[cfe-commits] [Patch] Checker for assignment of non-Boolean value to Boolean variable

[Anna Zaks]

On Dec 8, 2011, at 6:23 PM, David Blaikie wrote:

> On Thu, Dec 8, 2011 at 6:03 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
>> On Wed, Dec 7, 2011 at 5:53 PM, Ryan Govostes <rzg at apple.com> wrote:
>>> Hello,
>>> 
>>> Please find attached a new checker for the static analyzer that warns on the assignment of a non-Boolean value to a variable with a Boolean data type. It supports Boolean data types defined by C++, C99, and Objective-C as well as those in stdbool.h and MacTypes.h.
>> 
>> Some related work:
>> 
>> http://blog.mozilla.com/mwu/2011/07/28/the-twelve-booleans-of-mozilla/
> 
> Awesome.
> 
> Yeah - now I understand the problem, I wonder again if this could be
> implemented (in a simpler but more strict manner) as a front-end
> warning in the same way that null-conversions are warned about (though
> it'd have to be a bit smarter - perhaps detecting the macro/typedef
> that was used to declare a variable or assign a constant to it - not
> to mention that the current Clang null-conversion support is broken
> (I've another thread pending some discussion on that)). But in general
> this should be good for any >2 state value masquerading as an int -
> for C++ bool or anything that's as good as it, a lesser warning (if
> any at all) might be appropriate.
> 

My understanding is that you are suggesting to add a compiler warning when a constant, which is not 0 nor 1, is being assigned to a boolean variable. Such warning would be weaker then this checker, so the checker should still go in. 

Cheers,
Anna.

> The usual warning with Win32 BOOL is to never mix BOOL & bool - but
> with this kind of warning/checking you could be confident that BOOL is
> only 0 or 1 and so "someBOOL == some_bool" would work sensibly (&
> never be "2 == 1" => false, for example)
> 
> - David
> 
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