"Boespflug, Mathieu" <m...@tweag.io> writes: > Hi Ben, > > could we enlarge the options a bit? I feel that we're in a false > dichotomy currently. I think the issue isn't so much what warnings you > see from the compiler with common settings, so much as "what warnings > will cause my build to fail?". i.e. the issue isn't what's in -Wall, > it's what goes in -Werror...
I can certainly see this point. As pointed out by Herbert, this is best provided by #11219 which unfortunately didn't make the 8.0 release. > If we don't include -Wcompat in -Wall, then I suspect Ben is quite > right that many will ignore / not be aware of -Wcompat hence rendering > the 3 release policy rather moot (it's much less useful if developers > don't /know/ they're incompatible until the last minute). If we do > include it then packages with -Wall -Werror will fail far too early: > i.e. way before the compat change actually happens, 3 compiler > releases down the line. So may I suggest the following: > > * include -Wcompat and -Wall, but make it "magic" so that -Wcompat > never causes a build to fail even when users set -Wall -Werror. > > This should address the concerns I've been hearing by folks at large > companies who say that at their company a warning is equivalent to an > error, because they always compile with -Wall -Werror. Otherwise > warnings just accumulate, hence no one pays attention to them, hence > warnings become useless. > > As an aside: I believe -Wall should do what it says on the tin: enable > all warnings. I am sympathetic to this argument. For better or for worse, however, there seems to be precedent for excluding some warnings in -Wall. Clang, for instance, uses -Weverything for "give me everything". Up until this point we have followed this model (although don't have a -Weverything); for instance, we disable -Wimplicit-prelude in -Wall since it is inappropriate for most users. I'm not sure whether we should break with this tradition as users are quite used to invoking their compiler with `-Wall` during development. Throwing warnings about implicit Prelude imports at them would be surprising to say the least. > When GHC comes up with new warnings, we should pretty > much never hesitate to add them to the -Wall set. I agree. This is why Simon wrote an explicit declaration that -Wall is not stable to the list a few weeks ago. We really don't want to worry about breaking builds of (potentially broken) user code when adding warnings. Cheers, - Ben
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