Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is an older version of Boost and was released in 2024. The current version is 1.89.0.

http::message::operator= (2 of 2 overloads)

Assignment.

message&
operator=(
    message const&);