[odb-users] Virtual std::vector< odb::lazy_shared_ptr<X> > crashes odb compiler

[Boris Kolpackov]

Hi Dieter,

Thanks for the test case. This is a pretty hairy problem that has to do
with lazy template instantiation in C++. In essence, since your lazy_ptr
is not used anywhere else except as an element in a container in a
virtual data member, it doesn't get instantiated.

There is not much we can do to handle this automagically (instantiating
things on the fly is possible but would require incremental re-parsing of
the instantiated classes into the ODB's semantics graph). Though crashing
is also not right. So I've fixed it to issue proper diagnostics. Now for
your test case ODB prints:

test.h:51:16: error: container element type is not instantiated
test.h:51:16: info: use typedef/using to instantiate

As suggested in the diagnostics, the workaround is to force the (shallow)
instantiation with a typedef, for example:

typedef odb::lazy_shared_ptr<Employee> EmployeeLazyPtr;

Boris