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C++-DLL and Delphi 3

Posted on 1998-11-09
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Last Modified: 2010-04-04
Hello,

I've written a DLL in Borland C++ 5.0.  One of the functions is a simple
concatenation function :

char* __stdcall _export StringTest(char* Str1, char* Str2)
{
   char* tmp;

   int l1 = strlen(Str1);
   int l2 = strlen(Str2);

   tmp = (char*) malloc(l1+l2+1);
   strcpy(tmp, Str1);
   strcat(tmp,Str2);
   return tmp;
}

This function works fine, but it has a memory leak : the memory
allocated for tmp is not released.

This function is called from a Delphi 3 application.  Can anyone tell me
how I can release the allocated memory, prefarably from the Delphi
application ?
I've tried freeing the memory just before the return instruction, but it
doesn't work.

Thanks in advance,

Johan

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Question by:ppr
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1 Comment
 
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Accepted Solution

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AndersWP earned 600 total points
ID: 1346252
ppr:

To manage memory from both Delphi and Borland C++ (or any other windows programming tool), you should use the WinAPI memory functions. I have written two code snippets in Pascal that shows how to do malloc- and free-like functions using the WinAPI. I trust you can convert to C (or whatever) and add error handling as needed:

Function WinMalloc(aSize: Integer): Pointer;

Begin
  Result:=Pointer(GlobalAlloc(GMEM_FIXED, aSize));
End;

Procedure WinFree(aPointer: Pointer);

Begin
    GlobalFree(GlobalHandle(aPointer));
End;

I hope this will help,

AndersWP
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