MI-L MB/Delphi - Passing strings from MB to Delphi DLL (revisited)

[Peter Zyczynski]

Hi List

I have a query relating to passing strings from MB to Delphi, by (var).

Do PChar data types in Delphi always have to be embedded inside a "Packed
Record" in order to make changes to them (VAR), or can they be passed
directly as procedure parameters?  I haven't had any success with the later
one.


-----------------------------------------------------------
This DOES work: (note the PChars snugly tucked away inside
the TName packed record data type)
-----------------------------------------------------------
unit Unit_Test;

interface
uses
    Dialogs, SysUtils;

type
    TName = packed record
        FName : pchar;
        LName : pchar;
    end;

procedure ChangeValue(var Name:TName); Stdcall;

implementation

//******************************************************
procedure ChangeValue(var Name:TName);
begin
    StrPcopy(Name.FName,'Delphi First Name'); //<-- Works fine.
    StrPcopy(Name.LName,'Delphi Last Name');  //<-- Works fine.
end;
//******************************************************
end.



-----------------------------------------------------------
This DOESN'T work: (passing strings directly into PChar types
and then making changes seems to cause memory problems)
-----------------------------------------------------------
unit Unit_Test2;

interface
uses
    Dialogs, SysUtils;

procedure ChangeValue(var FName:PChar; var LName:PChar); Stdcall;

implementation

//******************************************************
procedure ChangeValue(var FName:PChar; var LName:PChar);
begin
    StrPcopy(FName,'Delphi First Name');  //<--Everything crashes in a great
heap!
    StrPcopy(LName,'Delphi Last Name');
end;
//******************************************************
end.



Can anyone enlighten me as to why the "ChangeValue" procedure doesn't work
in the second example?


Peter Zyczynski
Analyst Programmer
Landfile Consultancy
Australia
Ph: (03) 6244-7344
email: [EMAIL PROTECTED]




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