Include unused class and its RTTI in the executable

[Attila Kovacs 631]

What is the simplest way to make the compiler/linker include a class and its RTTI into the executable when I have no references to the class in the code?

ATM I have an "if" with a variable in the expression which always evaluates to false and in the begin-end block a "TxyClass.Create;".

I don't really like this solution.

[Attila Kovacs 631]

I've found {$STRONGLINKTYPES ON} and this: https://code.i-harness.com/en/q/281b33c

Still curious if anyone has a different solution.

[Fritzew 51]

Simply call [TYourClass].ClassInfo somewhere in the application or in the initialization of the implementing Unit.
Should be enough

[Attila Kovacs 631]

@Fritzew Good point, thank you. ClassInfo not, but for example ClassParent does the trick. This one is the simplest for now. And ClassParent() is also very tiny.

[David Schwartz 430]

put this somewhere:

 

TMyClass.Create().Free();

 

Or add a Register() method and call it in an Initialization section somewhere.

Edited January 17, 2019 by David Schwartz

[Uwe Raabe 2064]

7 hours ago, David Schwartz said:

put this somewhere:

 

TMyClass.Create().Free();

That is pretty similar to the original approach described in the topic. In addition, there it is wrapped in a never-true condition to avoid being executed.

[David Schwartz 430]

22 hours ago, Uwe Raabe said:

That is pretty similar to the original approach described in the topic. In addition, there it is wrapped in a never-true condition to avoid being executed.

is there any guarantee that the compiler won't ever figure out the never-true condition and simple ignore the code in the block? 

 

If it's never executed then there can't be any side-effects, so why not just ignore it entirely? That would not solve the problem, would it?

 

I don't like stuff that depends on subtle compiler optimizations that can occur silently and I'd never know they happened unless I happened to look at the generated code. 

 

It's even worse than that because it would work fine in debug mode that does no optimization, but then fail when the code is built as a Release and optimization is turned on.

[Uwe Raabe 2064]

In case the compiler can evaluate that condition, that might be an issue, but there are many ways to play on the safe side there. Actually creating and freeing the class may come with some costs, though.

[Stefan Glienke 2019]

I don't see the Delphi compiler performing any control flow analysis and eliminate code in any possible future.

C++ might do that though (see https://stackoverflow.com/questions/6664471/observable-behaviour-and-compiler-freedom-to-eliminate-transform-pieces-c-co)

 

However I requested adding a way to specifically force linking of types into the binary some while ago - see https://quality.embarcadero.com/browse/RSP-18389