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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘Delphi’ Category

Howto create C-Header for Delphi/Free Pascal/Lazarus DLL – data types – Stack Overflow

Posted by jpluimers on 2021/09/23

From a long time ago, but got a request for it a while ago is [WayBack/] Howto create C-Header for Delphi/Free Pascal/Lazarus DLL – data types – Stack Overflow:

I have used the below construct to generate header files compatible with the C-mode compiler of Visual C++ 6 from Delphi 5 code when Delphi had the -JPH switch (see notes below).
Note that I have not used this since Delphi 5, but the switch has since then been expanded:
Somewhere along the line, the [WayBackJPHNE switch has been added to the dcc32 command-line compiler:
  -JPHNE = Generate C++ .obj file, .hpp file, in namespace, export all
It certainly does not handle all types, and you will need quite a bit of [Archive.isHPPEMIT and [Archive.isEXTERNALSYM directives.
It generates the .hpp files to import the DLL that was written in Delphi.
Notes from the Delphi 5 era:
{ Visual C++ 6 does not like nested structs/unions the way that BC++ can handle them.
  Visual C++ 6 requires the "typedef" to be present AND the typename AFTER the struct definition.
  You will see this when defining TConversationId, TReturnKey and other types that depend on nested structs/unions

  The trick is to perform these steps each and every time this unit changes:
    - Generate this unit once with all the EXTERNALSYM disabled.
      - Then the DCC32 -JPH will generate the basic structs for them.
    - Copy all the nested struct and union definitions to this file
    - Embed the definitions with (*$HPPEMIT '' *)
    - Append the typename at the end of the struct definition
    - Enable all the EXTERNALSYM again
    - Regenerate the HPP files by using DCC32 -JPH
  To make this process easier, we have introduced two new conditional defines:
    - BCB - disable EXTERNALSYM, disable HPPEMIT
    - VC6 - enable EXTERNALSYM, enable HPPEMIT

  A similar thing is with these constructions that VC6 does not like those either:
    - short strings (BCB defines them as "SmallString<##>" which VC6 does not like).
    - short integers (BCB defines them as "Shortint" so we have included an HPPEMIT for that)

{$ifdef win32}
  { important! Makes sure that the all enumerated types fit in exactly one byte each! }

  { force the C/C++ HPP header files to have the C/C++ compiler pack structure elements on byte boundaries }
  {$ifdef BCB}
    {$HPPEMIT '#pragma option push -a1' }
  {$endif BCB}
{$endif win32}

And the download (hopefully I have converted it to git by then):

The link to the converter is now []… – Delphi Coder


Posted in Delphi, Delphi 5, Development, Software Development | Leave a Comment »

Some links that might help use SonarQube with Delphi

Posted by jpluimers on 2021/08/31

For my link archive:


Posted in Delphi, Development, Software Development | Leave a Comment »

Some links on Flux outside React.js

Posted by jpluimers on 2021/08/24

The Flux architecture is often used in ReactJS, but there are also implementations outside that realm.

So here are some links for my archive:


Posted in .NET, C#, Delphi, Development, JavaScript/ECMAScript, ReactJS, Scripting, Software Development | Leave a Comment »

delphi – How to embed the MIDAS.DLL in the client executable – Stack Overflow

Posted by jpluimers on 2021/08/17

I hardly use the [WayBack] TClientDataSet Class any more, so every once in a while I bump into a legacy project that does.

Often that forgets provide a deployment list, so usually with deployment of the underlying DLL is forgotten.

Those moments, it slips my mind that the original name for the underlying DataSnap technology is called MIDAS, and the DLL is MIDAS.DLL. Sometimes even a wrong version of that DLL is distributed (unicode versus non-unicode still can still be a thing).

You can avoid loading it (often at a premium of reduced speed) my adding MidasLib to the uses list of any unit in your project:

When you use BPLs instead of full units, then missing this can lead to a nasty access violation like this one where the ClientDataSet cannot be created because the wrong Midas.dll (non-unicode) was loaded, see the screenshot and stack overflow below.

Lessons re-learned:

  1. Use a minimal deployment footprint
  2. Ensure your test systems are clean, so no older versions of dependencies can be loaded at any time.

OS EAccessViolation at adress 5110E007: Access violation at address 5110E007 in module 'dsnap250.bpl'. Read of address 00000000
{occured in main thread}

[50060B13]{rtl250.bpl  } System.@HandleAnyException
[00404815]{GVS.exe     } FastMM4.CalculateHeaderCheckSum$qqrp29Fastmm4.TFullDebugBlockHeader (Line 9098, "FastMM4.pas" + 1)
[50060039]{rtl250.bpl  } System.@AfterConstruction
[00404815]{GVS.exe     } FastMM4.CalculateHeaderCheckSum$qqrp29Fastmm4.TFullDebugBlockHeader (Line 9098, "FastMM4.pas" + 1)
[00404824]{GVS.exe     } FastMM4.UpdateHeaderAndFooterCheckSums$qqrp29Fastmm4.TFullDebugBlockHeader (Line 9108, "FastMM4.pas" + 1)
[004057C6]{GVS.exe     } FastMM4.DebugGetMem$qqri (Line 9649, "FastMM4.pas" + 42)
[00405817]{GVS.exe     } FastMM4.DebugGetMem$qqri (Line 9686, "FastMM4.pas" + 79)
[5005A247]{rtl250.bpl  } System.@ReallocMem
[50065674]{rtl250.bpl  } System.DynArraySetLength
[50065715]{rtl250.bpl  } System.@DynArraySetLength
[5110D001]{dsnap250.bpl} Datasnap.Dbclient.TCustomClientDataSet.CreateDSBase
[51111571]{dsnap250.bpl} Datasnap.Dbclient.TCustomClientDataSet.CreateDataSet
[500E920D]{rtl250.bpl  } System.Rtti.TValue._op_Implicit
[00559D29]{CDSDemo.exe } MainDataModuleUnit.TMainDataModule.DataModuleCreate (Line 50, "MainDataModuleUnit.pas" + 1)
[5016E7EF]{rtl250.bpl  } System.Classes.TDataModule.DoCreate
[5016E69C]{rtl250.bpl  } System.Classes.TDataModule.AfterConstruction
[50060039]{rtl250.bpl  } System.@AfterConstruction
[5016E67A]{rtl250.bpl  } System.Classes.TDataModule
[00544941]{CDSDemo.exe } MainFormUnit.TMainForm.PageControlChange (Line 30, "MainFormUnit.pas" + 19)
[0054598B]{CDSDemo.exe } MainFormUnit.TMainForm.FormShow (Line 40, "MainFormUnit.pas" + 47)
[50C075DD]{vcl250.bpl  } Vcl.Forms.TCustomForm.DoShow
[50C0BF7D]{vcl250.bpl  } Vcl.Forms.TCustomForm.CMShowingChanged
[5005FD9F]{rtl250.bpl  } System.TObject.Dispatch
[50AC4C16]{vcl250.bpl  } Vcl.Controls.TControl.WndProc
[50AC97FB]{vcl250.bpl  } Vcl.Controls.TWinControl.WndProc
[50C080B5]{vcl250.bpl  } Vcl.Forms.TCustomForm.WndProc
[50AC4850]{vcl250.bpl  } Vcl.Controls.TControl.Perform
[50AC8B71]{vcl250.bpl  } Vcl.Controls.TWinControl.UpdateShowing
[50AC8C80]{vcl250.bpl  } Vcl.Controls.TWinControl.UpdateControlState
[50ACB9D6]{vcl250.bpl  } Vcl.Controls.TWinControl.CMVisibleChanged
[50AC4C16]{vcl250.bpl  } Vcl.Controls.TControl.WndProc
[50AC97FB]{vcl250.bpl  } Vcl.Controls.TWinControl.WndProc
[50C080B5]{vcl250.bpl  } Vcl.Forms.TCustomForm.WndProc
[50C0E597]{vcl250.bpl  } Vcl.Forms.TScreen.GetMonitor
[50C094C5]{vcl250.bpl  } Vcl.Forms.TCustomForm.SetWindowToMonitor
[50AC4850]{vcl250.bpl  } Vcl.Controls.TControl.Perform
[50AC31E6]{vcl250.bpl  } Vcl.Controls.TControl.SetVisible
[50C078C1]{vcl250.bpl  } Vcl.Forms.TCustomForm.SetVisible
[50C11DCF]{vcl250.bpl  } Vcl.Forms.TApplication.Run
[004B3B28]{CDSDemo.exe } VclApplication.TApplication.Run (Line 113, "VclApplication.pas" + 1)
(00161097){CDSDemo.exe } [00562097]


Posted in Delphi, Development, Software Development | Leave a Comment »

Some links on the Delphi VolatileAttribute

Posted by jpluimers on 2021/08/12

Some links, because I had a hard time finding good documentation on VolatileAttribute (which is the name of the type; you use it as [Volatile] on variables, parameters and fields.



The volatile attribute is used to mark fields that are subject to change by different threads, so that code generation does not optimize copying the value in a register or another temporary memory location.

You can use the volatile attribute to mark the following declarations:

You cannot use the volatile attribute to mark the following declarations:

    TMyClass = class
        [volatile] FMyVariable: TMyType;


Read the rest of this entry »

Posted in Delphi, Development, Software Development | Leave a Comment »

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