
-/* The following macro definitions are a hack.  They word around disabling
-   the GNU extension while still using a few internal headers.  */
-#define u_char unsigned char
-#define u_short unsigned short
-#define u_int unsigned int
-#define u_long unsigned long
+/* Copyright (C) 2008-2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <wchar.h>
 
+#if __GLIBC_USE_DEPRECATED_SCANF
+# error "This file should not be compiled with deprecated scanf"
+#endif
+
 #define FAIL() \
   do {							\
     result = 1;						\
diff --git a/stdio-common/sscanf.c b/stdio-common/sscanf.c
index a630fba409..59caf8df38 100644
--- a/stdio-common/sscanf.c
+++ b/stdio-common/sscanf.c
@@ -15,6 +15,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <stdarg.h>
 #include <libio/strfile.h>
 
@@ -34,6 +39,5 @@ __sscanf (const char *s, const char *format, ...)
 
   return done;
 }
-ldbl_hidden_def (__sscanf, sscanf)
 ldbl_strong_alias (__sscanf, sscanf)
 ldbl_strong_alias (__sscanf, _IO_sscanf)
diff --git a/stdio-common/vfscanf.c b/stdio-common/vfscanf.c
index f479909351..b1ef0fc718 100644
--- a/stdio-common/vfscanf.c
+++ b/stdio-common/vfscanf.c
@@ -15,6 +15,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <libioP.h>
 
 int
diff --git a/stdio-common/vfwscanf.c b/stdio-common/vfwscanf.c
index f8cfd81982..e75aafe39e 100644
--- a/stdio-common/vfwscanf.c
+++ b/stdio-common/vfwscanf.c
@@ -16,6 +16,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <libioP.h>
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-compat.c b/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
index 9c9646c4d2..76ef8a8f74 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-compat.c
@@ -17,6 +17,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+/* This file may define some of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include <stdarg.h>
 #include <stdio.h>
 #include <libio/strfile.h>
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-fscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-fscanf.c
index 1b768e306f..00507187f3 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-fscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-fscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-fwscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-fwscanf.c
index 27fc1a7271..65782894a2 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-fwscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-fwscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-iovfscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-iovfscanf.c
index 442c11c203..6ed9b48624 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-iovfscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-iovfscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-scanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-scanf.c
index bbab371cbe..c10da284f2 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-scanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-scanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c
index a771d49996..34e18be0a1 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-swscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-swscanf.c
index dd058f47ab..4076debc4e 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-swscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-swscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-vfscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-vfscanf.c
index f23465ee95..6f5ebc3045 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-vfscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-vfscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-vfwscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-vfwscanf.c
index be9febc9a0..0bef274726 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-vfwscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-vfwscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-vscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-vscanf.c
index e75907b905..38f654aa73 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-vscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-vscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-vsscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-vsscanf.c
index f5594c122c..33e10e49a9 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-vsscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-vsscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-vswscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-vswscanf.c
index bd4bb5131b..91c0d4cd4f 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-vswscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-vswscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-vwscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-vwscanf.c
index d39578ca4e..b3d0f1be18 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-vwscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-vwscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/sysdeps/ieee754/ldbl-opt/nldbl-wscanf.c b/sysdeps/ieee754/ldbl-opt/nldbl-wscanf.c
index 4ee3fdc15f..2689e27f06 100644
--- a/sysdeps/ieee754/ldbl-opt/nldbl-wscanf.c
+++ b/sysdeps/ieee754/ldbl-opt/nldbl-wscanf.c
@@ -1,3 +1,8 @@
+/* This file defines one of the deprecated scanf variants.  */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
 #include "nldbl-compat.h"
 
 int
diff --git a/wcsmbs/bits/wchar-ldbl.h b/wcsmbs/bits/wchar-ldbl.h
index c0b0c6e973..a3378014f3 100644
--- a/wcsmbs/bits/wchar-ldbl.h
+++ b/wcsmbs/bits/wchar-ldbl.h
@@ -27,9 +27,7 @@ __LDBL_REDIR_DECL (swprintf);
 __LDBL_REDIR_DECL (vfwprintf);
 __LDBL_REDIR_DECL (vwprintf);
 __LDBL_REDIR_DECL (vswprintf);
-# if defined __USE_ISOC99 && !defined __USE_GNU \
-     && !defined __REDIRECT \
-     && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+# if !__GLIBC_USE (DEPRECATED_SCANF)
 __LDBL_REDIR1_DECL (fwscanf, __nldbl___isoc99_fwscanf)
 __LDBL_REDIR1_DECL (wscanf, __nldbl___isoc99_wscanf)
 __LDBL_REDIR1_DECL (swscanf, __nldbl___isoc99_swscanf)
@@ -42,8 +40,7 @@ __LDBL_REDIR_DECL (swscanf);
 
 #ifdef __USE_ISOC99
 __LDBL_REDIR1_DECL (wcstold, wcstod);
-# if !defined __USE_GNU && !defined __REDIRECT \
-     && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+# if !__GLIBC_USE (DEPRECATED_SCANF)
 __LDBL_REDIR1_DECL (vfwscanf, __nldbl___isoc99_vfwscanf)
 __LDBL_REDIR1_DECL (vwscanf, __nldbl___isoc99_vwscanf)
 __LDBL_REDIR1_DECL (vswscanf, __nldbl___isoc99_vswscanf)
diff --git a/wcsmbs/wchar.h b/wcsmbs/wchar.h
index ddbe7100ee..20deca90bf 100644
--- a/wcsmbs/wchar.h
+++ b/wcsmbs/wchar.h
@@ -632,13 +632,11 @@ extern int swscanf (const wchar_t *__restrict __s,
 		    const wchar_t *__restrict __format, ...)
      __THROW /* __attribute__ ((__format__ (__wscanf__, 2, 3))) */;
 
-# if defined __USE_ISOC99 && !defined __USE_GNU \
-     && (!defined __LDBL_COMPAT || !defined __REDIRECT) \
-     && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+/* For historical reasons, the C99-compliant versions of the scanf
+   functions are at alternative names.  When __LDBL_COMPAT is in
+   effect, this is handled in bits/wchar-ldbl.h.  */
+#if !__GLIBC_USE (DEPRECATED_SCANF) && !defined __LDBL_COMPAT
 #  ifdef __REDIRECT
-/* For strict ISO C99 or POSIX compliance disallow %as, %aS and %a[
-   GNU extension which conflicts with valid %a followed by letter
-   s, S or [.  */
 extern int __REDIRECT (fwscanf, (__FILE *__restrict __stream,
 				 const wchar_t *__restrict __format, ...),
 		       __isoc99_fwscanf)