[Cfp-interest] (SC22WG14.14280) Is return of same type convertFormat or copy?

[Jim Thomas]

Would it be sufficient to append a sentence to F.3#3 (specified in Part 1) to say

“If the return expression of a return statement is evaluated to the floating-point format of the return type, it is implementation-defined whether a convertFormat operation is applied to the result of the return expression.”

Jim Thomas

> On Jun 11, 2016, at 3:16 PM, Joseph Myers <joseph at codesourcery.com> wrote:
> 
> TS 18661-1 says "Whether C assignment (6.5.16) (and conversion as if by 
> assignment) to the same format is an IEC 60559 convertFormat or copy 
> operation is implementation-defined, even if <fenv.h> defines the macro 
> FE_SNANS_ALWAYS_SIGNAL (F.2.1).".
> 
> Does this apply to function return, where the return type of the function 
> is the same as the type of the expression passed to the return statement 
> and no wider evaluation format is in use - that is, may this act as either 
> convertFormat or copy?  C11 F.6 clearly envisages that such a return 
> statement may do a conversion to the same type in the case of wider 
> evaluation formats.  But 6.8.6.4#3 only refers to conversions "If the 
> expression has a type different from the return type of the function in 
> which it appears".
> 
> -- 
> Joseph S. Myers
> joseph at codesourcery.com