FE_DOWNWARD, FE_UPWARD and FE_TOWARDZERO are not defined

[saghul]

Hey there! I'm having quite some fun with WASI, kudos for the nice work!

Today while porting a library (QuickJS specifically) I ran into this. As the title says, those are not defined in wasi-sdk/share/sysroot/include/bits/fenv.h. I manually defined them and compilation continued though :-)

[sunfishcode]

Thanks! WebAssembly itself only supports round-to-nearest. It doesn't support any other rounding modes. To reflect this, WASI libc only defines FE_TONEAREST, and not FE_DOWNWARD, FE_UPWARD and FE_TOWARDZERO.

You're welcome to manually define them, although note that this won't enable the platform to respect these rounding modes, so you may see floating-point results with incorrect rounding.

[saghul]

Ah, this is good to know! Do you see the other modes ever making it to the spec?

[sunfishcode]

It's possible. There are some ideas about how this might work sketched out here, though at this time there isn't yet an active proposal for them, so it's difficult to say when this might advance.

[saghul]

Thanks for the insight! Feel free to close this if appropriate. Cheers!