EInvalidCast in Freepascal/Lazarus when -CR option is enabled

[rlebeau]

If a user compiles Indy directly into a Freepascal/Lazarus project without installing it as a package, and if that project has the -CR compiler option enabled, then EInvalidCast errors can occur at runtime, such as inside of TIdThread.Cleanup(), for example.

See: https://forum.lazarus.freepascal.org/index.php/topic,63996.0.html Also: https://forum.lazarus.freepascal.org/index.php?topic=58944.msg486254#msg486254

This is because several areas of Indy use Delphi-style accessor classes to access protected class members across unit boundaries, but -CR can silently convert object hard-casts into the as operator, which obviously won't work for accessor classes as they require hard-casting to operate properly (since objects being casted don't derive from the accessor class itself).

Unknown whether -CR can be detected/disabled dynamically in code or not. If not, the only workaround I can think of is to re-engineer the affected areas of Indy to either 1) make protected members be public, or 2) use private interfaces to access the protected members.

[rlebeau]

Possible workaround - use FreePascal's {$objectChecks off} directive wherever Indy uses an accessor class, for example:

{$push}
{$objectChecks off}
LScheduler := TIdYarnOfThreadAccess(FYarn).FScheduler;
{$pop}