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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-NZ link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Thanks for clarifying that. I was stuck on that when I wanted to change a PChar variable that is allocated in a DLL using the string assignment method. I’ll have to change the DLL.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Cheers.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> delphi-bounces@listserver.123.net.nz [mailto:delphi-bounces@listserver.123.net.nz] <b>On Behalf Of </b>Bevan Edwards<br><b>Sent:</b> Sunday, 12 May 2013 7:52 PM<br><b>To:</b> NZ Borland Developers Group - Delphi List<br><b>Subject:</b> Re: [DUG] StrCopy problem<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'>Hi Ross,<br><br>You don't say which version of Delphi you're using, but I assume it's pre-Unicode support, since you use PChar instead of PAnsiChar or PWideChar.<br><br>Out of curiosity I built a small test application and traced through the source code for this snippet of code using the CPU window. What I noticed is that the address of the two strings assigned to 'a' and 'b' are part of program memory. More specifically, Delphi appears to store these strings immediately after the "return" opcode for the procedure and simply puts those addresses into 'a' and 'b'. Since this area of memory is protected while the application is running, that's why you get the error.<br><br>By using:<br>a:=AllocMem(10);<br>StrCopy(a, 'abcdefghi');<br>b:='jklmnopqr';<br>StrCopy(a, b);<br><br>The variable 'b' now points to application memory while 'a' is allocated a "write-enabled" memory address, so the access violation doesn't occur.<br><br>Regards,<br><br>Bevan<br><br><br><o:p></o:p></p><div><p class=MsoNormal>On 12/05/2013 5:30 p.m., Ross Levis wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'>I did see a & b had a pointer address allocated. It looked like a normal pointer address range. I’ll try allocating 10 bytes to a later and see what happens.</span><o:p></o:p></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'>Ross.</span><o:p></o:p></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> <a href="mailto:delphi-bounces@listserver.123.net.nz">delphi-bounces@listserver.123.net.nz</a> [<a href="mailto:delphi-bounces@listserver.123.net.nz">mailto:delphi-bounces@listserver.123.net.nz</a>] <b>On Behalf Of </b>Bevan Edwards<br><b>Sent:</b> Sunday, 12 May 2013 4:48 PM<br><b>To:</b> <a href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a><br><b>Subject:</b> Re: [DUG] StrCopy problem</span><o:p></o:p></p></div></div><p class=MsoNormal> <o:p></o:p></p><div><div><p class=MsoNormal>Actually, based on that article a:='abcdefghi' should assign 10 bytes and include the zero byte at the end. But I wonder if the problem is due to where this data is stored and trying to copy b to a results in an attempt to write to protected memory?<o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal>Have you tried allocating 10 bytes of memory to 'a' and then using StrCopy?<o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><p class=MsoNormal>Have you run the debugger and checked where the PChars 'a' and 'b' are pointing to before StrCopy?<o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div></div><p class=MsoNormal style='margin-bottom:12.0pt'><br><br><br>-------- Original message --------<br>From: Ross Levis <<a href="mailto:ross@stationplaylist.com">ross@stationplaylist.com</a>> <br>Date: <br>To: 'NZ Borland Developers Group - Delphi List' <<a href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a>> <br>Subject: Re: [DUG] StrCopy problem <br><br><br><o:p></o:p></p><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>Doesn’t really help.</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>a := 'abcdefghi' does allocate 9 bytes of RAM. I can access a and b after it is assigned. The problem is StrCopy crashes. I would expect “a” to have the same string as b once this is executed.</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>Ross.</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D'> <a href="mailto:delphi-bounces@listserver.123.net.nz">delphi-bounces@listserver.123.net.nz</a> [<a href="mailto:delphi-bounces@listserver.123.net.nz">mailto:delphi-bounces@listserver.123.net.nz</a>] <b>On Behalf Of </b>Keith Allpress<br><b>Sent:</b> Sunday, 12 May 2013 10:27 AM<br><b>To:</b> 'NZ Borland Developers Group - Delphi List'<br><b>Subject:</b> Re: [DUG] StrCopy problem</span><o:p></o:p></p></div></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>Perhaps:</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'><a href="http://rvelthuis.de/articles/articles-pchars.html">http://rvelthuis.de/articles/articles-pchars.html</a></span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span lang=EN-US style='color:#1F497D'>From:</span></b><span lang=EN-US style='color:#1F497D'> <a href="mailto:delphi-bounces@listserver.123.net.nz">delphi-bounces@listserver.123.net.nz</a> [<a href="mailto:delphi-bounces@listserver.123.net.nz">mailto:delphi-bounces@listserver.123.net.nz</a>] <b>On Behalf Of </b>Ross Levis<br><b>Sent:</b> Sunday, 12 May 2013 2:39 a.m.<br><b>To:</b> 'NZ Borland Developers Group - Delphi List'<br><b>Subject:</b> [DUG] StrCopy problem</span><o:p></o:p></p></div></div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>var</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> a: pChar;</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> b: pChar;</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>begin</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> a := 'abcdefghi';</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> b := 'jklmnopqr';</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> StrCopy(a,b);</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>end;</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'>Question: Why does this code crash?</span><o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='color:#1F497D'> </span><o:p></o:p></p></div></div><p class=MsoNormal><br><br><br><o:p></o:p></p><pre>_______________________________________________<o:p></o:p></pre><pre>NZ Borland Developers Group - Delphi mailing list<o:p></o:p></pre><pre>Post: <a href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a><o:p></o:p></pre><pre>Admin: <a href="http://delphi.org.nz/mailman/listinfo/delphi">http://delphi.org.nz/mailman/listinfo/delphi</a><o:p></o:p></pre><pre>Unsubscribe: send an email to <a href="mailto:delphi-request@listserver.123.net.nz">delphi-request@listserver.123.net.nz</a> with Subject: unsubscribe<o:p></o:p></pre></blockquote><p class=MsoNormal><o:p> </o:p></p></div></body></html>