[cfe-dev] error: unknown argument: '-ffoo' => reason ?

[Rafael Espíndola]

>> At least all the ones that just enable or disable a pass. Things like
>> -malign-double would probably turn a build error into a miscompilation
>> if ignored, so probably not.
>
> I disagree that we should be adding random "disable pass" options. It
> just doesn't make sense and most of them shouldn't have been applied
> unconditionally in first place as they are workarounds for optimizer
> bugs in specific gcc versions. From the list:
> -  -fexcess-precision must not be dropped silently,
> -  -fno-check-new / -fcheck-new was discussed before, language lawyers
>    can comment
> -  -finput-charset=UTF-8 would be safe to drop as it is the default
> -  -fsingle-precision-constant potentially changes behavior
> -  -fno-defer-pop was typically used without good reason, but custom asm
>    parsers might depend on it, so no.
> -  -z should likely be fixed to be -Wl,-z
>
> I would not change anything except maybe -finput-charset=UTF-8.

I think we are talking about different things. Yes, at some point it
would be nice to have a rationale for every option clang supports or
doesn't.  My point is just that given that it warned on all of those
(including ABI breaking ones) no long ago, it seems reasonable to
going back to warning on an explicit list and then work our way over
that list.

Cheers,
Rafael