[boost] [thread] Why the at_thread_exit cleanup function be const?

Subject: [boost] [thread] Why the at_thread_exit cleanup function be const?
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2008-11-10 11:37:09

In addition, if a remove the const on operator()() 
    struct mycallable1
    {
        void operator()()  {
            std::cout << "mycallable1" << std::endl;
        };
    };

    void my_thread() {
        std::cout << "my_thread" << std::endl;
        mycallable1 x;
        boost::this_thread::at_thread_exit(x);
    }

I get the following error:

gcc.compile.c++ ..\..\..\bin.v2\libs\interthreads\test\hello_world.test\gcc-4.3.2\debug\target-os-cygwin\threadapi-pthread\threading-multi\hello_world.o
../../../boost/thread/detail/thread.hpp: In member function `void boost::detail::thread_exit_function<F>::operator()() const [with F = mycallable1]':
..\example\hello_world.cpp:52:   instantiated from here
../../../boost/thread/detail/thread.hpp:474: error: passing `const mycallable1' as `this' argument of `void mycallable1::operator()()' discards qualifiers

Why the cleanup function must be const?

Best,

Vicente

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