Reconsidering -Wall and -Wcompat

Ben Gamari ben at
Mon Feb 15 11:00:04 UTC 2016

Joachim Breitner <mail at> writes:

> [Deliberately restricting my reply to one mailing list. Cross-posting
> is usually not required.]
> Hi,
> Am Sonntag, den 14.02.2016, 19:51 +0100 schrieb Sven Panne:
>> As stated on the Wiki, stuff in -Wcompat will often be non-
>> actionable,
> you omitted the important “if backwards compatibility is desired;”. The
> sometimes complicated hoops that you will have to jump through to gain
> 3-release-backward-compatibility are not something I expect every
> developer to follow, and for most others, “adjust early to API changes”
> will more likely be the sensible thing to do. Those might want to leave
> -Wcompat in their builds.
Couldn't have said it better myself. Ubiquitous usage of -Wall isn't a
problem; it's when users begin to assume that the behavior of -Wall
(which nominally includes *all* warnings supported by GHC) will remain
stable across releases that the trouble begins.


- Ben
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