Refactor strtod parsing of NaN payloads

[Florian Weimer]

On 11/24/2015 03:04 PM, Joseph Myers wrote:
> On Tue, 24 Nov 2015, Florian Weimer wrote:
> 
>>> The point of this refactoring is so that a future change can call these 
>>> (libc) functions from the nan* functions in libm.  I don't think 
>>> internal_function is compatible with PLT calls from other libraries.
>>
>> internal_function is a bit of a misnomer, it just affects the calling
>> convention on some architectures.  Unlike attribute_hidden, it does not
>> interfere with linking, as long as the caller uses the same prototype
>> (with the internal_function attribute).
> 
> But is that calling convention change compatible with calling through the 
> PLT?

It only has an effect on i386, where it uses %eax, %edx, %ecx for
passing arguments.  %ebx isn't used, so it won't cause problems.  We use
the %eax-only variant in an installed header file, too.

Florian