Record the first-registered serializer's tracking flag on save#350
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Since 1.85, a Derived object serialized through a Base pointer across module boundaries loses its data on load: the base subobject reads back empty. PR #287 changed save to decide whether to emit an object id from `co.m_bos_ptr` (the first serializer instance registered for a type), but left the tracking flag written into the class preamble taken from `bos`, the instance the current call happens to use. Those can differ. With `track_selectively`, two module-local serializer singletons for one type report different `tracking()`: the one whose pointer serializer has been registered has `serialized_as_pointer()` true, the other false. The writer then records one flag but lays the object out per the other, so the reader desyncs and the subobject is misread. Record `co.m_bos_ptr`'s flag, the same instance the id decision uses, so save is self-consistent again, as it was before PR #287 when both sides read `bos`. The output is byte-identical whenever `co.m_bos_ptr == &bos` (every single-module archive); only the already-broken cross-module case changes. Fixes issue #329.
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Since 1.85, a Derived object serialized through a Base pointer across module boundaries loses its data on load: the base subobject reads back empty. PR #287 changed save to decide whether to emit an object id from
co.m_bos_ptr(the first serializer instance registered for a type), but left the tracking flag written into the class preamble taken frombos, the instance the current call happens to use.Those can differ. With
track_selectively, two module-local serializer singletons for one type report differenttracking(): the one whose pointer serializer has been registered hasserialized_as_pointer()true, the other false. The writer then records one flag but lays the object out per the other, so the reader desyncs and the subobject is misread.Record
co.m_bos_ptr's flag, the same instance the id decision uses, so save is self-consistent again, as it was before PR #287 when both sides readbos. The output is byte-identical wheneverco.m_bos_ptr == &bos(every single-module archive); only the already-broken cross-module case changes.Fixes issue #329.