akeep/p4-proposals

Collaboration space for working on in-progress proposals with a smaller team.

p4-proposals's Issues

Related p4c and p4-spec issues about converting enum to/from bit-vector types

I don't know how far any progress might be on this issue, but wanted to leave a pointer to it on this repo's issue, for reference.

p4lang/p4-spec#394

error is like enum, but might need separate explicit mention to include it in serializable

It has slightly different syntax for adding new error codes, and unlike enum has no 'type name' -- there is only one 'error enum' in any P4_16 program as specified now, but anyone can add more values to it anywhere at the top level of the program, or multiple places later.

One use case for making it serializable is to pass the value to the control plane in a header of a packet that experienced a parser error. Not a capability everyone would want in their P4 programs, but some may.

Minor nit - I don't think bool is actually serializable in current P4_16 spec

Summary: I believe that bool is currently in the same boat as enum as far as serializability goes, with 0 distinctions in what you can do with them.

This comment is prompted by this sentence in Section 3 of the serializable types proposal: "Currently, some scalar types (like bool types) are not explicitly serializable unless they are included as part of a header in the current spec"

bool is defined to have a way to cast a value of that type to bit<1>, or from bit<1> to bool.

Including either of them in a header is an error for the latest p4test and p4c-bm2-ss open source compilers.

I believe it is not allowed by the P4_16 v1.0.0 spec, either.