Uninitialized warning with gcc 16.1.0

[J-Richter]

With boost 1.91.0 and GCC 16.1.0 I get this warnings for our code. I shortened the template arguments to make it more readable. Might also be a compiler bug.

In member function 'boost::multi_index::multi_index_container<>::final_node_type* boost::multi_index::multi_index_container<>::header() const',
inlined from 'boost::multi_index::detail::index_base<>::final_node_type* boost::multi_index::detail::index_base<>::final_header() const' at boost/multi_index/detail/index_base.hpp:215:61,
inlined from 'boost::multi_index::detail::hashed_index<>::index_node_type* boost::multi_index::detail::hashed_index<>::header() const at boost/multi_index/hashed_index.hpp:1272:59,
inlined from 'boost::multi_index::detail::hashed_index<>::hashed_index(const ctor_args_list&, const allocator_type&) at boost/multi_index/hashed_index.hpp:743:5:
boost/multi_index_container.hpp:554:26: warning: '((const boost::multi_index::multi_index_container<>*)this)[230584300921369395].boost::multi_index::multi_index_container<>::boost::multi_index::detail::header_holder<>.boost::multi_index::detail::header_holder<>::member' is used uninitialized [-Wuninitialized]
554 |     return &*bfm_header::member;

[joaquintides]

Yes, the following

multi_index/include/boost/multi_index_container.hpp

Line 554 in 179b5de

return &*bfm_header::member;

is technically UB when bfm_header::member hasn't been initialized. Would you mind replacing the offending line with

  return boost::addressof(bfm_header::member); 

and checking whether you have additional warnings? I'll fix this in time for Boost 1.92 (Aug 2026). Thank you!

[joaquintides]

Would you mind replacing the offending line with [boost::addressof].

Strike that, the problem is a little more complex. Investigating.

[joaquintides]

Hi Jörg, could you verify if #97 solves the issue on your end? Thank you!

[J-Richter]

Hi, the warnings are gone and our tests are also successful!

[joaquintides]

Awesome. Thanks for the report!