Implement Write Barrier and dsize for FFI::StructLayout #1006
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And FFI::StructLayout::Field Write barrier protected objects are allowed to be promoted to the old generation, which means they only get marked on major GC. The downside is that the RB_BJ_WRITE macro MUST be used to set references, otherwise the referenced object may be garbaged collected. This commit also implement a `dsize` function so that these instance report a more relevant size in various memory profilers. I had to get rid of the `memset(0)` in `struct_layout_mark` has with Write Barriers it's not guaranteed that the layout will be marked before `fieldName` is moved. I don't think it was a good fix anyway, it's better to mark these VALUE so the GC pin them. I think we could go back to an `st_table` and mark only the keys with `rb_mark_set`. But I didn't want to go down this rabbit hole.
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And FFI::StructLayout::Field
Ref: #991
Write barrier protected objects are allowed to be promoted to the old generation, which means they only get marked on major GC.
The downside is that the RB_BJ_WRITE macro MUST be used to set references, otherwise the referenced object may be garbaged collected.
This commit also implement a
dsizefunction so that these instance report a more relevant size in various memory profilers.I had to get rid of the
memset(0)instruct_layout_markhas with Write Barriers it's not guaranteed that the layout will be marked beforefieldNameis moved.I don't think it was a good fix anyway, it's better to mark these VALUE so the GC pin them. I think we could go back to an
st_tableand mark only the keys withrb_mark_set. But I didn't want to go down this rabbit hole.