From: Bruno Haible <bruno@clisp.org>
Date: Tue, 22 May 2007 01:07:46 +0000 (+0000)
Subject: Stricter check for printf result for NaN arguments.
X-Git-Tag: cvs-readonly~353
X-Git-Url: http://erislabs.org.uk/gitweb/?a=commitdiff_plain;h=17ccaa9d86f36720593a6d75f277657177a6d8a9;p=gnulib.git

Stricter check for printf result for NaN arguments.
---

diff --git a/ChangeLog b/ChangeLog
index 555ab9274..ef36f7454 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2007-05-21  Bruno Haible  <bruno@clisp.org>
+
+	* m4/printf.m4 (gl_PRINTF_INFINITE, gl_PRINTF_INFINITE_LONG_DOUBLE):
+	Check also the output for NaN arguments. When cross-compiling, guess
+	no on IRIX.
+	* lib/vasnprintf.c: Update comments.
+	* tests/test-vasnprintf-posix.c (strisnan): New function.
+	(test_function): Use it.
+	* tests/test-vasprintf-posix.c (strisnan): New function.
+	(test_function): Use it.
+	* tests/test-snprintf-posix.h (strisnan): New function.
+	(test_function): Use it.
+	* tests/test-sprintf-posix.h (strisnan): New function.
+	(test_function): Use it.
+	Reported by Eric Blake.
+
 2007-05-20  Bruno Haible  <bruno@clisp.org>
 
 	* m4/frexpl.m4 (gl_FUNC_FREXPL_WORKS): Add test for large finite
diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c
index bc5834fa9..c60888cde 100644
--- a/lib/vasnprintf.c
+++ b/lib/vasnprintf.c
@@ -1297,17 +1297,16 @@ VASNPRINTF (CHAR_T *resultbuf, size_t *lengthp, const CHAR_T *format, va_list ar
 # if NEED_PRINTF_INFINITE_DOUBLE
 			 || (a.arg[dp->arg_index].type == TYPE_DOUBLE
 			     /* The systems (mingw) which produce wrong output
-				for Inf and -Inf also do so for NaN and -0.0.
-				Therefore we treat these cases here as well.  */
+				for Inf, -Inf, and NaN also do so for -0.0.
+				Therefore we treat this case here as well.  */
 			     && is_infinite_or_zero (a.arg[dp->arg_index].a.a_double))
 # endif
 # if NEED_PRINTF_LONG_DOUBLE
 			 || a.arg[dp->arg_index].type == TYPE_LONGDOUBLE
 # elif NEED_PRINTF_INFINITE_LONG_DOUBLE
 			 || (a.arg[dp->arg_index].type == TYPE_LONGDOUBLE
-			     /* The systems which produce wrong output for Inf
-				and -Inf also do so for NaN.  Therefore treat
-				this case here as well.  */
+			     /* Some systems produce wrong output for Inf,
+				-Inf, and NaN.  */
 			     && is_infinitel (a.arg[dp->arg_index].a.a_longdouble))
 # endif
 			))
diff --git a/m4/printf.m4 b/m4/printf.m4
index fef64443a..a03f4a0b3 100644
--- a/m4/printf.m4
+++ b/m4/printf.m4
@@ -1,4 +1,4 @@
-# printf.m4 serial 12
+# printf.m4 serial 13
 dnl Copyright (C) 2003, 2007 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -124,8 +124,8 @@ changequote([,])dnl
     ])
 ])
 
-dnl Test whether the *printf family of functions supports infinite 'double'
-dnl arguments in the %f, %e, %g directives. (ISO C99, POSIX:2001)
+dnl Test whether the *printf family of functions supports infinite and NaN
+dnl 'double' arguments in the %f, %e, %g directives. (ISO C99, POSIX:2001)
 dnl Result is gl_cv_func_printf_infinite.
 
 AC_DEFUN([gl_PRINTF_INFINITE],
@@ -138,7 +138,26 @@ AC_DEFUN([gl_PRINTF_INFINITE],
       AC_TRY_RUN([
 #include <stdio.h>
 #include <string.h>
+static int
+strisnan (const char *string, size_t start_index, size_t end_index)
+{
+  if (start_index < end_index)
+    {
+      if (string[start_index] == '-')
+        start_index++;
+      if (start_index + 3 <= end_index
+          && memcmp (string + start_index, "nan", 3) == 0)
+        {
+          start_index += 3;
+          if (start_index == end_index
+              || (string[start_index] == '(' && string[end_index - 1] == ')'))
+            return 1;
+        }
+    }
+  return 0;
+}
 static char buf[100];
+static double zero = 0.0;
 int main ()
 {
   if (sprintf (buf, "%f", 1.0 / 0.0) < 0
@@ -147,18 +166,27 @@ int main ()
   if (sprintf (buf, "%f", -1.0 / 0.0) < 0
       || (strcmp (buf, "-inf") != 0 && strcmp (buf, "-infinity") != 0))
     return 1;
+  if (sprintf (buf, "%f", zero / zero) < 0
+      || !strisnan (buf, 0, strlen (buf)))
+    return 1;
   if (sprintf (buf, "%e", 1.0 / 0.0) < 0
       || (strcmp (buf, "inf") != 0 && strcmp (buf, "infinity") != 0))
     return 1;
   if (sprintf (buf, "%e", -1.0 / 0.0) < 0
       || (strcmp (buf, "-inf") != 0 && strcmp (buf, "-infinity") != 0))
     return 1;
+  if (sprintf (buf, "%e", zero / zero) < 0
+      || !strisnan (buf, 0, strlen (buf)))
+    return 1;
   if (sprintf (buf, "%g", 1.0 / 0.0) < 0
       || (strcmp (buf, "inf") != 0 && strcmp (buf, "infinity") != 0))
     return 1;
   if (sprintf (buf, "%g", -1.0 / 0.0) < 0
       || (strcmp (buf, "-inf") != 0 && strcmp (buf, "-infinity") != 0))
     return 1;
+  if (sprintf (buf, "%g", zero / zero) < 0
+      || !strisnan (buf, 0, strlen (buf)))
+    return 1;
   return 0;
 }], [gl_cv_func_printf_infinite=yes], [gl_cv_func_printf_infinite=no],
       [
@@ -175,8 +203,6 @@ changequote(,)dnl
                                # Guess yes on HP-UX >= 11.
          hpux[7-9]* | hpux10*) gl_cv_func_printf_infinite="guessing no";;
          hpux*)                gl_cv_func_printf_infinite="guessing yes";;
-                               # Guess yes on IRIX >= 6.5.
-         irix6.5)              gl_cv_func_printf_infinite="guessing yes";;
                                # Guess yes on NetBSD >= 3.
          netbsd[1-2]* | netbsdelf[1-2]* | netbsdaout[1-2]* | netbsdcoff[1-2]*)
                                gl_cv_func_printf_infinite="guessing no";;
@@ -191,8 +217,8 @@ changequote([,])dnl
     ])
 ])
 
-dnl Test whether the *printf family of functions supports infinite 'long double'
-dnl arguments in the %f, %e, %g directives. (ISO C99, POSIX:2001)
+dnl Test whether the *printf family of functions supports infinite and NaN
+dnl 'long double' arguments in the %f, %e, %g directives. (ISO C99, POSIX:2001)
 dnl Result is gl_cv_func_printf_infinite_long_double.
 
 AC_DEFUN([gl_PRINTF_INFINITE_LONG_DOUBLE],
@@ -208,7 +234,26 @@ AC_DEFUN([gl_PRINTF_INFINITE_LONG_DOUBLE],
           AC_TRY_RUN([
 #include <stdio.h>
 #include <string.h>
+static int
+strisnan (const char *string, size_t start_index, size_t end_index)
+{
+  if (start_index < end_index)
+    {
+      if (string[start_index] == '-')
+        start_index++;
+      if (start_index + 3 <= end_index
+          && memcmp (string + start_index, "nan", 3) == 0)
+        {
+          start_index += 3;
+          if (start_index == end_index
+              || (string[start_index] == '(' && string[end_index - 1] == ')'))
+            return 1;
+        }
+    }
+  return 0;
+}
 static char buf[100];
+static long double zeroL = 0.0L;
 int main ()
 {
   if (sprintf (buf, "%Lf", 1.0L / 0.0L) < 0
@@ -217,18 +262,27 @@ int main ()
   if (sprintf (buf, "%Lf", -1.0L / 0.0L) < 0
       || (strcmp (buf, "-inf") != 0 && strcmp (buf, "-infinity") != 0))
     return 1;
+  if (sprintf (buf, "%Lf", zeroL / zeroL) < 0
+      || !strisnan (buf, 0, strlen (buf)))
+    return 1;
   if (sprintf (buf, "%Le", 1.0L / 0.0L) < 0
       || (strcmp (buf, "inf") != 0 && strcmp (buf, "infinity") != 0))
     return 1;
   if (sprintf (buf, "%Le", -1.0L / 0.0L) < 0
       || (strcmp (buf, "-inf") != 0 && strcmp (buf, "-infinity") != 0))
     return 1;
+  if (sprintf (buf, "%Le", zeroL / zeroL) < 0
+      || !strisnan (buf, 0, strlen (buf)))
+    return 1;
   if (sprintf (buf, "%Lg", 1.0L / 0.0L) < 0
       || (strcmp (buf, "inf") != 0 && strcmp (buf, "infinity") != 0))
     return 1;
   if (sprintf (buf, "%Lg", -1.0L / 0.0L) < 0
       || (strcmp (buf, "-inf") != 0 && strcmp (buf, "-infinity") != 0))
     return 1;
+  if (sprintf (buf, "%Lg", zeroL / zeroL) < 0
+      || !strisnan (buf, 0, strlen (buf)))
+    return 1;
   return 0;
 }],
           [gl_cv_func_printf_infinite_long_double=yes],
@@ -247,8 +301,6 @@ changequote(,)dnl
                                    # Guess yes on HP-UX >= 11.
              hpux[7-9]* | hpux10*) gl_cv_func_printf_infinite_long_double="guessing no";;
              hpux*)                gl_cv_func_printf_infinite_long_double="guessing yes";;
-                                   # Guess yes on IRIX >= 6.5.
-             irix6.5)              gl_cv_func_printf_infinite_long_double="guessing yes";;
                                    # Guess yes on NetBSD >= 3.
              netbsd[1-2]* | netbsdelf[1-2]* | netbsdaout[1-2]* | netbsdcoff[1-2]*)
                                    gl_cv_func_printf_infinite_long_double="guessing no";;
@@ -895,7 +947,7 @@ dnl   AIX 5.2                        .  .  #  #  #  .  .  .  .  #  .  .  .  .  .
 dnl   AIX 4.3.2, 5.1                 #  .  #  #  #  #  .  .  .  #  .  .  .  .  .
 dnl   HP-UX 11.31                    .  .  .  .  #  .  .  .  .  #  .  .  #  #  .
 dnl   HP-UX 10.20, 11.{00,11,23}     #  .  .  .  #  #  .  .  .  #  .  .  #  #  #
-dnl   IRIX 6.5                       #  .  .  .  #  #  .  .  .  #  .  .  #  .  .
+dnl   IRIX 6.5                       #  .  #  #  #  #  .  .  .  #  .  .  #  .  .
 dnl   OSF/1 5.1                      #  .  #  #  #  #  .  .  .  #  .  .  #  .  #
 dnl   OSF/1 4.0d                     #  .  #  #  #  #  .  .  .  #  #  #  #  #  #
 dnl   NetBSD 4.0                     .  ?  ?  ?  ?  ?  .  .  ?  ?  .  .  .  ?  ?
diff --git a/tests/test-snprintf-posix.h b/tests/test-snprintf-posix.h
index aec450ea5..ed03fb446 100644
--- a/tests/test-snprintf-posix.h
+++ b/tests/test-snprintf-posix.h
@@ -49,6 +49,27 @@ strmatch (const char *pattern, const char *string)
   return 1;
 }
 
+/* Test whether string[start_index..end_index-1] is a valid textual
+   representation of NaN.  */
+static int
+strisnan (const char *string, size_t start_index, size_t end_index, int uppercase)
+{
+  if (start_index < end_index)
+    {
+      if (string[start_index] == '-')
+	start_index++;
+      if (start_index + 3 <= end_index
+	  && memcmp (string + start_index, uppercase ? "NAN" : "nan", 3) == 0)
+	{
+	  start_index += 3;
+	  if (start_index == end_index
+	      || (string[start_index] == '(' && string[end_index - 1] == ')'))
+	    return 1;
+	}
+    }
+  return 0;
+}
+	  
 static void
 test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
 {
@@ -176,8 +197,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%a %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -376,8 +396,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     /* "0000000nan 33" is not a valid result; see
        <http://lists.gnu.org/archive/html/bug-gnulib/2007-04/msg00107.html> */
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -442,8 +461,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%La %d", 0.0L / 0.0L, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -643,8 +661,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     /* "0000000nan 33" is not a valid result; see
        <http://lists.gnu.org/archive/html/bug-gnulib/2007-04/msg00107.html> */
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -804,8 +821,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%f %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -886,8 +902,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%020f %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1054,8 +1069,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%Lf %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1137,8 +1151,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%020Lf %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1217,8 +1230,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%F %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "NAN", 3) == 0
-		|| memcmp (result, "-NAN", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 1)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1313,8 +1325,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%LF %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "NAN", 3) == 0
-		|| memcmp (result, "-NAN", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 1)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1513,8 +1524,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%e %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1605,8 +1615,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%020e %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1774,8 +1783,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%Le %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1859,8 +1867,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%020Le %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -2038,8 +2045,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%g %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -2123,8 +2129,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%020g %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -2292,8 +2297,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%Lg %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -2377,8 +2381,7 @@ test_function (int (*my_snprintf) (char *, size_t, const char *, ...))
     int retval =
       my_snprintf (result, sizeof (result), "%020Lg %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
diff --git a/tests/test-sprintf-posix.h b/tests/test-sprintf-posix.h
index d1afd331a..6149dd78a 100644
--- a/tests/test-sprintf-posix.h
+++ b/tests/test-sprintf-posix.h
@@ -49,6 +49,27 @@ strmatch (const char *pattern, const char *string)
   return 1;
 }
 
+/* Test whether string[start_index..end_index-1] is a valid textual
+   representation of NaN.  */
+static int
+strisnan (const char *string, size_t start_index, size_t end_index, int uppercase)
+{
+  if (start_index < end_index)
+    {
+      if (string[start_index] == '-')
+	start_index++;
+      if (start_index + 3 <= end_index
+	  && memcmp (string + start_index, uppercase ? "NAN" : "nan", 3) == 0)
+	{
+	  start_index += 3;
+	  if (start_index == end_index
+	      || (string[start_index] == '(' && string[end_index - 1] == ')'))
+	    return 1;
+	}
+    }
+  return 0;
+}
+	  
 static void
 test_function (int (*my_sprintf) (char *, const char *, ...))
 {
@@ -162,8 +183,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%a %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -362,8 +382,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     /* "0000000nan 33" is not a valid result; see
        <http://lists.gnu.org/archive/html/bug-gnulib/2007-04/msg00107.html> */
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -428,8 +447,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%La %d", 0.0L / 0.0L, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -629,8 +647,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     /* "0000000nan 33" is not a valid result; see
        <http://lists.gnu.org/archive/html/bug-gnulib/2007-04/msg00107.html> */
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -790,8 +807,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%f %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -866,8 +882,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%020f %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1034,8 +1049,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%Lf %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1111,8 +1125,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%020Lf %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1191,8 +1204,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%F %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "NAN", 3) == 0
-		|| memcmp (result, "-NAN", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 1)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1287,8 +1299,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%LF %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "NAN", 3) == 0
-		|| memcmp (result, "-NAN", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 1)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1487,8 +1498,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%e %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1579,8 +1589,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%020e %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1748,8 +1757,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%Le %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -1833,8 +1841,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%020Le %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -2012,8 +2019,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%g %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -2097,8 +2103,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%020g %d", NaN (), 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -2266,8 +2271,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%Lg %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
@@ -2351,8 +2355,7 @@ test_function (int (*my_sprintf) (char *, const char *, ...))
     int retval =
       my_sprintf (result, "%020Lg %d", zero / zero, 33, 44, 55);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
   }
diff --git a/tests/test-vasnprintf-posix.c b/tests/test-vasnprintf-posix.c
index db39fbe84..9dcf481cc 100644
--- a/tests/test-vasnprintf-posix.c
+++ b/tests/test-vasnprintf-posix.c
@@ -74,6 +74,27 @@ strmatch (const char *pattern, const char *string)
   return 1;
 }
 
+/* Test whether string[start_index..end_index-1] is a valid textual
+   representation of NaN.  */
+static int
+strisnan (const char *string, size_t start_index, size_t end_index, int uppercase)
+{
+  if (start_index < end_index)
+    {
+      if (string[start_index] == '-')
+	start_index++;
+      if (start_index + 3 <= end_index
+	  && memcmp (string + start_index, uppercase ? "NAN" : "nan", 3) == 0)
+	{
+	  start_index += 3;
+	  if (start_index == end_index
+	      || (string[start_index] == '(' && string[end_index - 1] == ')'))
+	    return 1;
+	}
+    }
+  return 0;
+}
+	  
 static void
 test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
 {
@@ -228,8 +249,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%a %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -464,8 +484,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
     /* "0000000nan 33" is not a valid result; see
        <http://lists.gnu.org/archive/html/bug-gnulib/2007-04/msg00107.html> */
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -544,8 +563,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%La %d", 0.0L / 0.0L, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -781,8 +799,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
     /* "0000000nan 33" is not a valid result; see
        <http://lists.gnu.org/archive/html/bug-gnulib/2007-04/msg00107.html> */
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -960,8 +977,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%f %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -1054,8 +1070,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%020f %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -1242,8 +1257,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%Lf %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -1337,8 +1351,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%020Lf %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -1435,8 +1448,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%F %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "NAN", 3) == 0
-		|| memcmp (result, "-NAN", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 1)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -1553,8 +1565,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%LF %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "NAN", 3) == 0
-		|| memcmp (result, "-NAN", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 1)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -1776,8 +1787,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%e %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -1888,8 +1898,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%020e %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -2077,8 +2086,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%Le %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -2182,8 +2190,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%020Le %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -2381,8 +2388,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%g %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -2486,8 +2492,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%020g %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -2675,8 +2680,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%Lg %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
@@ -2780,8 +2784,7 @@ test_function (char * (*my_asnprintf) (char *, size_t *, const char *, ...))
       my_asnprintf (NULL, &length, "%020Lg %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (length == strlen (result));
     free (result);
diff --git a/tests/test-vasprintf-posix.c b/tests/test-vasprintf-posix.c
index aa8a0bb29..51aebdfcc 100644
--- a/tests/test-vasprintf-posix.c
+++ b/tests/test-vasprintf-posix.c
@@ -74,6 +74,27 @@ strmatch (const char *pattern, const char *string)
   return 1;
 }
 
+/* Test whether string[start_index..end_index-1] is a valid textual
+   representation of NaN.  */
+static int
+strisnan (const char *string, size_t start_index, size_t end_index, int uppercase)
+{
+  if (start_index < end_index)
+    {
+      if (string[start_index] == '-')
+	start_index++;
+      if (start_index + 3 <= end_index
+	  && memcmp (string + start_index, uppercase ? "NAN" : "nan", 3) == 0)
+	{
+	  start_index += 3;
+	  if (start_index == end_index
+	      || (string[start_index] == '(' && string[end_index - 1] == ')'))
+	    return 1;
+	}
+    }
+  return 0;
+}
+	  
 static void
 test_function (int (*my_asprintf) (char **, const char *, ...))
 {
@@ -209,8 +230,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%a %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -445,8 +465,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
     /* "0000000nan 33" is not a valid result; see
        <http://lists.gnu.org/archive/html/bug-gnulib/2007-04/msg00107.html> */
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -525,8 +544,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%La %d", 0.0L / 0.0L, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -762,8 +780,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
     /* "0000000nan 33" is not a valid result; see
        <http://lists.gnu.org/archive/html/bug-gnulib/2007-04/msg00107.html> */
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -941,8 +958,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%f %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -1035,8 +1051,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%020f %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -1223,8 +1238,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%Lf %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -1318,8 +1332,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%020Lf %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -1416,8 +1429,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%F %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "NAN", 3) == 0
-		|| memcmp (result, "-NAN", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 1)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -1534,8 +1546,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%LF %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "NAN", 3) == 0
-		|| memcmp (result, "-NAN", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 1)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -1757,8 +1768,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%e %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -1869,8 +1879,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%020e %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -2058,8 +2067,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%Le %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -2163,8 +2171,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%020Le %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -2362,8 +2369,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%g %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -2467,8 +2473,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%020g %d", NaN (), 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -2656,8 +2661,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%Lg %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) >= 3 + 3
-	    && (memcmp (result, "nan", 3) == 0
-		|| memcmp (result, "-nan", 4) == 0)
+	    && strisnan (result, 0, strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);
@@ -2761,8 +2765,7 @@ test_function (int (*my_asprintf) (char **, const char *, ...))
       my_asprintf (&result, "%020Lg %d", zero / zero, 33, 44, 55);
     ASSERT (result != NULL);
     ASSERT (strlen (result) == 20 + 3
-	    && (memcmp (result + strspn (result, " "), "nan", 3) == 0
-		|| memcmp (result + strspn (result, " "), "-nan", 4) == 0)
+	    && strisnan (result, strspn (result, " "), strlen (result) - 3, 0)
 	    && strcmp (result + strlen (result) - 3, " 33") == 0);
     ASSERT (retval == strlen (result));
     free (result);