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POWhy 'this' is a pointer and not a reference?
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copied!<p>I was reading the answers to this question <a href="https://stackoverflow.com/questions/385297/whats-wrong-with-c-compared-to-other-languages">C++ pros and cons</a> and got this doubt while reading the comments. </p> <blockquote> <p>programmers frequently find it confusing that "this" is a pointer but not a reference. another confusion is why "hello" is not of type std::string but evaluates to a char const* (pointer) (after array to pointer conversion) – Johannes Schaub - litb Dec 22 '08 at 1:56</p> <p>That only shows that it doesn't use the same conventions as other (later) languages. – le dorfier Dec 22 '08 at 3:35</p> <p>I'd call the "this" thing a pretty trivial issue though. And oops, thanks for catching a few errors in my examples of undefined behavior. :) Although I don't understand what info about size has to do with anything in the first one. A pointer is simply not allowed to point outside allocated memory – jalf Dec 22 '08 at 4:18</p> <p>Is this a constant poiner? – yesraaj Dec 22 '08 at 6:35</p> <p>this can be constant if the method is const int getFoo() const; <- in the scope of getFoo, "this" is constant, and is therefore readonly. This prevents bugs and provides some level of guarantee to the caller that the object won't change. – Doug T. Dec 22 '08 at 16:42</p> <p>you can't reassign "this". i.e you cannot do "this = &other;", because this is an rvalue. but this is of type T*, not of type T const . i.e it's a non-constant pointer. if you are in a const method, then it's a pointer to const. T const . but the pointer itself is nonconst – Johannes Schaub - litb Dec 22 '08 at 17:53</p> <p>think of "this" like this: #define this (this_ + 0) where the compiler creates "this_" as a pointer to the object and makes "this" a keyword. you can't assign "this" because (this_ + 0) is an rvalue. of course that's not how it is (there is no such macro), but it can help understand it – Johannes Schaub - litb Dec 22 '08 at 17:55</p> </blockquote> <p>My question is, why <code>this</code> is a pointer a not a reference? Any particular reason for making it a pointer?</p> <hr> <p>Some further arguments why <code>this</code> being a reference would make sense:</p> <ul> <li>Consider <code>Item 1</code> from <code>More Effective C++</code>: use references when it is guaranteed that we have a valid object i.e. not a NULL (my interpretation). </li> <li>Furthermore, references are considered safer than pointers (because we can't screw the memory up with a stray pointer). </li> <li>Thirdly, the syntax for accessing references (<code>.</code>) is a little bit nicer and shorter than accessing pointers (<code>-></code> or <code>(*)</code>).</li> </ul>

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