Re: POSIX and float rounding

[Guy Harris <gharris () sonic net>]

On Mar 19, 2026, at 4:52 PM, Denis Ovsienko <denis () ovsienko info> wrote:

> Are you saying that fesetround() cannot solve this problem reliably?

It could solve it reliably *if* you choose a rounding mode *other* than round-to-nearest; I don't think the other modes 
have the problem of "which of 0 and 1 is nearest to .5?"

Unfortunately, fesetround(), prior to C23, doesn't offer a way to tell the floating-point environment how to break the 
tie, as it offers no choice between different flavors of round-to-nearest. C23 distinguishes between FE_TONEAREST, 
which is specified as being roundTiesToEven, and an *optional* FE_TONEARESTFROMZERO, which is specified as 
roundTiesToAway.
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