C2x scanf %wN, %wfN support

ISO C2x defines scanf length modifiers wN (for intN_t / int_leastN_t /
uintN_t / uint_leastN_t) and wfN (for int_fastN_t / uint_fastN_t).
Add support for those length modifiers, similar to the printf support
previously added.

Tested for x86_64 and x86.

4 files changed, 552 insertions, 0 deletions

diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 3866362bae..bacb795fed 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -243,6 +243,7 @@ tests := \
   tst-scanf-binary-c2x \
   tst-scanf-binary-gnu11 \
   tst-scanf-binary-gnu89 \
+  tst-scanf-intn \
   tst-scanf-round \
   tst-scanf-to_inpunct \
   tst-setvbuf1 \
diff --git a/stdio-common/tst-scanf-intn-main.c b/stdio-common/tst-scanf-intn-main.c
new file mode 100644
index 0000000000..fa0462a8de
--- /dev/null
+++ b/stdio-common/tst-scanf-intn-main.c
@@ -0,0 +1,479 @@
+/* Test scanf formats for intN_t, int_leastN_t and int_fastN_t types.
+   Copyright (C) 2023 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <wchar.h>
+
+#include <libc-diag.h>
+#include <support/check.h>
+
+/* GCC does not know the %wN or %wfN length modifiers before GCC 13.  */
+DIAG_PUSH_NEEDS_COMMENT;
+#if !__GNUC_PREREQ (13, 0)
+DIAG_IGNORE_NEEDS_COMMENT (12, "-Wformat");
+DIAG_IGNORE_NEEDS_COMMENT (12, "-Wformat-extra-args");
+#endif
+
+#define CHECK_SCANF1(EXPECTED, STR, FMT)				\
+  do									\
+    {									\
+      var = ((typeof (var)) 0xabababab);				\
+      int ret = SSCANF (L_(STR), L_(FMT), &var);			\
+      TEST_COMPARE (var, (EXPECTED));					\
+      TEST_COMPARE (ret, 1);						\
+    }									\
+  while (0)
+
+#define CHECK_SCANF1N(EXPECTED, STR, FMT)				\
+  do									\
+    {									\
+      var = ((typeof (var)) 0xabababab);				\
+      n = 123;								\
+      int ret = SSCANF (L_(STR), L_(FMT), &var, &n);			\
+      TEST_COMPARE (var, (EXPECTED));					\
+      TEST_COMPARE (n, STRLEN (L_(STR)));				\
+      TEST_COMPARE (ret, 1);						\
+    }									\
+  while (0)
+
+#define CHECK_SCANF_ERR(OK, STR, FMT, ...)				\
+  do									\
+    {									\
+      int ret = SSCANF (L_(STR), L_(FMT), __VA_ARGS__);			\
+      TEST_VERIFY (ret == (OK));					\
+      TEST_COMPARE (errno, EINVAL);					\
+    }									\
+  while (0)
+
+static void
+test_w8 (void)
+{
+  {
+    int8_t var, n;
+    CHECK_SCANF1 (42, "42", "%w8d");
+    CHECK_SCANF1N (42, "42", "%w8d%w8n");
+    CHECK_SCANF1 (-43, "-43", "%w8d");
+    CHECK_SCANF1 (42, "42", "%w8i");
+    CHECK_SCANF1 (-43, "-43", "%w8i");
+    CHECK_SCANF1 (123, "0b1111011", "%w8i");
+    CHECK_SCANF1 (127, "0x7f", "%w8i");
+    CHECK_SCANF1 (-19, "-023", "%w8i");
+  }
+  {
+    uint8_t var;
+    int8_t n;
+    CHECK_SCANF1 (123, "1111011", "%w8b");
+    CHECK_SCANF1 (19, "023", "%w8o");
+    CHECK_SCANF1 (50, "50", "%w8u");
+    CHECK_SCANF1 (65, "41", "%w8x");
+    CHECK_SCANF1N (65, "41", "%w8x%w8n");
+    CHECK_SCANF1 (66, "42", "%w8X");
+  }
+  {
+    int_least8_t var, n;
+    CHECK_SCANF1 (42, "42", "%w8d");
+    CHECK_SCANF1N (42, "42", "%w8d%w8n");
+    CHECK_SCANF1 (-43, "-43", "%w8d");
+    CHECK_SCANF1 (42, "42", "%w8i");
+    CHECK_SCANF1 (-43, "-43", "%w8i");
+    CHECK_SCANF1 (123, "0b1111011", "%w8i");
+    CHECK_SCANF1 (127, "0x7f", "%w8i");
+    CHECK_SCANF1 (-19, "-023", "%w8i");
+  }
+  {
+    uint_least8_t var;
+    int_least8_t n;
+    CHECK_SCANF1 (123, "1111011", "%w8b");
+    CHECK_SCANF1 (19, "023", "%w8o");
+    CHECK_SCANF1 (50, "50", "%w8u");
+    CHECK_SCANF1 (65, "41", "%w8x");
+    CHECK_SCANF1N (65, "41", "%w8x%w8n");
+    CHECK_SCANF1 (66, "42", "%w8X");
+  }
+}
+
+static void
+test_wf8 (void)
+{
+  {
+    int_fast8_t var, n;
+    CHECK_SCANF1 (42, "42", "%wf8d");
+    CHECK_SCANF1N (42, "42", "%wf8d%wf8n");
+    CHECK_SCANF1 (-43, "-43", "%wf8d");
+    CHECK_SCANF1 (42, "42", "%wf8i");
+    CHECK_SCANF1 (-43, "-43", "%wf8i");
+    CHECK_SCANF1 (123, "0b1111011", "%wf8i");
+    CHECK_SCANF1 (127, "0x7f", "%wf8i");
+    CHECK_SCANF1 (-19, "-023", "%wf8i");
+  }
+  {
+    uint_fast8_t var;
+    int_fast8_t n;
+    CHECK_SCANF1 (123, "1111011", "%wf8b");
+    CHECK_SCANF1 (19, "023", "%wf8o");
+    CHECK_SCANF1 (50, "50", "%wf8u");
+    CHECK_SCANF1 (65, "41", "%wf8x");
+    CHECK_SCANF1N (65, "41", "%wf8x%wf8n");
+    CHECK_SCANF1 (66, "42", "%wf8X");
+  }
+}
+
+static void
+test_w16 (void)
+{
+  {
+    int16_t var, n;
+    CHECK_SCANF1 (12345, "12345", "%w16d");
+    CHECK_SCANF1N (23456, "23456", "%w16d%w16n");
+    CHECK_SCANF1 (-10101, "-10101", "%w16d");
+    CHECK_SCANF1 (30000, "30000", "%w16i");
+    CHECK_SCANF1 (-19876, "-19876", "%w16i");
+    CHECK_SCANF1 (16384, "0b100000000000000", "%w16i");
+    CHECK_SCANF1 (32767, "0x7fff", "%w16i");
+    CHECK_SCANF1 (-16383, "-037777", "%w16i");
+  }
+  {
+    uint16_t var;
+    int16_t n;
+    CHECK_SCANF1 (32767, "111111111111111", "%w16b");
+    CHECK_SCANF1 (4095, "07777", "%w16o");
+    CHECK_SCANF1 (9999, "9999", "%w16u");
+    CHECK_SCANF1 (23456, "5ba0", "%w16x");
+    CHECK_SCANF1N (23456, "5ba0", "%w16x%w16n");
+    CHECK_SCANF1 (23457, "5ba1", "%w16X");
+  }
+  {
+    int_least16_t var, n;
+    CHECK_SCANF1 (12345, "12345", "%w16d");
+    CHECK_SCANF1N (23456, "23456", "%w16d%w16n");
+    CHECK_SCANF1 (-10101, "-10101", "%w16d");
+    CHECK_SCANF1 (30000, "30000", "%w16i");
+    CHECK_SCANF1 (-19876, "-19876", "%w16i");
+    CHECK_SCANF1 (16384, "0b100000000000000", "%w16i");
+    CHECK_SCANF1 (32767, "0x7fff", "%w16i");
+    CHECK_SCANF1 (-16383, "-037777", "%w16i");
+  }
+  {
+    uint_least16_t var;
+    int_least16_t n;
+    CHECK_SCANF1 (32767, "111111111111111", "%w16b");
+    CHECK_SCANF1 (4095, "07777", "%w16o");
+    CHECK_SCANF1 (9999, "9999", "%w16u");
+    CHECK_SCANF1 (23456, "5ba0", "%w16x");
+    CHECK_SCANF1N (23456, "5ba0", "%w16x%w16n");
+    CHECK_SCANF1 (23457, "5ba1", "%w16X");
+  }
+}
+
+static void
+test_wf16 (void)
+{
+  {
+    int_fast16_t var, n;
+    CHECK_SCANF1 (12345, "12345", "%wf16d");
+    CHECK_SCANF1N (23456, "23456", "%wf16d%wf16n");
+    CHECK_SCANF1 (-10101, "-10101", "%wf16d");
+    CHECK_SCANF1 (30000, "30000", "%wf16i");
+    CHECK_SCANF1 (-19876, "-19876", "%wf16i");
+    CHECK_SCANF1 (16384, "0b100000000000000", "%wf16i");
+    CHECK_SCANF1 (32767, "0x7fff", "%wf16i");
+    CHECK_SCANF1 (-16383, "-037777", "%wf16i");
+  }
+  {
+    uint_fast16_t var;
+    int_fast16_t n;
+    CHECK_SCANF1 (32767, "111111111111111", "%wf16b");
+    CHECK_SCANF1 (4095, "07777", "%wf16o");
+    CHECK_SCANF1 (9999, "9999", "%wf16u");
+    CHECK_SCANF1 (23456, "5ba0", "%wf16x");
+    CHECK_SCANF1N (23456, "5ba0", "%wf16x%wf16n");
+    CHECK_SCANF1 (23457, "5ba1", "%wf16X");
+  }
+#if INT_FAST16_MAX >= INT32_MAX
+  {
+    int_fast16_t var, n;
+    CHECK_SCANF1 (1234567, "1234567", "%wf16d");
+    CHECK_SCANF1N (2345678, "2345678", "%wf16d%wf16n");
+    CHECK_SCANF1 (-1010101, "-1010101", "%wf16d");
+    CHECK_SCANF1 (3000000, "3000000", "%wf16i");
+    CHECK_SCANF1 (-98765432, "-98765432", "%wf16i");
+    CHECK_SCANF1 (1048576, "0b100000000000000000000", "%wf16i");
+    CHECK_SCANF1 (1048575, "0xfffff", "%wf16i");
+    CHECK_SCANF1 (-1048575, "-03777777", "%wf16i");
+  }
+  {
+    uint_fast16_t var;
+    int_fast16_t n;
+    CHECK_SCANF1 (1234567, "100101101011010000111", "%wf16b");
+    CHECK_SCANF1 (1048575, "03777777", "%wf16o");
+    CHECK_SCANF1 (999999, "999999", "%wf16u");
+    CHECK_SCANF1 (987654, "f1206", "%wf16x");
+    CHECK_SCANF1N (987654, "f1206", "%wf16x%wf16n");
+    CHECK_SCANF1 (987655, "f1207", "%wf16X");
+  }
+#endif
+#if INT_FAST16_MAX >= INT64_MAX
+  {
+    int_fast16_t var, n;
+    CHECK_SCANF1 (123456789012LL, "123456789012", "%wf16d");
+    CHECK_SCANF1N (234567890123LL, "234567890123", "%wf16d%wf16n");
+    CHECK_SCANF1 (-10101010101LL, "-10101010101", "%wf16d");
+    CHECK_SCANF1 (3000000000000000LL, "3000000000000000", "%wf16i");
+    CHECK_SCANF1 (-9876543210LL, "-9876543210", "%wf16i");
+    CHECK_SCANF1 (1LL << 40, "0b10000000000000000000000000000000000000000",
+		  "%wf16i");
+    CHECK_SCANF1 (1LL << 41, "0x20000000000", "%wf16i");
+    CHECK_SCANF1 (-(1LL << 42), "-0100000000000000", "%wf16i");
+  }
+  {
+    uint_fast16_t var;
+    int_fast16_t n;
+    CHECK_SCANF1 (123456789012ULL, "1110010111110100110010001101000010100",
+		  "%wf16b");
+    CHECK_SCANF1 (1ULL << 40, "20000000000000", "%wf16o");
+    CHECK_SCANF1 (999999999999ULL, "999999999999", "%wf16u");
+    CHECK_SCANF1 (9876543210ULL, "24cb016ea", "%wf16x");
+    CHECK_SCANF1N (9876543210ULL, "24cb016ea", "%wf16x%wf16n");
+    CHECK_SCANF1 (9876543211ULL, "24cb016eb", "%wf16X");
+  }
+#endif
+}
+
+static void
+test_w32 (void)
+{
+  {
+    int32_t var, n;
+    CHECK_SCANF1 (1234567, "1234567", "%w32d");
+    CHECK_SCANF1N (2345678, "2345678", "%w32d%w32n");
+    CHECK_SCANF1 (-1010101, "-1010101", "%w32d");
+    CHECK_SCANF1 (3000000, "3000000", "%w32i");
+    CHECK_SCANF1 (-98765432, "-98765432", "%w32i");
+    CHECK_SCANF1 (1048576, "0b100000000000000000000", "%w32i");
+    CHECK_SCANF1 (1048575, "0xfffff", "%w32i");
+    CHECK_SCANF1 (-1048575, "-03777777", "%w32i");
+  }
+  {
+    uint32_t var;
+    int32_t n;
+    CHECK_SCANF1 (1234567, "100101101011010000111", "%w32b");
+    CHECK_SCANF1 (1048575, "03777777", "%w32o");
+    CHECK_SCANF1 (999999, "999999", "%w32u");
+    CHECK_SCANF1 (987654, "f1206", "%w32x");
+    CHECK_SCANF1N (987654, "f1206", "%w32x%w32n");
+    CHECK_SCANF1 (987655, "f1207", "%w32X");
+  }
+  {
+    int_least32_t var, n;
+    CHECK_SCANF1 (1234567, "1234567", "%w32d");
+    CHECK_SCANF1N (2345678, "2345678", "%w32d%w32n");
+    CHECK_SCANF1 (-1010101, "-1010101", "%w32d");
+    CHECK_SCANF1 (3000000, "3000000", "%w32i");
+    CHECK_SCANF1 (-98765432, "-98765432", "%w32i");
+    CHECK_SCANF1 (1048576, "0b100000000000000000000", "%w32i");
+    CHECK_SCANF1 (1048575, "0xfffff", "%w32i");
+    CHECK_SCANF1 (-1048575, "-03777777", "%w32i");
+  }
+  {
+    uint_least32_t var;
+    int_least32_t n;
+    CHECK_SCANF1 (1234567, "100101101011010000111", "%w32b");
+    CHECK_SCANF1 (1048575, "03777777", "%w32o");
+    CHECK_SCANF1 (999999, "999999", "%w32u");
+    CHECK_SCANF1 (987654, "f1206", "%w32x");
+    CHECK_SCANF1N (987654, "f1206", "%w32x%w32n");
+    CHECK_SCANF1 (987655, "f1207", "%w32X");
+  }
+}
+
+static void
+test_wf32 (void)
+{
+  {
+    int_fast32_t var, n;
+    CHECK_SCANF1 (1234567, "1234567", "%wf32d");
+    CHECK_SCANF1N (2345678, "2345678", "%wf32d%wf32n");
+    CHECK_SCANF1 (-1010101, "-1010101", "%wf32d");
+    CHECK_SCANF1 (3000000, "3000000", "%wf32i");
+    CHECK_SCANF1 (-98765432, "-98765432", "%wf32i");
+    CHECK_SCANF1 (1048576, "0b100000000000000000000", "%wf32i");
+    CHECK_SCANF1 (1048575, "0xfffff", "%wf32i");
+    CHECK_SCANF1 (-1048575, "-03777777", "%wf32i");
+  }
+  {
+    uint_fast32_t var;
+    int_fast32_t n;
+    CHECK_SCANF1 (1234567, "100101101011010000111", "%wf32b");
+    CHECK_SCANF1 (1048575, "03777777", "%wf32o");
+    CHECK_SCANF1 (999999, "999999", "%wf32u");
+    CHECK_SCANF1 (987654, "f1206", "%wf32x");
+    CHECK_SCANF1N (987654, "f1206", "%wf32x%wf32n");
+    CHECK_SCANF1 (987655, "f1207", "%wf32X");
+  }
+#if INT_FAST32_MAX >= INT64_MAX
+  {
+    int_fast32_t var, n;
+    CHECK_SCANF1 (123456789012LL, "123456789012", "%wf32d");
+    CHECK_SCANF1N (234567890123LL, "234567890123", "%wf32d%wf32n");
+    CHECK_SCANF1 (-10101010101LL, "-10101010101", "%wf32d");
+    CHECK_SCANF1 (3000000000000000LL, "3000000000000000", "%wf32i");
+    CHECK_SCANF1 (-9876543210LL, "-9876543210", "%wf32i");
+    CHECK_SCANF1 (1LL << 40, "0b10000000000000000000000000000000000000000",
+		  "%wf32i");
+    CHECK_SCANF1 (1LL << 41, "0x20000000000", "%wf32i");
+    CHECK_SCANF1 (-(1LL << 42), "-0100000000000000", "%wf32i");
+  }
+  {
+    uint_fast32_t var;
+    int_fast32_t n;
+    CHECK_SCANF1 (123456789012ULL, "1110010111110100110010001101000010100",
+		  "%wf32b");
+    CHECK_SCANF1 (1ULL << 40, "20000000000000", "%wf32o");
+    CHECK_SCANF1 (999999999999ULL, "999999999999", "%wf32u");
+    CHECK_SCANF1 (9876543210ULL, "24cb016ea", "%wf32x");
+    CHECK_SCANF1N (9876543210ULL, "24cb016ea", "%wf32x%wf32n");
+    CHECK_SCANF1 (9876543211ULL, "24cb016eb", "%wf32X");
+  }
+#endif
+}
+
+static void
+test_w64 (void)
+{
+  {
+    int64_t var, n;
+    CHECK_SCANF1 (123456789012LL, "123456789012", "%w64d");
+    CHECK_SCANF1N (234567890123LL, "234567890123", "%w64d%w64n");
+    CHECK_SCANF1 (-10101010101LL, "-10101010101", "%w64d");
+    CHECK_SCANF1 (3000000000000000LL, "3000000000000000", "%w64i");
+    CHECK_SCANF1 (-9876543210LL, "-9876543210", "%w64i");
+    CHECK_SCANF1 (1LL << 40, "0b10000000000000000000000000000000000000000",
+		  "%w64i");
+    CHECK_SCANF1 (1LL << 41, "0x20000000000", "%w64i");
+    CHECK_SCANF1 (-(1LL << 42), "-0100000000000000", "%w64i");
+  }
+  {
+    uint64_t var;
+    int64_t n;
+    CHECK_SCANF1 (123456789012ULL, "1110010111110100110010001101000010100",
+		  "%w64b");
+    CHECK_SCANF1 (1ULL << 40, "20000000000000", "%w64o");
+    CHECK_SCANF1 (999999999999ULL, "999999999999", "%w64u");
+    CHECK_SCANF1 (9876543210ULL, "24cb016ea", "%w64x");
+    CHECK_SCANF1N (9876543210ULL, "24cb016ea", "%w64x%w64n");
+    CHECK_SCANF1 (9876543211ULL, "24cb016eb", "%w64X");
+  }
+  {
+    int_least64_t var, n;
+    CHECK_SCANF1 (123456789012LL, "123456789012", "%w64d");
+    CHECK_SCANF1N (234567890123LL, "234567890123", "%w64d%w64n");
+    CHECK_SCANF1 (-10101010101LL, "-10101010101", "%w64d");
+    CHECK_SCANF1 (3000000000000000LL, "3000000000000000", "%w64i");
+    CHECK_SCANF1 (-9876543210LL, "-9876543210", "%w64i");
+    CHECK_SCANF1 (1LL << 40, "0b10000000000000000000000000000000000000000",
+		  "%w64i");
+    CHECK_SCANF1 (1LL << 41, "0x20000000000", "%w64i");
+    CHECK_SCANF1 (-(1LL << 42), "-0100000000000000", "%w64i");
+  }
+  {
+    uint_least64_t var;
+    int_least64_t n;
+    CHECK_SCANF1 (123456789012ULL, "1110010111110100110010001101000010100",
+		  "%w64b");
+    CHECK_SCANF1 (1ULL << 40, "20000000000000", "%w64o");
+    CHECK_SCANF1 (999999999999ULL, "999999999999", "%w64u");
+    CHECK_SCANF1 (9876543210ULL, "24cb016ea", "%w64x");
+    CHECK_SCANF1N (9876543210ULL, "24cb016ea", "%w64x%w64n");
+    CHECK_SCANF1 (9876543211ULL, "24cb016eb", "%w64X");
+  }
+}
+
+static void
+test_wf64 (void)
+{
+  {
+    int_fast64_t var, n;
+    CHECK_SCANF1 (123456789012LL, "123456789012", "%wf64d");
+    CHECK_SCANF1N (234567890123LL, "234567890123", "%wf64d%wf64n");
+    CHECK_SCANF1 (-10101010101LL, "-10101010101", "%wf64d");
+    CHECK_SCANF1 (3000000000000000LL, "3000000000000000", "%wf64i");
+    CHECK_SCANF1 (-9876543210LL, "-9876543210", "%wf64i");
+    CHECK_SCANF1 (1LL << 40, "0b10000000000000000000000000000000000000000",
+		  "%wf64i");
+    CHECK_SCANF1 (1LL << 41, "0x20000000000", "%wf64i");
+    CHECK_SCANF1 (-(1LL << 42), "-0100000000000000", "%wf64i");
+  }
+  {
+    uint_fast64_t var;
+    int_fast64_t n;
+    CHECK_SCANF1 (123456789012ULL, "1110010111110100110010001101000010100",
+		  "%wf64b");
+    CHECK_SCANF1 (1ULL << 40, "20000000000000", "%wf64o");
+    CHECK_SCANF1 (999999999999ULL, "999999999999", "%wf64u");
+    CHECK_SCANF1 (9876543210ULL, "24cb016ea", "%wf64x");
+    CHECK_SCANF1N (9876543210ULL, "24cb016ea", "%wf64x%wf64n");
+    CHECK_SCANF1 (9876543211ULL, "24cb016eb", "%wf64X");
+  }
+}
+
+static int
+do_test (void)
+{
+  int a, b;
+  test_w8 ();
+  test_wf8 ();
+  test_w16 ();
+  test_wf16 ();
+  test_w32 ();
+  test_wf32 ();
+  test_w64 ();
+  test_wf64 ();
+  /* Bad N in %wN and %wfN are required to produce an error return (of
+     the number of input items assigned) from scanf functions (and can
+     also be seen to be invalid at compile time).  */
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (13, "-Wformat");
+  DIAG_IGNORE_NEEDS_COMMENT (13, "-Wformat-extra-args");
+  CHECK_SCANF_ERR (0, "1", "%w1d", &a);
+  CHECK_SCANF_ERR (0, "1", "%w123d", &a);
+  CHECK_SCANF_ERR (0, "1", "%w99999999999999999999d", &a);
+  CHECK_SCANF_ERR (0, "1", "%wf1d", &a);
+  CHECK_SCANF_ERR (0, "1", "%wf123d", &a);
+  CHECK_SCANF_ERR (0, "1", "%wf99999999999999999999d", &a);
+  CHECK_SCANF_ERR (1, "1 1", "%d %w1d", &a, &b);
+  CHECK_SCANF_ERR (1, "1 1", "%d %w123d", &a, &b);
+  CHECK_SCANF_ERR (1, "1 1", "%d %w99999999999999999999d", &a, &b);
+  CHECK_SCANF_ERR (1, "1 1", "%d %wf1d", &a, &b);
+  CHECK_SCANF_ERR (1, "1 1", "%d %wf123d", &a, &b);
+  CHECK_SCANF_ERR (1, "1 1", "%d %wf99999999999999999999d", &a, &b);
+  CHECK_SCANF_ERR (0, "1", "%1$w1d", &a);
+  CHECK_SCANF_ERR (0, "1", "%1$w123d", &a);
+  CHECK_SCANF_ERR (0, "1", "%1$w99999999999999999999d", &a);
+  CHECK_SCANF_ERR (0, "1", "%1$wf1d", &a);
+  CHECK_SCANF_ERR (0, "1", "%1$wf123d", &a);
+  CHECK_SCANF_ERR (0, "1", "%1$wf99999999999999999999d", &a);
+  DIAG_POP_NEEDS_COMMENT;
+  return 0;
+}
+
+DIAG_POP_NEEDS_COMMENT;
+
+#include <support/test-driver.c>
diff --git a/stdio-common/tst-scanf-intn.c b/stdio-common/tst-scanf-intn.c
new file mode 100644
index 0000000000..876eda30ee
--- /dev/null
+++ b/stdio-common/tst-scanf-intn.c
@@ -0,0 +1,24 @@
+/* Test scanf formats for intN_t, int_leastN_t and int_fastN_t types.
+   Narrow string version.
+   Copyright (C) 2023 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
+   <https://www.gnu.org/licenses/>.  */
+
+#define SSCANF sscanf
+#define STRLEN strlen
+#define L_(C) C
+
+#include <tst-scanf-intn-main.c>
diff --git a/stdio-common/vfscanf-internal.c b/stdio-common/vfscanf-internal.c
index 9b1197d751..cacb9668ba 100644
--- a/stdio-common/vfscanf-internal.c
+++ b/stdio-common/vfscanf-internal.c
@@ -381,6 +381,7 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
   while (*f != '\0')
     {
       unsigned int argpos;
+      bool is_fast;
       /* Extract the next argument, which is of type TYPE.
 	 For a %N$... spec, this is the Nth argument from the beginning;
 	 otherwise it is the next argument after the state now in ARG.  */
@@ -602,6 +603,53 @@ __vfscanf_internal (FILE *s, const char *format, va_list argptr,
 	  else if (sizeof (ptrdiff_t) > sizeof (int))
 	    flags |= LONG;
 	  break;
+	case L_('w'):
+	  {
+	    is_fast = false;
+	    if (*f == L_('f'))
+	      {
+		++f;
+		is_fast = true;
+	      }
+	    int bitwidth = 0;
+	    if (ISDIGIT (*f))
+	      bitwidth = read_int (&f);
+	    if (is_fast)
+	      switch (bitwidth)
+		{
+		case 8:
+		  bitwidth = INT_FAST8_WIDTH;
+		  break;
+		case 16:
+		  bitwidth = INT_FAST16_WIDTH;
+		  break;
+		case 32:
+		  bitwidth = INT_FAST32_WIDTH;
+		  break;
+		case 64:
+		  bitwidth = INT_FAST64_WIDTH;
+		  break;
+		}
+	    switch (bitwidth)
+	      {
+	      case 8:
+		flags |= CHAR;
+		break;
+	      case 16:
+		flags |= SHORT;
+		break;
+	      case 32:
+		break;
+	      case 64:
+		flags |= LONGDBL | LONG;
+		break;
+	      default:
+		/* ISO C requires this error to be detected.  */
+		__set_errno (EINVAL);
+		goto errout;
+	      }
+	  }
+	  break;
 	default:
 	  /* Not a recognized modifier.  Backup.  */
 	  --f;