[llvm-commits] [LLVMbugs] [Bug 7322] ms vcpp build warnings

[nate begeman]

Sure, sorry, I seemed to recall shifts implicitly promoting to int, but maybe that's in C and not C++, will cast.

Nate

On Jun 15, 2010, at 12:05 PM, Chris Lattner wrote:

> Nate, can you change these to use "nElts << (int)quad" or something?
> 
> -Chris
> 
> On Jun 15, 2010, at 7:43 AM, Dimitry Andric wrote:
> 
>> On 2010-06-14 22:39, bugzilla-daemon at llvm.org wrote:
>>> --- Comment #1 from Chris Lattner <clattner at apple.com> 2010-06-14 15:39:27 CDT ---
>>> there are a bunch of build warnings with MSVC.  If you're interested in helping
>>> with this, please send patches to llvm-commits, thanks!
>> 
>> What I see quite often with VC++ is this warning:
>> 
>> .\NeonEmitter.cpp(529) : warning C4804: '<<' : unsafe use of type 'bool' in operation
>> 
>> which comes from bool variables used as shift count, e.g:
>> 
>> bool dummy, quad = false;
>> ...
>>   b = Duplicate(nElts << quad, typestr, "b");
>> 
>> I'm not sure if this is unnecessarily paranoid of VC++, as the standard
>> seems to imply it should be no problem, if I read it correctly:
>> 
>> [conv.prom]
>> 4. An rvalue of type bool can be converted to an rvalue of type int,
>>  with false becoming zero and true becoming one.
>> 
>> and [conv.integral]:
>> 
>> 4. If the destination type is bool, see 4.12. If the source type is
>>  bool, the value false is converted to zero and the value true is
>>  converted to one.
>> 
>> In short, is it worthwhile to appease VC++ here, by using an int or
>> unsigned instead, or should we just stash in a pragma to disable this
>> particular warning?
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>