The register-protocol optimization is not enabled when the interpreter is enabled

[rolfbjarne]

See:

xamarin-macios/tools/common/Optimizations.cs

Line 268 in f29834a

RegisterProtocols = (app.Registrar == RegistrarMode.Static || app.Registrar == RegistrarMode.ManagedStatic) && !app.UseInterpreter;

The register-protocol optimization is used to determine whether static interface constructors from the managed-static registrar are trimmed away or not:

xamarin-macios/tools/linker/CoreOptimizeGeneratedCode.cs

Lines 1365 to 1377 in f29834a

	bool ProcessProtocolInterfaceStaticConstructor (MethodDefinition method)
	{
	// The static cctor in protocol interfaces exists only to preserve the protocol's members, for inspection by the registrar(s).
	// If we're registering protocols, then we don't need to preserve protocol members, because the registrar
	// already knows everything about it => we can remove the static cctor.
	if (!(method.DeclaringType.IsInterface && method.DeclaringType.IsInterface && method.IsStatic && method.IsConstructor && method.HasBody))
	return false;
	if (Optimizations.RegisterProtocols != true) {
	Driver.Log (4, "Did not optimize static constructor in the protocol interface {0}: the 'register-protocols' optimization is disabled.", method.DeclaringType.FullName);
	return false;
	}

and this is required to get smaller apps + not reference frameworks unnecessarily (see #21002).

The current workaround is to add this to the csproj:

<PropertyGroup>
	<MtouchExtraArgs>--optimize:register-protocols</MtouchExtraArgs>
</PropertyGroup>

[rolfbjarne]

Potential fix:

The register-protocol optimization is required to be able to remove the static interface constructors (because otherwise the removed static constructors are needed at runtime), so the only other option is to apply the register-protocol optimization even when the interpreter is enabled. At the moment I can't see any reason why this shouldn't work.