Re: [boost] BOOST_STATIC_ASSERT question

From: Vesa Karvonen (vesa.karvonen_at_[hidden])
Date: 2001-05-25 01:55:18

From: "Greg Chicares" <chicares_at_[hidden]>
>   // alternative enum based implementation:
>   #define BOOST_STATIC_ASSERT( B ) \
>      enum { BOOST_ASSERT_JOIN(boost_static_assert_enum_, __LINE__) \
> -       = sizeof(::boost::STATIC_ASSERTION_FAILURE< ( B ) >) }
> +       = sizeof(::boost::STATIC_ASSERTION_FAILURE< ( !!B ) >) }
                                                      ^^^^^^^
>   #endif

The above form is dangerous. The macro parameter should be in parens:

  +       = sizeof(::boost::STATIC_ASSERTION_FAILURE< !!( B ) >) }
                                                      ^^^^^^^
Consider the following code:

    BOOST_STATIC_ASSERT(2 == 2);

Which would expand to:

enum { boost_static_assert_enum___LINE__
       = sizeof(::boost::STATIC_ASSERTION_FAILURE< ( !!2 == 2 ) >) }