StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

POMacro to replace C++ operator new
text
Body
copied!<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>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload