[PATCH] Increase internal precision of ldbl-128ibm decimal printf

[Paul E. Murphy]

On 03/17/2016 05:16 PM, Joseph Myers wrote:
> On Thu, 17 Mar 2016, Paul E. Murphy wrote:
> 
>> When the signs differ, the precision of the conversion
>> could drop below 106 bits.  This strategy is
>> identical to the hexadecimal variant.
> 
> I assume this was user-visible in a release, in which case it should have 
> a bug filed in Bugzilla (if it doesn't already have one - I take it this 
> is distinct from bug 5268?).
> 
> It should also have a testcase included in the patch (there are several 
> tests in sysdeps/ieee754/ldbl-128ibm already for issues specific to this 
> format - various of which use unions to test issues that can't be tested 
> simply with 106-bit inputs GCC can represent, or where it's necessary to 
> examine the two halves of a long double result separately).
> 

This came up internally. I think it is similar, the comments would indicate
it is a 1 bit internal precision loss which this patch does address.

I will figure out how to update the tests to catch this, and give the magic
shift amount a name.

Thanks,
Paul