Re: [Dev-C++] getting unexpected results

[Damien <g_...@ho...>]

<html><div style='background-color:'><P align=left>Hello Dawood,</P>
<P align=left>Firstly, that 'char *buf' declaration: allocate some memory to it using <STRONG>new</STRONG> or <STRONG>malloc. </STRONG>Passing such a pointer to <STRONG>cin is dangerous</STRONG>( it crashed on my WinXP).&nbsp; The reason why it won't work how you would like it is because str_ex[0] and str_ex[1] point to the <STRONG>same</STRONG> memory address (at&nbsp; buf), so if buf is changed, the other pointers that point to buf will change as well(str_ex[0] and str_ex[2]).&nbsp; I suggest giving the cstr member of each structure its own memory space, and copy the buf into each as seen below.</P>
<P align=left>#include &lt;iostream.h&gt; <BR>#include &lt;stdlib.h&gt; <BR>#include &lt;string.h&gt;<BR>int main() <BR>{ <BR>&nbsp; struct str_misc { <BR>&nbsp;&nbsp;&nbsp; char* cstr; <BR>&nbsp; }; <BR>&nbsp; str_misc str_ex[2]; <BR>&nbsp; char* buf = new char[50];</P>
<P align=left>&nbsp; cin&gt;&gt;buf; <BR>&nbsp; str_ex[0].cstr = new char[50];<BR>&nbsp; <BR>&nbsp; strncpy(str_ex[0].cstr,buf,49);<BR>&nbsp; <BR>&nbsp; cout&lt;&lt;str_ex[0].cstr&lt;&lt;"index=0"&lt;&lt;'\n'; </P>
<P align=left>&nbsp; cin&gt;&gt;buf; <BR>&nbsp; <BR>&nbsp; str_ex[1].cstr = new char[50]; <BR>&nbsp; <BR>&nbsp; strncpy(str_ex[1].cstr,buf,49);<BR>&nbsp; <BR>&nbsp; cout&lt;&lt;str_ex[1].cstr&lt;&lt;"index=1"&lt;&lt;'\n'; </P>
<P align=left>&nbsp; cout&lt;&lt;str_ex[0].cstr&lt;&lt;" repeat index=0"&lt;&lt;'\n'; <BR>&nbsp; cout&lt;&lt;str_ex[1].cstr&lt;&lt;" repeat index=1"&lt;&lt;'\n'; <BR>&nbsp; delete str_ex[0].cstr;<BR>&nbsp; delete str_ex[1].cstr;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; system("PAUSE");<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return 0; <BR>} <BR><BR></P>
<DIV></DIV>----Original Message Follows---- 
<DIV></DIV>From: dawood <DA...@KU...>
<DIV></DIV>To: Dev C++ <DEV...@LI...>
<DIV></DIV>Subject: [Dev-C++] getting unexpected results 
<DIV></DIV>Date: Tue, 22 Jul 2003 19:50:51 +0800 
<DIV></DIV>
<DIV></DIV>Can anybody let me know, why the below code is not working correctly. 
<DIV></DIV>
<DIV></DIV>#include <IOSTREAM.H>
<DIV></DIV>#include <STDLIB.H>
<DIV></DIV>
<DIV></DIV>int main() 
<DIV></DIV>{ 
<DIV></DIV>struct str_misc { 
<DIV></DIV>char* cstr; 
<DIV></DIV>}; 
<DIV></DIV>str_misc str_ex[12]; 
<DIV></DIV>char* buf; 
<DIV></DIV>
<DIV></DIV>cin&gt;&gt;buf; 
<DIV></DIV>str_ex[0].cstr= buf; 
<DIV></DIV>cout&lt;<STR_EX[0].CSTR<<"INDEX=0"<<'\N'; DIV <> 
<DIV></DIV>cin&gt;&gt;buf; 
<DIV></DIV>str_ex[1].cstr= buf; 
<DIV></DIV>cout&lt;<STR_EX[1].CSTR<<"INDEX=1"<<'\N'; DIV <> 
<DIV></DIV>cout&lt;<STR_EX[0].CSTR<<" DIV < index="0&quot;<<'\n';" repeat> cout&lt;<STR_EX[1].CSTR<<" DIV < index="1&quot;<<'\n';" repeat> 
<DIV></DIV>system("PAUSE"); 
<DIV></DIV>return 0; 
<DIV></DIV>} 
<DIV></DIV>
<DIV></DIV>
<DIV></DIV>
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