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    <p>Your immediate problem is that you try to pass a temporary <code>streamAggrator</code> object to a function which takes a <code>streamAggrator</code> by non-<code>const</code> reference. You can't bind temporary object to non-<code>const</code> references. The work-around for this problem is to make the output operator member of your <code>streamAggrator</code>: while you cannot bind a temporary to a non-<code>const</code> reference, you <em>can</em> call non-<code>const</code> member functions. Note that you'll also get problems with maniputors like <code>std::flush</code> (the issue there is that these are templates themselves and you actually need to a concrete operator to call them with to have the compiler deduce their template arguments).</p> <p>Clearly, I would solve the problem properly, i.e., instead of trying to dig about an attempt to a solution which doesn't create a stream, I would create a <code>std::streambuf</code> do do the actual work. Your examples doesn't do anything useful, i.e., I can't really tell what you are trying to do but the code looks remarkably like trying to do something like <code>teestream</code>: write once but send the output to multiple destintations. I have posted corresponding stream buffers quite a few times in the post (mostly on Usenet, though, but I think, at least, once on Stackoverflow, too).</p> <p>Although I don't know how to get rid of the macro to fill in the <code>__FILE__</code> and the <code>__LINE__</code>, the actual stream formatting should probably use a stream buffer:</p> <pre><code>struct teebuf: std::streambuf { private: std::streambuf* sb1; std::streambuf* sb2; public: teebuf(std::streambuf* sb1, std::streambuf* sb2): sb1(sb1), sb2(sb2) {} int overflow(int c) { this-&gt;sb1-&gt;sputc(c); this-&gt;sb2-&gt;sputc(c); return std::char_traits&lt;char&gt;::not_eof(c); } int sync() { this-&gt;sb1-&gt;pubsync(); this-&gt;sb2-&gt;pubsync(); } }; class logstream : std::ostream { std::ofstream out; teebuf sbuf; public: logstream() : out("file.log") , sbuf(out.rdbuf(), std::clog.rdbuf()) { this-&gt;init(&amp;this-&gt;sbuf); } logstream(logstream&amp;&amp; other) : out(std::move(other.out)) , sbuf(std::move(other.sbuf)) { this-&gt;init(&amp;this-&gt;sbuf); }; </code></pre> <p>I <em>think</em> you can return the log stream. I don't know what your logging level is meant to do but I guess its processing was removed while preparing the question: it is probably necessary to change the implementation to take the logging level suitably into account.</p>
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    1. USDietmar Kühl
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    1. COThx, "You can't bind temporary object to non-const references" - What's the reason behind it?
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    2. COand you're right about the usage
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    3. CO@GuyL: In general, something is add if you try to change temporaries. The reasoning is explained, e.g., in Bjarne's "Design and Evolution of C++". I don't really buy into entirely and think that `const` was an early attempt at what is properly addressed with rvalue references. Since you have tagged your question C++11 I'll post a sketch of how I would do it (it requires some C++11 functionality, though, to return streams).
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