[cfe-commits] r140574 - in /cfe/trunk: include/clang/Basic/DiagnosticGroups.td include/clang/Basic/DiagnosticSemaKinds.td test/SemaCXX/warn-literal-conversion.cpp test/SemaCXX/warn-string-conversion.cpp

Matt Beaumont-Gay matthewbg at google.com
Thu Sep 29 01:19:12 CDT 2011

On Wed, Sep 28, 2011 at 22:52, John McCall <rjmccall at apple.com> wrote:
> On Sep 28, 2011, at 10:25 PM, Matt Beaumont-Gay wrote:
>> On Wed, Sep 28, 2011 at 11:47, John McCall <rjmccall at apple.com> wrote:
>>> On Sep 26, 2011, at 6:10 PM, Chandler Carruth wrote:
>>> On Mon, Sep 26, 2011 at 4:39 PM, John McCall <rjmccall at apple.com> wrote:
>>>>> The string literal to boolean conversion is a new warning.  There was
>>>>> some discussion of where to put it, from literal-conversion or
>>>>> bool-conversion.  I was moving it to its own flag so we can have the
>>>>> warning while we figure out which of these places would be best for
>>>>> it.
>>>> Okay, as long as it doesn't stay there.  And for next time, it's fine to just let it sit in one or the other until the discussion is done, I think.
>>> This was largely my request to Richard. Essentially, -Wliteral-conversion fires a great deal, with a high false-positive rate. We're considering turning it on anyways, but I can imagine a lot of code may never be interested in turning that set of warnings on.
>>> However, -Wbool-conversion and this new warning Richard added were based on specific bug reports. We've found hundreds of bugs with these two warnings, and very few false-positives. I originally suggested just putting both of these under 'bool-conversion' even though one is converting from a bool to a pointer, and the other from a pointer to a bool. I would be happy with consolidating them into any flag name that seems appropriate and sufficiently descriptive. My only real goal is to keep the extremely high-value warnings available even when -Wliteral-conversion (much less the even more noisy variants) aren't feasible for a codebase.
>>> So let me turn this around.  False-to-pointer and string-literal-to-bool conversions are both clearly under the rubric of -Wliteral-conversion.  I can understand not wanting to turn on a category with massive false positives, but, well, massive false positives are a fixable problem.  Why don't we just put the noisy cases into their own categories, not part of -Wliteral-conversion, and then move them back in if/when we fix their problems?
> Your quoting style is broken;  please use something that divides responses properly.

Sorry, I think that's a recent Gmail bug.

>> The noisy warning in question is floating-point-literal-to-int, which
>> fires on a lot of code like "int kNumMicrosPerSecond = 1e6;". How
>> would you feel about moving that warning under a more specific flag?
>> And, to get slightly off-topic, how would you feel about adding code
>> to that warning to silence it in "safe" cases for literals written in
>> exponential form?
> I think we should definitely not be warning for conversions that
> preserve values exactly.

I'd still like to warn on "int i = 1.0", since we can offer a fixit
hint that is always a strict (if minor) improvement.


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