selective linking of floating point support for *printf / *scanf

Joey Ye
Tue Sep 2 07:33:00 GMT 2014

On Sat, Aug 30, 2014 at 12:26 PM, Thomas Preud'homme
<> wrote:
>> From: Grissiom []
>> Sent: Friday, August 29, 2014 11:51 PM
>> Yes, it does.  The namespace reserved for the implementation is _[_A-Z].
>  > The namespace _[a-z] is still available for the user.  Which means the
>> user can declare their own _printf_float, and WE (as the implementation)
>> MUST NOT INTERFERE with it.  Since WE are the implementation, we should
>> use the namespace reserved for us, namely __printf_float.
> Mmmh indeed. I checked C99 and section 7.1.3 paragraph 1 third clause states:
> "All identifiers that begin with an underscore and either an uppercase letter or
> another underscore are always reserved for any use."
> Next clause express how single underscore not followed by a capital letter is
> reserved:
> "All identifiers that begin with an underscore are always reserved for use as identifiers
> with file scope in both the ordinary and tag name spaces."
Apparently newlib is not following this specification very well, as
there are symbols like _abc_r defined every where in current newlib. I
am not implying the spec should not be followed, but is newlib
designed to have a loose spec for the single underscore?

- Joey

> Since here we are talking about linkage, _printf_float is not safe according to the
> standard.
> Sigh.
> Ok I need to think about it. Thank you all for pointing out the problem with the
> current scheme.
> Best regards,
> Thomas

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