Make <inttypes.h> printf macros narrow arguments (bug 31470)

A late change in C23, the resolution to CD2 comment GB-108, specified
that <inttypes.h> macros such as PRId8 expand to formats such that,
when an argument is passed in the promoted type that isn't
representable in the original type such as int8_t corresponding to the
format, it gets converted to that type before printing.  (Previously,
the proper handling of such arguments was unclear; the case of direct
use of formats such as %hhd was clarified earlier in C23 development,
and had been fixed in glibc in 2006.)  Implement the change to use
formats such as "hhd" for the affected macros, with associated tests.

Tested for x86_64 and x86.

diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 8da164695fab07312095f2b76d8d54901a0f5359..da337cb4e18846661d6f74d840976ab4f2a47d08 100644 (file)
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -314,6 +314,7 @@ tests := \
   tst-popen2 \
   tst-printf-binary \
   tst-printf-intn \
+  tst-printf-macro \
   tst-printf-oct \
   tst-printf-round \
   tst-printfsz \

diff --git a/stdio-common/tst-printf-macro.c b/stdio-common/tst-printf-macro.c
new file mode 100644 (file)
index 0000000..100c6a4
--- /dev/null
+++ b/stdio-common/tst-printf-macro.c
@@ -0,0 +1,93 @@
+/* Test printf PRI* macro narrowing arguments.
+   Copyright (C) 2025 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 <inttypes.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <libc-diag.h>
+#include <support/check.h>
+
+#define CHECK_PRINTF(EXPECTED, FMT, ...)               \
+  do                                                   \
+    {                                                  \
+      int ret = snprintf (buf, sizeof buf, FMT,                \
+                         __VA_ARGS__);                 \
+      TEST_COMPARE_STRING (buf, EXPECTED);             \
+      TEST_COMPARE (ret, strlen (EXPECTED));           \
+    }                                                  \
+  while (0)
+
+_Static_assert (INT_FAST8_WIDTH == 8, "width of int_fast8_t");
+_Static_assert (UINT_FAST8_WIDTH == 8, "width of uint_fast8_t");
+
+static int
+do_test (void)
+{
+  char buf[1024];
+  CHECK_PRINTF ("-121", "%" PRId8, 1234567);
+  CHECK_PRINTF ("-121", "%" PRIdLEAST8, 1234567);
+  CHECK_PRINTF ("-121", "%" PRIdFAST8, 1234567);
+  CHECK_PRINTF ("-10617", "%" PRId16, 1234567);
+  CHECK_PRINTF ("-10617", "%" PRIdLEAST16, 1234567);
+  CHECK_PRINTF ("-121", "%" PRIi8, 1234567);
+  CHECK_PRINTF ("-121", "%" PRIiLEAST8, 1234567);
+  CHECK_PRINTF ("-121", "%" PRIiFAST8, 1234567);
+  CHECK_PRINTF ("-10617", "%" PRIi16, 1234567);
+  CHECK_PRINTF ("-10617", "%" PRIiLEAST16, 1234567);
+  CHECK_PRINTF ("207", "%" PRIo8, 1234567);
+  CHECK_PRINTF ("207", "%" PRIoLEAST8, 1234567);
+  CHECK_PRINTF ("207", "%" PRIoFAST8, 1234567);
+  CHECK_PRINTF ("153207", "%" PRIo16, 1234567);
+  CHECK_PRINTF ("153207", "%" PRIoLEAST16, 1234567);
+  CHECK_PRINTF ("135", "%" PRIu8, 1234567);
+  CHECK_PRINTF ("135", "%" PRIuLEAST8, 1234567);
+  CHECK_PRINTF ("135", "%" PRIuFAST8, 1234567);
+  CHECK_PRINTF ("54919", "%" PRIu16, 1234567);
+  CHECK_PRINTF ("54919", "%" PRIuLEAST16, 1234567);
+  CHECK_PRINTF ("87", "%" PRIx8, 1234567);
+  CHECK_PRINTF ("87", "%" PRIxLEAST8, 1234567);
+  CHECK_PRINTF ("87", "%" PRIxFAST8, 1234567);
+  CHECK_PRINTF ("d687", "%" PRIx16, 1234567);
+  CHECK_PRINTF ("d687", "%" PRIxLEAST16, 1234567);
+  CHECK_PRINTF ("87", "%" PRIX8, 1234567);
+  CHECK_PRINTF ("87", "%" PRIXLEAST8, 1234567);
+  CHECK_PRINTF ("87", "%" PRIXFAST8, 1234567);
+  CHECK_PRINTF ("D687", "%" PRIX16, 1234567);
+  CHECK_PRINTF ("D687", "%" PRIXLEAST16, 1234567);
+  /* GCC does not know the %b or %B formats before GCC 12.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if !__GNUC_PREREQ (12, 0)
+  DIAG_IGNORE_NEEDS_COMMENT (11, "-Wformat");
+  DIAG_IGNORE_NEEDS_COMMENT (11, "-Wformat-extra-args");
+#endif
+  CHECK_PRINTF ("10000111", "%" PRIb8, 1234567);
+  CHECK_PRINTF ("10000111", "%" PRIbLEAST8, 1234567);
+  CHECK_PRINTF ("10000111", "%" PRIbFAST8, 1234567);
+  CHECK_PRINTF ("1101011010000111", "%" PRIb16, 1234567);
+  CHECK_PRINTF ("1101011010000111", "%" PRIbLEAST16, 1234567);
+  CHECK_PRINTF ("10000111", "%" PRIB8, 1234567);
+  CHECK_PRINTF ("10000111", "%" PRIBLEAST8, 1234567);
+  CHECK_PRINTF ("10000111", "%" PRIBFAST8, 1234567);
+  CHECK_PRINTF ("1101011010000111", "%" PRIB16, 1234567);
+  CHECK_PRINTF ("1101011010000111", "%" PRIBLEAST16, 1234567);
+  DIAG_POP_NEEDS_COMMENT;
+  return 0;
+}
+
+#include <support/test-driver.c>

diff --git a/stdlib/inttypes.h b/stdlib/inttypes.h
index 9726abf5b1d31f5e3182885abb2eb7cc0a1b10f1..a244db0da83315b559525e1c6572564c8eab0bf1 100644 (file)
--- a/stdlib/inttypes.h
+++ b/stdlib/inttypes.h
@@ -51,97 +51,97 @@ typedef wchar_t __gwchar_t;
 /* Macros for printing format specifiers.  */
 
 /* Decimal notation.  */
-# define PRId8         "d"
-# define PRId16                "d"
+# define PRId8         "hhd"
+# define PRId16                "hd"
 # define PRId32                "d"
 # define PRId64                __PRI64_PREFIX "d"
 
-# define PRIdLEAST8    "d"
-# define PRIdLEAST16   "d"
+# define PRIdLEAST8    "hhd"
+# define PRIdLEAST16   "hd"
 # define PRIdLEAST32   "d"
 # define PRIdLEAST64   __PRI64_PREFIX "d"
 
-# define PRIdFAST8     "d"
+# define PRIdFAST8     "hhd"
 # define PRIdFAST16    __PRIPTR_PREFIX "d"
 # define PRIdFAST32    __PRIPTR_PREFIX "d"
 # define PRIdFAST64    __PRI64_PREFIX "d"
 
 
-# define PRIi8         "i"
-# define PRIi16                "i"
+# define PRIi8         "hhi"
+# define PRIi16                "hi"
 # define PRIi32                "i"
 # define PRIi64                __PRI64_PREFIX "i"
 
-# define PRIiLEAST8    "i"
-# define PRIiLEAST16   "i"
+# define PRIiLEAST8    "hhi"
+# define PRIiLEAST16   "hi"
 # define PRIiLEAST32   "i"
 # define PRIiLEAST64   __PRI64_PREFIX "i"
 
-# define PRIiFAST8     "i"
+# define PRIiFAST8     "hhi"
 # define PRIiFAST16    __PRIPTR_PREFIX "i"
 # define PRIiFAST32    __PRIPTR_PREFIX "i"
 # define PRIiFAST64    __PRI64_PREFIX "i"
 
 /* Octal notation.  */
-# define PRIo8         "o"
-# define PRIo16                "o"
+# define PRIo8         "hho"
+# define PRIo16                "ho"
 # define PRIo32                "o"
 # define PRIo64                __PRI64_PREFIX "o"
 
-# define PRIoLEAST8    "o"
-# define PRIoLEAST16   "o"
+# define PRIoLEAST8    "hho"
+# define PRIoLEAST16   "ho"
 # define PRIoLEAST32   "o"
 # define PRIoLEAST64   __PRI64_PREFIX "o"
 
-# define PRIoFAST8     "o"
+# define PRIoFAST8     "hho"
 # define PRIoFAST16    __PRIPTR_PREFIX "o"
 # define PRIoFAST32    __PRIPTR_PREFIX "o"
 # define PRIoFAST64    __PRI64_PREFIX "o"
 
 /* Unsigned integers.  */
-# define PRIu8         "u"
-# define PRIu16                "u"
+# define PRIu8         "hhu"
+# define PRIu16                "hu"
 # define PRIu32                "u"
 # define PRIu64                __PRI64_PREFIX "u"
 
-# define PRIuLEAST8    "u"
-# define PRIuLEAST16   "u"
+# define PRIuLEAST8    "hhu"
+# define PRIuLEAST16   "hu"
 # define PRIuLEAST32   "u"
 # define PRIuLEAST64   __PRI64_PREFIX "u"
 
-# define PRIuFAST8     "u"
+# define PRIuFAST8     "hhu"
 # define PRIuFAST16    __PRIPTR_PREFIX "u"
 # define PRIuFAST32    __PRIPTR_PREFIX "u"
 # define PRIuFAST64    __PRI64_PREFIX "u"
 
 /* lowercase hexadecimal notation.  */
-# define PRIx8         "x"
-# define PRIx16                "x"
+# define PRIx8         "hhx"
+# define PRIx16                "hx"
 # define PRIx32                "x"
 # define PRIx64                __PRI64_PREFIX "x"
 
-# define PRIxLEAST8    "x"
-# define PRIxLEAST16   "x"
+# define PRIxLEAST8    "hhx"
+# define PRIxLEAST16   "hx"
 # define PRIxLEAST32   "x"
 # define PRIxLEAST64   __PRI64_PREFIX "x"
 
-# define PRIxFAST8     "x"
+# define PRIxFAST8     "hhx"
 # define PRIxFAST16    __PRIPTR_PREFIX "x"
 # define PRIxFAST32    __PRIPTR_PREFIX "x"
 # define PRIxFAST64    __PRI64_PREFIX "x"
 
 /* UPPERCASE hexadecimal notation.  */
-# define PRIX8         "X"
-# define PRIX16                "X"
+# define PRIX8         "hhX"
+# define PRIX16                "hX"
 # define PRIX32                "X"
 # define PRIX64                __PRI64_PREFIX "X"
 
-# define PRIXLEAST8    "X"
-# define PRIXLEAST16   "X"
+# define PRIXLEAST8    "hhX"
+# define PRIXLEAST16   "hX"
 # define PRIXLEAST32   "X"
 # define PRIXLEAST64   __PRI64_PREFIX "X"
 
-# define PRIXFAST8     "X"
+# define PRIXFAST8     "hhX"
 # define PRIXFAST16    __PRIPTR_PREFIX "X"
 # define PRIXFAST32    __PRIPTR_PREFIX "X"
 # define PRIXFAST64    __PRI64_PREFIX "X"
@@ -166,17 +166,17 @@ typedef wchar_t __gwchar_t;
 
 /* Binary notation.  */
 # if __GLIBC_USE (ISOC23)
-#  define PRIb8                "b"
-#  define PRIb16       "b"
+#  define PRIb8                "hhb"
+#  define PRIb16       "hb"
 #  define PRIb32       "b"
 #  define PRIb64       __PRI64_PREFIX "b"
 
-#  define PRIbLEAST8   "b"
-#  define PRIbLEAST16  "b"
+#  define PRIbLEAST8   "hhb"
+#  define PRIbLEAST16  "hb"
 #  define PRIbLEAST32  "b"
 #  define PRIbLEAST64  __PRI64_PREFIX "b"
 
-#  define PRIbFAST8    "b"
+#  define PRIbFAST8    "hhb"
 #  define PRIbFAST16   __PRIPTR_PREFIX "b"
 #  define PRIbFAST32   __PRIPTR_PREFIX "b"
 #  define PRIbFAST64   __PRI64_PREFIX "b"
@@ -184,17 +184,17 @@ typedef wchar_t __gwchar_t;
 #  define PRIbMAX      __PRI64_PREFIX "b"
 #  define PRIbPTR      __PRIPTR_PREFIX "b"
 
-#  define PRIB8                "B"
-#  define PRIB16       "B"
+#  define PRIB8                "hhB"
+#  define PRIB16       "hB"
 #  define PRIB32       "B"
 #  define PRIB64       __PRI64_PREFIX "B"
 
-#  define PRIBLEAST8   "B"
-#  define PRIBLEAST16  "B"
+#  define PRIBLEAST8   "hhB"
+#  define PRIBLEAST16  "hB"
 #  define PRIBLEAST32  "B"
 #  define PRIBLEAST64  __PRI64_PREFIX "B"
 
-#  define PRIBFAST8    "B"
+#  define PRIBFAST8    "hhB"
 #  define PRIBFAST16   __PRIPTR_PREFIX "B"
 #  define PRIBFAST32   __PRIPTR_PREFIX "B"
 #  define PRIBFAST64   __PRI64_PREFIX "B"