[cfe-users] Is there a way to make clang warn on this code?

Jordan Rose jordan_rose at apple.com
Mon Mar 17 09:40:46 PDT 2014

On Mar 15, 2014, at 19:01 , David Blaikie <dblaikie at gmail.com> wrote:

> On Fri, Mar 14, 2014 at 7:05 PM, Richard Trieu <rtrieu at google.com> wrote:
>> Quentin,
>> Clang does not have a warning for uninitialized fields in class methods.
>> I've looked before to add a warning to flag any unused fields at the end of
>> the a constructor.  However, there were good reasons to have uninitialized
>> fields, such as having an Init() method later that initializes the fields,
>> or a guard variable to protect against uninitialized use.  Also,
>> -Wuninitialized typically warns on the use of an uninitialized variable, not
>> the mere presence of one.
>> The other idea is to do cross method analysis, either using the control flow
>> of a program to determine which methods are used in which order, or testing
>> methods against constructors.  Such an analysis would likely be too
>> expensive, and would be more suited for static analysis.
> We already have at least one cross-method analysis which could
> actually be used as the basis for the warning under discussion here:
> -Wunused-member-variable. This warning only fires if there are no
> friends and a private member in a situation where all member functions
> are defined in one translation unit.  So we could use this to show
> that there's no initialization of the variable anywhere, but there are
> uses of it. (essentially the same as -Wunused-member-variable, except
> allow reads as well)

The analyzer also catches the particular case in your stripped-down test file, and should do so on real code as long as it's all visible in one translation unit. It'd be a lot harder to make this a cross-TU analysis, of course.

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