Web lists-archives.com

strtod ("nan") returns negative NaN




Hi

I've found that strtod ("nan") returns negative NaN on Cygwin 64 bit.
https://cygwin.com/ml/cygwin/2018-08/msg00168.html

On Linux with glibc, both strtod ("nan")
and strtod ("-nan") return positive NaN.

So I've created the patch that behaves like glibc.
Both strtod ("nan") and strtod ("-nan") return positive NaN.

Sample code:
```
#include <stdio.h>
#include <stdlib.h>

int main (void)
{
  printf ("strtof (\"nan\", NULL) = %f\n", strtof ("nan", NULL));
  printf ("strtof (\"-nan\", NULL) = %f\n", strtof ("-nan", NULL));
  printf ("strtod (\"nan\", NULL) = %f\n", strtod ("nan", NULL));
  printf ("strtod (\"-nan\", NULL) = %f\n", strtod ("-nan", NULL));
  printf ("strtold (\"nan\", NULL) = %Lf\n", strtold ("nan", NULL));
  printf ("strtold (\"-nan\", NULL) = %Lf\n", strtold ("-nan", NULL));
}
```

The result of Cygwin (newlib) without my patch:
```
strtof ("nan", NULL) = nan
strtof ("-nan", NULL) = nan
strtod ("nan", NULL) = -nan
strtod ("-nan", NULL) = nan
strtold ("nan", NULL) = -nan
strtold ("-nan", NULL) = -nan
```

The result of Linux (glibc, Ubuntu 16.04):
```
strtof ("nan", NULL) = nan
strtof ("-nan", NULL) = nan
strtod ("nan", NULL) = nan
strtod ("-nan", NULL) = nan
strtold ("nan", NULL) = nan
strtold ("-nan", NULL) = nan
```

The result of FreeBSD 10.1 (BSD libc):
```
strtof ("nan", NULL) = nan
strtof ("-nan", NULL) = nan
strtod ("nan", NULL) = nan
strtod ("-nan", NULL) = nan
strtold ("nan", NULL) = nan
strtold ("-nan", NULL) = nan
```

The result of Cygwin (newlib) with my patch:
```
strtof ("nan", NULL) = nan
strtof ("-nan", NULL) = nan
strtod ("nan", NULL) = nan
strtod ("-nan", NULL) = nan
strtold ("nan", NULL) = nan
strtold ("-nan", NULL) = nan
```

Thanks.
>From 91cf4a20e0773f4a38d6d56b0867fe3725859e5e Mon Sep 17 00:00:00 2001
From: Masamichi Hosoda <trueroad@xxxxxxxxxxx>
Date: Tue, 14 Aug 2018 22:29:34 +0900
Subject: [PATCH 1/2] Fix strtod ("nan") returns negative NaN

The definition of qNaN for x86_64 and i386 was wrong.
So strtod ("nan") and strtold ("nan") returned negative NaN
instead of positive NaN.

strtof ("nan") returns positive NaN so it does not have this issue.

This commit fixes definition of qNaN for x86_64 and i386.
So strtod ("nan") and strtold ("nan") return positive NaN.
---
 newlib/libc/stdlib/gd_qnan.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/newlib/libc/stdlib/gd_qnan.h b/newlib/libc/stdlib/gd_qnan.h
index b775f82..8b0726a 100644
--- a/newlib/libc/stdlib/gd_qnan.h
+++ b/newlib/libc/stdlib/gd_qnan.h
@@ -26,6 +26,20 @@
 #elif defined(__IEEE_LITTLE_ENDIAN)
 
 #if !defined(__mips)
+#if defined (__x86_64__) || defined (__i386__)
+#define f_QNAN 0x7fc00000
+#define d_QNAN0 0x0
+#define d_QNAN1 0x7ff80000
+#define ld_QNAN0 0x0
+#define ld_QNAN1 0xc0000000
+#define ld_QNAN2 0x7fff
+#define ld_QNAN3 0x0
+#define ldus_QNAN0 0x0
+#define ldus_QNAN1 0x0
+#define ldus_QNAN2 0x0
+#define ldus_QNAN3 0xc000
+#define ldus_QNAN4 0x7fff
+#else
 #define f_QNAN 0xffc00000
 #define d_QNAN0 0x0
 #define d_QNAN1 0xfff80000
@@ -38,6 +52,7 @@
 #define ldus_QNAN2 0x0
 #define ldus_QNAN3 0xc000
 #define ldus_QNAN4 0xffff
+#endif
 #elif defined(__mips_nan2008)
 #define f_QNAN 0x7fc00000
 #define d_QNAN0 0x0
-- 
2.17.0

>From 7256702e5034b016b5114dd1a6c4c1a689a17816 Mon Sep 17 00:00:00 2001
From: Masamichi Hosoda <trueroad@xxxxxxxxxxx>
Date: Tue, 14 Aug 2018 23:12:49 +0900
Subject: [PATCH 2/2] Fix strtod ("-nan") returns negative NaN

On Linux,
glibc's strtod ("-nan") and strtold ("-nan") return positive NaN.

But, newlib's strtod ("-nan") returns negative NaN
because it inverted the sign with the presence of `-` character.
And, newlib's srtold ("-nan") returns negative NaN
because it set the sign bit with the presence of `-` character.

newlib's strtof ("-nan") returns positive NaN same as Linux glibc's.

This commit removes strtod's NaN sign inversion
and removes strtold's NaN sign bit setting.
So strtod ("-nan") and strtold ("-nan") return positive NaN
same as Linux glibc.
---
 newlib/libc/stdlib/strtod.c  | 1 +
 newlib/libc/stdlib/strtodg.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/newlib/libc/stdlib/strtod.c b/newlib/libc/stdlib/strtod.c
index 0cfa9e6..3b9fd26 100644
--- a/newlib/libc/stdlib/strtod.c
+++ b/newlib/libc/stdlib/strtod.c
@@ -451,6 +451,7 @@ _strtod_l (struct _reent *ptr, const char *__restrict s00, char **__restrict se,
 #ifndef No_Hex_NaN
 						}
 #endif
+					sign = 0;
 					goto ret;
 					}
 			  }
diff --git a/newlib/libc/stdlib/strtodg.c b/newlib/libc/stdlib/strtodg.c
index 4ac1f8e..cc2842b 100644
--- a/newlib/libc/stdlib/strtodg.c
+++ b/newlib/libc/stdlib/strtodg.c
@@ -585,6 +585,7 @@ _strtodg_l (struct _reent *p, const char *s00, char **se, FPI *fpi, Long *exp,
 					if (*s == '(') /*)*/
 						irv = hexnan(&s, fpi, bits);
 #endif
+					sign = 0;
 					goto infnanexp;
 					}
 			  }
-- 
2.17.0


--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple