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Editorial Team
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Asked: 2026-05-18T08:32:42+00:00

I’m allocating memory for several PWideChar on my main executable file var pwcValor: PWideChar;

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I’m allocating memory for several PWideChar on my main executable file

var
  pwcValor: PWideChar;
begin
  pwcValor := AllocMem( sizeof(WideChar) * Succ(Length(pValor)));
  StringToWideChar(pValor, pwcValor, Succ(Length(pValor)));
  pMetodo(pCodigo, pCodigoParametro, pwcValor);

All of these variables are sent over to an external DLL using late binding. I have some questions about this situation to avoid memory leaks.

  • Where (on my exe or my dll) should I call the FreeMem on these variables?
  • Do I need to call FreeMem on these variables?
  • When can I (or should I) call FreeMem on these variables?

If I call them inside the external DLL (which is also mine), I get Access Violations when I try to Unload from memory the DLL library.
Tks

EDIT

Something I forgot to ask. And the other way around? I have so return parameters from my DLL to the EXE, so the PWideChars are allocated on the DLL. So, I would have to free them on the DLL, right? But I’ll probably still be using them on the EXE. Must I pre-allocate on the EXE, send to the DLL the pointer, and have it filled in the DLL in these cases? Or just make a copy on the EXE of the returned parameter, so I can free it safely on the DLL?

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1 Answer

  1. Editorial Team

    Ultimately that depends on the design of the DLLs you use. However, I would say that if not documented otherwise it is safe to free the resources as soon as the DLL function returns. I would even suggest that you should do it. Anyway you must do it to avoid memory leaks.

    Regarding the last sentence, a DLL and the invoking EXE eventhough they both be Delphi code, they use different memory managers, so you cannot in a DLL free memory allocated in the EXE.

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