[cfe-commits] Support <x>-to-bool warnings for more contexts

[John McCall]

On Apr 3, 2012, at 9:42 AM, Matt Beaumont-Gay wrote:
> On Mon, Apr 2, 2012 at 18:03, David Blaikie <dblaikie at gmail.com> wrote:
>> Another thing I noticed as I was exploring this. We have a warning for
>> float-literal-to-int such as:
>> 
>> conv.cpp:2:9: warning: implicit conversion turns literal
>> floating-point number into integer: 'double' to 'int'
>> [-Wliteral-conversion]
>> int i = 3.1415;
>>    ~   ^~~~~~
>> 
>> But this warning is off-by-default. Why is that?
> 
> Historical accident? I didn't even remember that it was off by
> default. I say flip the switch to turn it on.
> 
>> It's already
>> relatively conservative (allowing things like : "int i = 3.0" because
>> 3.0 converts to an int without loss of precision) - though it's not a
>> DiagnoseRuntimeBehavior, which it could be changed to (to be
>> consistent with similar things for integers like "unsigned char c =
>> 256").
>> 
>> Or is it really that common to deliberately use floating point
>> literals to initialize integer values?
> 
> Well, the "int kNumMicrosPerSecond = 1e6" case is very common, but the
> warning is suppressed in that case. (Actually, that may be one reason
> the warning is off by default -- the first implementation didn't have
> such suppression.)

I believe that's correct.

I don't mind turning this on by default for literals with fractional precision.
We're a bit close to the release, but we should get acceptable qualification
in the next week or so.

John.