void container parameters not ignored with BOOST_INTRUSIVE_VARIADIC_TEMPLATES

[Matei David <matei@…>]

When BOOST_INTRUSIVE_VARIADIC_TEMPLATES is used, void template parameters used to construct intrusive containers are not properly ignored, and instead cause compilation failure. E.g., list< A, void > l does not compile, but it compiles ok when that symbol is not defined.

As one consequence, the library test suite cannot be compiled with that symbol defined, because tree-based containers in the test suite are built with void parameters.

Technically, the issue rests with the do_pack struct in pack_options.hpp. In non-variadic context, voids are properly ignored. In the (heavy TMP) variadic context, they aren't.

[Ion Gaztañaga]

Using void parameters is not allowed, as the user must pass only allowed options. The documented interface is a variadic options interface. In C++03 compilers it's implemented with default template arguments to avoid but it's an implementation detail .