Derive Macro memflow_derive::Pod

source · 
#[derive(Pod)]
Expand description

Auto derive the Pod trait for structs.

The type is checked for requirements of the Pod trait:

  • Be annotated with repr(C) or repr(transparent).

  • Have every field’s type implement Pod itself.

  • Not have any padding between its fields.

Compile errors

Error reporting is not very ergonomic due to how errors are detected:

  • error[E0277]: the trait bound $TYPE: Pod is not satisfied

    The struct contains a field whose type does not implement Pod.

  • error[E0512]: cannot transmute between types of different sizes, or dependently-sized types

    This error means your struct has padding as its size is not equal to a byte array of length equal to the sum of the size of its fields.

  • error: no rules expected the token <

    The struct contains generic parameters which are not supported. It may still be possible to manually implement Pod but extra care should be taken to ensure its invariants are upheld.

Remarks:

This custom derive macro is required because the dataview proc macro searches for ::dataview::derive_pod!(). See https://github.com/CasualX/dataview/blob/master/derive_pod/lib.rs for the original implementation.