<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Sep 24, 2014, at 4:54 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" class="">dblaikie@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><br class=""><div class="gmail_extra"><br class=""><div class="gmail_quote">On Wed, Sep 24, 2014 at 4:42 PM, Argyrios Kyrtzidis <span dir="ltr" class=""><<a href="mailto:kyrtzidis@apple.com" target="_blank" class="">kyrtzidis@apple.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><div class="">This isn’t a style checker, this is to make sure you are not overriding something by accident.</div></div></blockquote><div class=""><br class=""></div><div class="">For context, I took those quotations from a thread about a warning for "using a null pointer other than nullptr" which seems pretty analogous to this warning. "Use this feature because it might help you find bugs" but I think Doug was basically saying that the guideline to use a particular feature is a stylistic one, even if that style then leads to finding bugs.</div></div></div></div></div></blockquote><div><br class=""></div><div>Yeah, both warnings fall into the “introduce extra syntax, the consistent use of which will prevent bugs” camp. One can choose to use the feature if the syntactic overhead is less burdensome than tracking down the bugs, or not. </div><div><br class=""></div><div>My position has softened somewhat, and I don’t feel as strongly that these warnings is “purely stylistic”. I still think an off-by-default warning is extremely unfortunate, because new warning flags aren’t that discoverable. I’d feel a lot better if some part of the warning could be on by default. For example, if you’ve uttered “override” at least once in a class, it makes sense to warn-by-default about any other overrides in that class that weren’t marked as “override”, because you’re being locally inconsistent. Or maybe you can expand that heuristic out to a file-level granularity (which matches better for the null point constant warning) and still be on-by-default. Explicitly providing the warning flag (or some other related warning flag) could turn the warning on everywhere, for those who want the rule consistently applied to their code base.</div><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span>- Doug</div><div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class=""><div class=""><br class=""></div><div class="">It needs to be off-by-default due to the vast amount of C++ code that exists out there, but we can have it enabled when you create a new project.</div><div class=""><div class="h5"><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Sep 24, 2014, at 4:16 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" target="_blank" class="">dblaikie@gmail.com</a>> wrote:</div><br class=""><div class=""><div dir="ltr" class=""><br class=""><div class="gmail_extra"><br class=""><div class="gmail_quote">On Wed, Sep 24, 2014 at 3:57 PM, jahanian <span dir="ltr" class=""><<a href="mailto:fjahanian@apple.com" target="_blank" class="">fjahanian@apple.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">Hi all,<br class="">
<br class="">
We have an enhancement request from our users to provide<br class="">
warning if ‘override’ control is missing. This warning is off by default as it will<br class="">
be noisy (but it will show itself with -Weverything).<br class="">
Is such a patch useful enough to go into the trunk? Also, comment on the patch is appreciated.<br class="">
I will provide ‘fixit’ later if this is a worthwhile patch.<br class=""></blockquote><div class=""><br class=""></div><div class="">While I rather like the idea of such a warning, the usual bar has been a strong aversion to adding off-by-default warnings. I think the theoretical future might be building warnings like this into clang-tidy, then providing some plugin-like option to enable certain clang-tidy warnings in your normal builds.<br class=""><br class="">(because I was curious, I went back & found some choice quotes from Doug Gregor on warnings like this (this is what he told me, years ago, when I proposed adding a warning for null pointers that aren't nullptr*):<br class=""><br class=""><div class=""><div class=""><font face="arial, helvetica, sans-serif" class=""><span class="">"Off</span>-by-<span class="">default</span> <span class="">warnings</span> are not a mechanism to subvert our normal processes for vetting a<span class="">warning</span>. In general, we should avoid <span class="">off</span>-by-<span class="">default</span> <span class="">warnings</span>: if it's not good enough to turn on by <span class="">default</span>, why do we have it at all? The vast majority of users will never see an <span class="">off</span>-by-<span class="">default</span> <span class="">warning</span>."</font></div><div class=""><font face="arial, helvetica, sans-serif" class="">"A compiler is not a style checker, nor should it ever be."</font></div></div><div class=""><font face="arial, helvetica, sans-serif" class=""><span class="">"Warnings</span> are intended to find potential problems in the source code. Style migration is the domain of separate tools.")<br class=""><br class="">(& cc'ing Doug in case there's something about this that's different/things have changed over the years)</font></div><br class="">* today, I'd probably be able to get that in on the basis of compatibility with GCC's <span style="font-family:monospace;font-size:inherit" class="">-Wzero-as-null-pointer-constant</span></div><div class=""> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br class="">
- Fariborz<br class="">
<br class="">
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