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POMacro to replace C++ operator new
 

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    <p>Is it possible to create macros to replace all forms of <code>operator new</code> with overloads that include additional args...say <code>__FILE__</code> and <code>__LINE__</code>?</p> <p>The trouble appears to be that <code>operator new</code> can either be coded with or without parentheses, therefore:</p> <ul> <li><p><em>object-like</em> macros:</p> <pre><code>#define new new(__FILE__, __LINE__) </code></pre> <p>will replace declarations like:</p> <pre><code>A* a = new A(); </code></pre></li> <li><p>and <em>function-like</em> macros:</p> <pre><code>#define new(A) new (A, __FILE__, __LINE__) </code></pre> <p>will replace declarations like:</p> <pre><code>A* a = new(std::nothrow) A(); </code></pre></li> </ul> <p>Unfortunately it's an error to attempt to declare two macros with the same <em>identifier</em>, even if they are of different <em>types</em>, so the following fails:</p> <pre><code>#define new new(__FILE__, __LINE__) #define new(A) new (A, __FILE__, __LINE__) // Error: "new" already defined </code></pre> <p>Since I'm using g++ I was hopeful that employing their syntax of <a href="https://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/gcc/variadic-macros.html" rel="nofollow noreferrer">variadic macros</a> would yield success, but unfortunately not. The following:</p> <pre><code>#define new(...) new(__FILE__, __LINE__, ## __VA_ARGS__) </code></pre> <p>only matches <code>new(xyx) A()</code>, not <code>new A()</code>.</p> <p>I know that <a href="http://web.archive.org/web/20090513070647/http://www.scs.cs.nyu.edu/~dm/c++-new.html" rel="nofollow noreferrer">essays have been written</a> about why it is impossible, but I feel like I'm so close that there must be a way. Is there anything obvious that I'm missing?</p>
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    1. USDavid Citron
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    1. CONote that it's not clear whether `#define new` is guaranteed to work: http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#369
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      1. USJohannes Schaub - litb
    2. CO@JohannesSchaub-litb But what it is clear is that you invoke UB if you also include any standard header after that.
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    3. CODo _not_ ever try to `#define` any keyword, or name of standard function, type, object, template, etc., in any header: including a standard header file, after you have done such a `#define`, has undefined behavior.
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