TypeInfo in struct ABI

Teodor Dutu teodor.dutu at gmail.com
Mon Jan 17 15:26:46 UTC 2022


In order to allocate a `struct` type, two DRuntime hooks are 
used: `_d_newitemT` for uninitialised structs and `_d_newitemiT` 
for initialised ones. Both hooks call `_d_newitemU`, which 
allocates memory for the struct and [writes the struct’s 
`TypeInfo`](https://github.com/dlang/druntime/blob/9d99b1ccd90d1e66c31e27cc71b8a266612aa14a/src/rt/lifetime.d#L1122) at the end of the allocated chunk.

We now attempt to convert these hooks to templates, with the goal 
of not using `TypeInfo` at all. However, the fact that the ABI of 
a struct contains its `TypeInfo` prevents us from achieving this 
goal. Is this `TypeInfo` object still necessary for anything, or 
are we free to remove it from the ABI altogether so that we have 
cleaner implementations for `_d_newitem{U,iT,T}`?


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