has_*_operator.hpp generates C6334 using VC++

[ianjirka@…]

Warning 2 warning C6334: sizeof operator applied to an expression with an operator might yield unexpected results: Parentheses can be used to disambiguate certain usages. c:\users\ian\dev\tensor\main\code\external\boost\latest\boost\type_traits\detail\has_binary_operator.hpp

This can be fixed by adding an extra set of parentheses around returns_void( ... ). For example: sizeof((returns_void(...))

For example: has_binary_operator.hpp:95 Was:

BOOST_STATIC_CONSTANT( bool, value = (sizeof(::boost::type_traits::yes_type) == sizeof( returns_void( (make<Lhs>() BOOST_TT_TRAIT_OP make<Rhs>(), returns_void_t()) ))) );

With fix:

BOOST_STATIC_CONSTANT( bool, value = (sizeof(::boost::type_traits::yes_type) == sizeof((returns_void( (make<Lhs>() BOOST_TT_TRAIT_OP make<Rhs>(), returns_void_t()) )))) );

I was able to fix has_binary_operator.hpp and has_prefix_operator.hpp this way. I'm sure other metafunctions are affected as well.

[John Maddock]

Apologies for taking such a long time to get to this... but do you have a test case?

We compile our tests with -W4 _Werror and they don't show this warning.

Many thanks.

[anonymous]

C6334 is a code analyser warning rather than a regular compiler warning, so you need a version of the compiler that supports the analyser to get it.

[anonymous]

Understood, can you submit either a patch or a pull request - as I can't reproduce here it is probably safer if you check the proposed fix works?

[John Maddock]

Finally fixed in ​https://github.com/boostorg/type_traits/commit/e31d0ab7bdddd08b39342afbf9be3d4ade21d8cf (develop only)