GCC 12 emits `-Wuninitialized` warnings

[jngrad]

The GCC -Wmaybe-uninitialized warning reported in #27 was silenced by a diagnostic pragma in #38, however in GCC 12 the warning has become -Wuninitialized. Reproducible on Fedora with gcc-c++-12.0.1-0.16.fc36 and gcc-c++-12.1.1-1.fc37. Probably relevant part of the GCC 12 changelog: Eliminating uninitialized variables.

MWE:

#include <boost/test/unit_test.hpp>

struct my_precondition {
  boost::test_tools::assertion_result operator()(boost::unit_test::test_unit_id) {
    return false;
  }
};

BOOST_TEST_DECORATOR(*boost::unit_test::precondition(my_precondition()))
BOOST_AUTO_TEST_CASE(my_test) {
}

Output (live example):

$ g++ -Wall -O3 -c mwe.cpp
In file included from /usr/include/boost/function/detail/maybe_include.hpp:22,
                 from /usr/include/boost/function/function1.hpp:11,
                 from /usr/include/boost/test/tree/decorator.hpp:30,
                 from /usr/include/boost/test/tools/fpc_tolerance.hpp:19,
                 from /usr/include/boost/test/tools/fpc_op.hpp:19,
                 from /usr/include/boost/test/test_tools.hpp:54,
                 from /usr/include/boost/test/unit_test.hpp:18,
                 from mwe.cpp:1:
In member function ‘void boost::function1<R, T1>::assign_to_own(const boost::function1<R, T1>&) [with R = boost::test_tools::assertion_result; T0 = long unsigned int]’,
    inlined from ‘boost::function1<R, T1>::function1(const boost::function1<R, T1>&) [with R = boost::test_tools::assertion_result; T0 = long unsigned int]’ at /usr/include/boost/function/function_template.hpp:746:26,
    inlined from ‘boost::function<R(T0)>::function(const self_type&) [with R = boost::test_tools::assertion_result; T0 = long unsigned int]’ at /usr/include/boost/function/function_template.hpp:1105:76,
    inlined from ‘boost::unit_test::decorator::precondition::precondition(predicate_t)’ at /usr/include/boost/test/tree/decorator.hpp:280:61,
    inlined from ‘void __static_initialization_and_destruction_0(int, int)’ at mwe.cpp:9:1,
    inlined from ‘(static initializers for mwe.cpp)’ at mwe.cpp:11:1:
/usr/include/boost/function/function_template.hpp:910:22: warning: ‘*(unsigned char (*)[24])((char*)&<unnamed> + offsetof(boost::predicate_t, boost::function<boost::test_tools::assertion_result(long unsigned int)>::<unnamed>.boost::function1<boost::test_tools::assertion_result, long unsigned int>::<unnamed>.boost::function_base::functor))’ is used uninitialized [-Wuninitialized]
  910 |           std::memcpy(this->functor.data, f.functor.data, sizeof(boost::detail::function::function_buffer));
      |           ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/boost/test/unit_test.hpp:19:
mwe.cpp: In function ‘(static initializers for mwe.cpp)’:
mwe.cpp:9:71: note: ‘<anonymous>’ declared here
    9 | BOOST_TEST_DECORATOR(*boost::unit_test::precondition(my_precondition()))
      |                                                                       ^

[pdimov]

Fixed by a variation of #43.

[jngrad]

Fixed by 5b4e279.