Delphi: How to get rid of “Ancestor of TMyForm not found error’

First, for those who don't know how to inherit a form visually, you create the ancestor form as usual. Then go to File > New > Other. Select the tab with the name of the current project, and choose the form you want to inherit from. If you want to inherit from a form that's not part of the current project, open that form, right click it, and choose Add to Repository. Then you will be able to go to File > New > Other and select that form from the appropriate tab.

Given that, I came across issues because some of the descendant forms were already created, so I couldn't follow the process above. Also, I made some changes to forms from the standard code Delphi creates. I was able to resolve all issues with visual form inheritance using the following guidelines:

• The .pas file of the descendant form must have the form's class inherit from the correct ancestor class, e.g.:
  type TMyForm = class(TAncestorForm)
• The first line in the .dfm of the descendant form must have the word inherited instead of object, e.g.:
  inherited MyForm: TMyForm
• EDIT: After double checking, the following is NOT required: The .pas file of the ancestor form must have the standard global variable that Delphi creates, e.g.:
  var AncestorForm: TAncestorForm;
• The uses section of the .dpr file of the project must have that same global variable as a comment after the unit's file name, e.g.:
  unAncestor in 'unAncestor.pas' {AncestorForm}

Notes/Tips:

• Both the ancestor form and the descendant form are allowed to be non-auto created if you want (Set in Project > Options > Forms > Auto-create forms).
• To revert a property on a descendant form to the ancestor form's value, right click on the property in the Object Inspector, and choose Revert to inherited.
• To revert all property values of a component to the ancestor's values, right click the component and choose Revert to inherited.

We are investigating the issue. In short, it depends on the potential mis-alignment (to 32 boundary) of the Integer referenced by a pointer. Need a little more time to have all of the answers... and a plan to address this.

Marco Cantù, moderator on Delphi Developers

Also reference Why are the Delphi zlib and zip libraries so slow under 64 bit? as Win64 libraries are shipped built without optimizations.

In the QP Report: RSP-9922 Bad ARM code produced by the compiler, $O directive ignored?, Marco added following explanation:

There are multiple issues here:

• As indicated, optimization settings apply only to entire unit files and not to individual functions. Simply put, turning optimization on and off in the same file will have no effect.
• Furthermore, simply having "Debug information" enabled turns off optimization. Thus, when one is debugging, explicitly turning on optimizations will have no effect. Consequently, the CPU view in the IDE will not be able to display a disassembled view of optimized code.
• Third, loading non-aligned 64bit data is not safe and does result in errors, hence the separate 4 one byte operations that are needed in given scenarios.