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POWhy does the value of a block of memory which stores a integer change repeatedly?
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  1. POWhy does the value of a block of memory which stores a integer change repeatedly?
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    copied!<p>First of all, I define an integer pointer and class <code>A</code>. I want to pass a pointer to <code>A</code>'s method to store it.</p> <p>I found that the integer member of class <code>A</code> always changes when I invoke a method of <code>A</code>.</p> <p>I'm confused about how to avoid those changes.</p> <pre><code>#include &lt;IOSTREAM&gt; using namespace std; class A { private: int* a; public: A() { }; ~A() { }; void setA(int n) { cout &lt;&lt; "n == " &lt;&lt; n &lt;&lt; "&amp;n == " &lt;&lt; &amp;n &lt;&lt; endl; a = &amp;n; cout &lt;&lt; "now a== " &lt;&lt; a &lt;&lt; endl; } void PassA(int* &amp;outint) { cout &lt;&lt; "a == " &lt;&lt; a &lt;&lt; " *a == " &lt;&lt; *a &lt;&lt;endl; outint = a; cout &lt;&lt; "outint = " &lt;&lt; outint &lt;&lt; endl; } void Print() { cout &lt;&lt; "a ==================== " &lt;&lt; a &lt;&lt; endl; cout &lt;&lt; "*a ==================== " &lt;&lt; *a &lt;&lt; endl; } }; int main() { A A_1; int num = 5; A_1.setA(num); int *intb= NULL ; A_1.PassA(intb); //When the line above done,the value of A_1.a will change. cout &lt;&lt; "intb == " &lt;&lt; intb &lt;&lt; endl; cout &lt;&lt; "*intb ==" &lt;&lt; *intb &lt;&lt; endl; cout &lt;&lt; "num ==" &lt;&lt; num &lt;&lt; endl; A_1.Print(); return 0; } </code></pre> <p><b>Output:</b></p> <pre> n == 5&n == 0x28fe90 now a== 0x28fe90 a == 0x28fe90 *a == 2686708 outint = 0x28fe90 intb == 0x28fe90 *intb ==4619604 num ==5 a ==================== 0x28fe90 *a ==================== 4619604 </pre>
 

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