`static` global functions in headers interferes with use of modules

[davidstone]

Beast has some global functions in its headers (for instance, clamp in boost/beast/core/detail/clamp.hpp) that are declared static. static global functions are inaccessible to the second phase of name lookup in templates instantiated outside of the module. So for instance, if I have a module like

module;

#include <boost/beast.hpp>
#include <string_view>

export module thingy;

struct Thingy {
    void f(std::string_view text, auto function) {
        m_socket.async_write(boost::asio::buffer(text), function);
    }
private:
    boost::beast::websocket::stream<boost::asio::ip::tcp::socket> m_socket;
};

If a user attempts to call Thingy::f, they will get an error message like

boost/beast/websocket/impl/write.hpp:238:35: fatal error: no matching function for call to 'clamp'
  238 |             bytes_transferred_ += clamp(fh_.len);

This is because the clamp overloads are declared static (in the "translation-unit local" sense).

Removing static would fix this problem. clamp is a set of function templates so it doesn't need any other change. I'm not sure if there are other functions that have a similar issue, but that's the only one I've run into so far.

[vinniefalco]

LOL should have just submitted a pull request. This looks like a typo and thank you for finding it :)