IfThen (Assigned (Widget), Widget.Description, "No Widget") is not crashing. Should it?

Question

In the code that I support, I found some code examples that look like this:

Description := IfThen(Assigned(Widget), Widget.Description, 'No Widget');

I expected this to work when the widget is zero, but when I tested it, it worked great.

If I recompile it with the code control disabled in Project - Options - Compiler, I get an access violation.

It seems that since IfThen is marked as inline, the compiler usually does not evaluate Widget.Description if Widget is zero.

Is there a reason why the code should be “fixed” because it does not seem to be broken? They do not want the code to be changed unnecessarily. Could this bite them?

I tested it with Delphi XE2 and XE6.

Answer 1

Personally, I hate relying on behavior that is not contractual.

The built-in directive is a compiler suggestion.

If I understand correctly what I read, your code will also be broken if you create using runtime packages.

nesting never occurs across package boundaries

As Uli Gerhardt commented, this can be considered a mistake, in which she works in the first place. Since behavior is not contractual, it can change at any time.

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Answer 2

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Answer 3

It has already been fixed - in XE7 and confirmed that this should have been a misbehavior.

See https://quality.embarcadero.com/browse/RSP-11531