stdio: ISO C 23: Define _PRINTF_NAN_LEN_MAX.

* lib/stdio.in.h (_PRINTF_NAN_LEN_MAX): New macro.
* m4/stdio_h.m4 (gl_STDIO_H): Invoke gl_MUSL_LIBC.
* modules/stdio (Files): Add m4/musl.m4.
* tests/test-stdio.c: Check that _PRINTF_NAN_LEN_MAX is defined.
Include nan.h, macros.h.
(main): Check the value of _PRINTF_NAN_LEN_MAX.
* modules/stdio-tests (Files): Add tests/nan.h, tests/macros.h,
m4/exponentd.m4.
(configure.ac): Invoke gl_DOUBLE_EXPONENT_LOCATION.

1 files changed, 32 insertions, 0 deletions

diff --git a/tests/test-stdio.c b/tests/test-stdio.c
index a3b0a3e2ba..9794f4d856 100644
--- a/tests/test-stdio.c
+++ b/tests/test-stdio.c
@@ -23,6 +23,9 @@
 /* Check that the various SEEK_* macros are defined.  */
 int sk[] = { SEEK_CUR, SEEK_END, SEEK_SET };
 
+/* Check that the _PRINTF_NAN_LEN_MAX macro is defined.  */
+int pnlm[] = { _PRINTF_NAN_LEN_MAX };
+
 /* Check that NULL can be passed through varargs as a pointer type,
    per POSIX 2008.  */
 static_assert (sizeof NULL == sizeof (void *));
@@ -34,8 +37,37 @@ size_t t3;
 ssize_t t4;
 va_list t5;
 
+#include <string.h>
+
+#include "nan.h"
+#include "macros.h"
+
 int
 main (void)
 {
+#if defined DBL_EXPBIT0_WORD && defined DBL_EXPBIT0_BIT
+  /* Check the value of _PRINTF_NAN_LEN_MAX.  */
+  {
+    #define NWORDS \
+      ((sizeof (double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
+    typedef union { double value; unsigned int word[NWORDS]; } memory_double;
+
+    double value1;
+    memory_double value2;
+    char buf[64];
+
+    value1 = NaNd();
+    sprintf (buf, "%g", value1);
+    ASSERT (strlen (buf) <= _PRINTF_NAN_LEN_MAX);
+
+    value2.value = NaNd ();
+    #if DBL_EXPBIT0_BIT == 20
+    value2.word[DBL_EXPBIT0_WORD] ^= 0x54321;
+    #endif
+    sprintf (buf, "%g", value2.value);
+    ASSERT (strlen (buf) <= _PRINTF_NAN_LEN_MAX);
+  }
+#endif
+
   return 0;
 }