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Asked: 2026-05-13T05:30:19+00:00

Task: Application written in Delphi accepts a structure ( record in terms of Delphi)

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Task:

Application written in Delphi accepts a structure (record in terms of Delphi) of three fields. I can send the pointer of this structure using SendMessage (Win32 API) function.

So a question is:

How to maintain certain structure representation in memory for Delphi in terms of Delphi?

It has type

PWPModPostData = ^ TWPModPostData;
TWPModPostData = record
   DataType: Integer;
   Data: PChar;
   Next: PWPModPostData;
end;

How to define it in C? I mean, is there any hidden or service fields in Delphi structures?

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1 Answer

  1. Editorial Team

    No, there are no hidden fields, and Delphi records and C structs can be mapped to each other 1:1, with a few caveats:

    • Don’t use any data type C doesn’t
      understand. This includes objects,
      dynamic arrays, and Delphi strings.

    • C and Delphi sometimes have different
      ideas about how to byte-align fields.
      Test your records and verify that
      they work on the C side. If they
      don’t, try using packed record
      instead of record.

    • When passing a pointer to a record
      from C to Delphi or vice versa, make
      sure that the side receiving it
      doesn’t try to free or reallocate the
      memory. It belongs to the memory
      manager that created it.

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