[libcxx+newlib] nexttoward{f,l,} shims for _LDBL_EQ_DBL systems

Jonathan Roelofs jonathan@codesourcery.com
Tue Dec 2 18:55:00 GMT 2014


No. I've been told by one of my coworkers that nexttowardf cannot be implemented 
correctly on top of nextafterf. For that one we'll need a different 
implementation, perhaps we can copy the one in musl?... I'm not sure if the 
license is compatible with doing that.

Everything in this patch aside from the nexttowardf implementation is ready to 
go as far as I'm concerned. Craig, how about on your end?



On 12/2/14 11:45 AM, JF Bastien wrote:
> Is this change ready to land?
> On Wed, Sep 24, 2014 at 9:38 AM, Jonathan Roelofs
> <jonathan@codesourcery.com> wrote:
>> Craig,
>> Thanks for the review!
>> On 9/23/14 7:17 PM, Craig Howland wrote:
>>> On 09/23/2014 04:33 PM, Jonathan Roelofs wrote:
>>>> Please see the attached patch.
>>> Needs a ChangeLog entry.  Missing the patch for libm/common/Makefile.am.
>> Oops. I'm not very familiar with Newlib processes, so please let me know if
>> I'm missing other things that you'd normally expect from such an upstream
>> submission.... For example, some of my co-workers reminded me to also update
>> COPYING.NEWLIB, and add copyright headers to the new files.
>>> Operationally, all looks OK, but aesthetically, the use of casting is
>>> inconsistent.  For example:
>>> +long double
>>> +nexttowardl (long double x, long double y)
>>> +{
>>> +  return nextafter((double)x, (double)y);
>>> +}
>>> The x and y arguments are cast to double to pass to nextafter(), but the
>>> return
>>> value is not cast to long double.  It works OK, but could be confusing.
>>> Are the
>>> casts intended to highlight the spots where the double/long double
>>> equality is
>>> required?
>> Yeah, that was my intent.
>>> If so, it would probably be better to either cast in all places where
>>> it is theoretically needed, or to just leave them out.  The other existing
>>> functions of this style left all of them out (i.e. no casts from ld to d
>>> or d to
>>> ld)--see, for example, libm/common/nextafterl.c.  I suggest that the
>>> precedent
>>> is the better way.
>> Agreed, consistency is probably better.
>> Attached is a new version of this patch with these things addressed, and
>> I've added another similar shim for log2l.
>> Cheers,
>> Jon
>>> Craig
>> --
>> Jon Roelofs
>> jonathan@codesourcery.com
>> CodeSourcery / Mentor Embedded

Jon Roelofs
CodeSourcery / Mentor Embedded

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