Re: [PATCH] Print sign of NaN values to nano-vfprintf.

On 11/12/2018 21:13, [email protected] wrote:
>> diff --git a/newlib/libc/stdio/nano-vfprintf_float.c
> b/newlib/libc/stdio/nano-vfprintf_float.c
>> index 98893e97b..071a09edc 100644
>> --- a/newlib/libc/stdio/nano-vfprintf_float.c
>> +++ b/newlib/libc/stdio/nano-vfprintf_float.c
>> @@ -213,6 +213,8 @@ _printf_float (struct _reent *data,
>>      }
>>    if (isnan (_fpvalue))
>>      {
>> +      if (_fpvalue < 0)
>> +	pdata->l_buf[0] = '-';
>>        if (code <= 'G')		/* 'A', 'E', 'F', or 'G'.  */
>>  	cp = "NAN";
> 
> This patch doesn't work, as a comparison of a NaN with anything should
> always return false. As per the main printf code, this can be done by
> checking the sign bit instead:
> 
> -      if (_fpvalue < 0)
> +      if (signbit (_fpvalue))
>  	pdata->l_buf[0] = '-';
> 
> Patch attached.
> 

That will work better for -0 as well.  LGTM

R.

> Cheers,
> Jon
> 
> 
> 0001-nano-vfprintf_float.c-Fix-check-if-negative-for-nans.patch
> 
> From 49593628a465af4e8409ed2aac142b9ed347156e Mon Sep 17 00:00:00 2001
> From: Jon Beniston <[email protected]>
> Date: Tue, 11 Dec 2018 21:03:03 +0000
> Subject: [PATCH] nano-vfprintf_float.c: Fix check if negative for nans.
> 
> ---
>  newlib/libc/stdio/nano-vfprintf_float.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/newlib/libc/stdio/nano-vfprintf_float.c b/newlib/libc/stdio/nano-vfprintf_float.c
> index 071a09edc..524f67a31 100644
> --- a/newlib/libc/stdio/nano-vfprintf_float.c
> +++ b/newlib/libc/stdio/nano-vfprintf_float.c
> @@ -39,6 +39,7 @@
>  #include <string.h>
>  #include <limits.h>
>  #include <stdint.h>
> +#include <math.h>
>  #include <wchar.h>
>  #include <sys/lock.h>
>  #include <stdarg.h>
> @@ -213,7 +214,7 @@ _printf_float (struct _reent *data,
>      }
>    if (isnan (_fpvalue))
>      {
> -      if (_fpvalue < 0)
> +      if (signbit (_fpvalue))
>  	pdata->l_buf[0] = '-';
>        if (code <= 'G')		/* 'A', 'E', 'F', or 'G'.  */
>  	cp = "NAN";
>