In the end I did this.
var TitleStr: string='The DLL Title'; var Title: pChar; Title := @TitleStr[1]; I could then use CopyStr elsewhere. Cheers. From: [email protected] [mailto:[email protected]] On Behalf Of Bevan Edwards Sent: Sunday, 12 May 2013 7:52 PM To: NZ Borland Developers Group - Delphi List Subject: Re: [DUG] StrCopy problem Hi Ross, 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. 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. By using: a:=AllocMem(10); StrCopy(a, 'abcdefghi'); b:='jklmnopqr'; StrCopy(a, b); The variable 'b' now points to application memory while 'a' is allocated a "write-enabled" memory address, so the access violation doesn't occur. Regards, Bevan On 12/05/2013 5:30 p.m., Ross Levis wrote: 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. Ross. From: [email protected] [mailto:[email protected]] On Behalf Of Bevan Edwards Sent: Sunday, 12 May 2013 4:48 PM To: [email protected] Subject: Re: [DUG] StrCopy problem 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? Have you tried allocating 10 bytes of memory to 'a' and then using StrCopy? Have you run the debugger and checked where the PChars 'a' and 'b' are pointing to before StrCopy? -------- Original message -------- From: Ross Levis <[email protected]> Date: To: 'NZ Borland Developers Group - Delphi List' <[email protected]> Subject: Re: [DUG] StrCopy problem Doesn't really help. 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. Ross. From: [email protected] [mailto:[email protected]] On Behalf Of Keith Allpress Sent: Sunday, 12 May 2013 10:27 AM To: 'NZ Borland Developers Group - Delphi List' Subject: Re: [DUG] StrCopy problem Perhaps: http://rvelthuis.de/articles/articles-pchars.html From: [email protected] [mailto:[email protected]] On Behalf Of Ross Levis Sent: Sunday, 12 May 2013 2:39 a.m. To: 'NZ Borland Developers Group - Delphi List' Subject: [DUG] StrCopy problem var a: pChar; b: pChar; begin a := 'abcdefghi'; b := 'jklmnopqr'; StrCopy(a,b); end; Question: Why does this code crash? _______________________________________________ NZ Borland Developers Group - Delphi mailing list Post: [email protected] Admin: http://delphi.org.nz/mailman/listinfo/delphi Unsubscribe: send an email to [email protected] with Subject: unsubscribe
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