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StrPCopy problem

Posted on 1998-07-18
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Last Modified: 2012-08-13
Hi...
   I'm just trying to do a very simple conversion of a regular old string to a PChar variable. here's my code:

StrPcopy(optparms, hoptparms);

...optparms is declared as PChar. hoptparms is declared as a string.

 Upon executing this line, the following error window appears:

"Project myproj.exe raised exception class EAccessViolation with message 'Access violation at address 00407E5D in module 'MYPROJ.EXE'. Read of address FFFFFFFF'. Process stopped. Use Step or Run to continue."

...Why? Seems like a simple enough thing to do?

Regards,
  Shawn Halfpenny
  drumme59@sprint.ca

P.S: I am using Delphi v3
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Question by:aztec
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7 Comments
 
LVL 3

Expert Comment

by:Matvey
ID: 1358175
"The destination buffer must have room for at least Length(Source)+1 characters." (Help)

Are you sure your null-terminated string is allocated corectly?
Try this:

optparms := StrAlloc(Length(hoptparms)+1);
StrPcopy(optparms, hoptparms);
0
 
LVL 2

Expert Comment

by:omsec
ID: 1358176
try first initalizing the pChar:

optparams := ;'';
0
 
LVL 3

Accepted Solution

by:
vladika earned 200 total points
ID: 1358177
1) Try simply PChar(hoptparms)

2) from help
StrPCopy does not perform any length checking.
The destination buffer must have room for at least Length(Source)+1 characters.

So,
  optparms := StrAlloc(Length(hoptparms)+1); // allocate enough space for string
  try
    StrPCopy(optparms, hoptparms); // copy string
    //  process optparms
  finally
    StrDispose(optparms); // free space
  end;

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LVL 3

Expert Comment

by:Matvey
ID: 1358178
Vladika, isn't it exactly what was said before?!!
0
 
LVL 3

Expert Comment

by:vladika
ID: 1358179
Matvey,
You are right.
But you forget about StrDispose
If space for a string is allocated with StrAlloc,
it should be deallocated via StrDispose.

I downloaded question before your comment,
so I could not see it. Sorry.


0
 
LVL 3

Expert Comment

by:vladika
ID: 1358180
Aztec,

Since you use Delphi V3 ...

From help:
.
Delphi supports three types of strings: Short strings, long strings and wide strings.
.
The long string type represents a dynamically-allocated string
with a maximum length limited only by available memory.
For new applications, it is recommended that you use the long string type.
.
Since long strings are implicitly null terminated and dynamically allocated, the use of StrAlloc is in decline

So, you can use PChar(hoptparms)

0
 

Author Comment

by:aztec
ID: 1358181
right on! Thanks!

Shawn
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