use MaybeUninit instead of uninitialized #412
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Latest versions of rust will panic when trying to leave an uninitialized SerializedValue from mem::uninitialized which was breaking the js! macro
RalfJung reviewed Apr 15, 2022
| *(&mut value as *mut SerializedValue as *mut $untagged_type) = untagged; | ||
| let mut value = mem::MaybeUninit::<SerializedValue>::uninit(); | ||
| *(value.as_mut_ptr() as *mut $untagged_type) = untagged; | ||
| let mut value = value.assume_init(); |
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assume_init should only be called after the tag has also been initialized.
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Also this is still wrong for many cases -- the assignment of untagged might fail to completely initialize both data_1 and data_2.
And finally, if untagged is a pointer type, then this would transmute a pointer to an integer, which is not something one should do. SerializedValue seems to be intended as a type that can hold arbitrary data, so u64 and u32 are the wrong types -- those types are specifically for integers, not for arbitrary data. Use e.g. MaybeUninit<u64> for arbitrary data of size 64 bits.
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Latest versions of rust will panic when trying to leave an uninitialized SerializedValue from mem::uninitialized which was breaking the js! macro