Fix Werror=sign-compare

[stephanlachnit]

On GCC with -Werror=sign-compare, using atomic_queue gives the following error:

../subprojects/atomic_queue-1.6.6/include/atomic_queue/atomic_queue.h:337:27: error: comparison of integer expressions of different signedness: ‘unsigned int’ and ‘int’ [-Werror=sign-compare]
  337 |         return was_size() >= static_cast<int>(static_cast<Derived const&>(*this).size_);
      |                ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I don't see any good reason why the size should be cast to an integer. In fact, the second expression is just the capacity anyway, so let's use the capacity instead. Then both expressions use unsigned for a well defined comparison.

[max0x7ba]

On GCC with -Werror=sign-compare, using atomic_queue gives the following error:

../subprojects/atomic_queue-1.6.6/include/atomic_queue/atomic_queue.h:337:27: error: comparison of integer expressions of different signedness: ‘unsigned int’ and ‘int’ [-Werror=sign-compare]
  337 |         return was_size() >= static_cast<int>(static_cast<Derived const&>(*this).size_);
      |                ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I don't see any good reason why the size should be cast to an integer. In fact, the second expression is just the capacity anyway, so let's use the capacity instead. Then both expressions use unsigned for a well defined comparison.

You are right.

This is a remnant of an original expression where the left signed term got replaced with unsigned was_size().

[max0x7ba]

This change is available in tag https://github.com/max0x7ba/atomic_queue/releases/tag/v1.6.7