[PATCH v2] Replace copysign (0,-1) with -0.0 in initializer

[Maciej W. Rozycki]

On Tue, 17 Dec 2024, Joseph Myers wrote:

> >  I was not able to track down a definitive standards reference requiring 
> > IEEE 754 compiler implementations to respect the sign of zero in literals, 
> > would you or anyone else be able to point me at one?
> 
> C23 Annex F binds unary '-' to the 'negate' operation (which is defined in 
> IEEE 754 as a quiet-computational operation that affects only the sign 
> bit, even for NaNs), and specifies that literal conversions (bound to 
> convertFromDecimalCharacter, though the detailed syntax is given in the C 
> standard) are correctly rounded up to at least CR_DECIMAL_DIG digits.

 Thank you.  C99/C11 instead just say:

"The unary minus (-) operator provides the unary minus (-) operation 
recommended in the Appendix to IEC 60559."

-- would you agree that this is also sufficient for this particular use 
case (noting that I reckon IEEE 754 unary minus might be arithmetic at the 
implementer's discretion, which doesn't matter for static initialisers 
though, and certainly not for 0.0 operand)?

  Maciej