Boost C++ Libraries: Ticket #8405: VC++ 2012 compiler warning C4189: '...' : local variable is initialized but not referenced

type, severity changed

Barend Gehrels — Fri, 05 Apr 2013 20:55:54 GMT

type Bugs → Support Requests
severity Problem → Not Applicable

The code is:

int const n = int(section.range_count); return boost::is_same

<

typename tag_cast

<

typename geometry::point_type<Geometry1>::type, areal_tag

::type,

areal_tag

::value

&& index1 == 0 && index2 >= n - 2

;

As you can see the variable n is referenced.

However, if is_same returns false, the variable is (at compiletime) indeed not referenced.

This can be solved by using another (and more complex) construction, not by just removing n.

This has currently no priority.

The advice is to check with /W3.

The same for fp_strategy, this strategy is used, be it sometimes only the static functions, but that is not known at that specific location.

I change the classification from "Bug" to "Support Request"

severity changed

Barend Gehrels — Fri, 05 Apr 2013 21:13:07 GMT

severity Not Applicable → Cosmetic

Sat, 06 Apr 2013 15:26:08 GMT

Thank you for looking into this. I have no issue with the code as it is. However, I do have an issue with the warning being triggered. If you know that the warning is triggered even though the code is fine, why not locally suppress the warning with #pragma warning(disable:4189)?

Compiling with /W3 is not an option for me; I will continue to suppress this warning specifically for boost::geometry. That's not a practical problem, I just think suppressing it locally in your code, with an appropriate comment, would be a better solution.

Barend Gehrels — Sat, 06 Apr 2013 18:51:41 GMT

Yes, disabling might be an option. However, we get the chance then that gcc or clang still complain (did not check).

Another option is adding boost::ignore_unused_variable_warning(n); that is quite easy to do ;-) This is valid for all compilers, and is not taking runtime. I did that earlier for some strategies, so it can also be done for fp_strategy.

This might be done for most (but probably not all) your reported warning problems.

milestone changed

Barend Gehrels — Sat, 06 Apr 2013 18:52:48 GMT

milestone To Be Determined → Boost 1.54.0

status changed; resolution set

Barend Gehrels — Sat, 06 Apr 2013 21:35:01 GMT

status new → closed
resolution → fixed