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POThis pointer suddenly becomes 0x0 in C++
 

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  1. POThis pointer suddenly becomes 0x0 in C++
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    <p>I have an (apparently) very simple class initialization, with two constructors, and when I want to create a new Friendship, the this pointer of the first argument has the appropriate pointer value, but the second doesn't. </p> <p>I'll explain better in code - this is one my constructors:</p> <pre><code>Friendship::Friendship(const User &amp;u1, const User &amp;u2){ *user1 = u1; *user2 = u2; } </code></pre> <p>When I do this in my Test class:</p> <pre><code>bool Test::insertFriendship(User *user1, User *user2) { bool friendshipExists = verifyFriendship(user1, user2); if(!friendshipExists) { friendships.push_back(new Friendship(*user1, *user2)); // this is a ptr_vector container return true; } return false; } </code></pre> <p>It gives me a EXC_BAD_ACCESS error at the push_back line because apparently the 'this' pointer of the user1 WORKS when it gets to the constructor and it points to a valid memory address, but when it goes to do the user2, the 'this' pointer of user2 points to 0x0 and it fails because that's basically trying to re-deference NULL when it gets to the operator = overload.</p> <p>Ex: when it tries to create a new Friendship:</p> <p>this->user1's mem address = 0x100100b20 this->user2's mem address = 0x0 - error!</p> <p>while </p> <p>u1's mem address = 0x7fff5fbff900 u2's mem address = 0x7fff5fbff898</p> <p>I mean, these u1 and u2 mem addresses are valid so why the heck doesn't it work when I try to do:</p> <pre><code>*user1 = u1; //works cos this is 0x100100b20 *user2 = u2; // fails cos this is 0x0 even though u2 is a valid mem address! </code></pre> <p>Anyone know why this strange behavior? Even if I switch user1 and user2 in my push_back, it still won't work at the SECOND one. It's always that pesky second one that never works.</p> <p>Ah, this is my Friendship header file, nothing too complex.</p> <pre><code>#include "User.h" #ifndef Friendship_h #define Friendship_h class Friendship { friend class Test; protected: User *user1; User *user2; public: Friendship(const User &amp;u1, const User &amp;u2); Friendship(const Friendship &amp;a); ~Friendship(); }; #endif </code></pre>
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    1. CODon't use pointers. Nobody knows how to use pointers right. Guaranteed.
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    2. COIt works for the first one, and the pointers of my objects are A-ok when I pass them to the constructor, it's the goddamn 'this' pointer (which I can't manipulate to be honest) that's giving me that problem. And it works for the first time, just not the second (and I assume if I had 3 "User" object arguments, only the first one would work).
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