LDWG meeting minutes, November 4, 2019

Attendees

• Mihai Budiu (VMware)
• Chris Dodd (Barefoot)
• Andy Fingerhut (Cisco)
• Nate Foster (Cornell)
• Vladimir Gurevich (Barefoot)
• Jed Liu (Barefoot)
• Jeremias Lindine (Barefoot)
• Gordon Brebner
• Antonin Bas

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Status

• We released v1.2.0!

• Working style

• Some time dealing with bigger issues
• Some time discussing larger issues

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Varbits

Summary

• Gordon Brebner introduced a use case where a varbit might support a setSize(int<N>) operation.

References

• https://github.com/p4lang/p4-spec/issues/264

Discussion

• We observed that Section 8.8 of the specification already allows assignment between varbits.

• Does this work with P4 Runtime? Antonin says not now, but soon.

Action Item

• Andy Fingerhut or Mihai Budiu will race to see who can do it first.

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Structure of Annotations

Summary

• P4_16 v1.2.0 removed structure from annotations, which means that other tools need to do extra parsing.

References

• https://github.com/p4lang/p4-spec/issues/789/

Status

• Nate Foster proposed some additional syntax for annotations that would enable giving structure:

@annot(...)
@annot{...}
@annot[...]

Discussion

• There may be issues with parsing the second form for block structures (e.g., controls)

Action Item

• Develop an implementation in the compiler.

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Structure-valued Expressions

• Proposes to add a new kind of expression that evaluates to a struct.

• https://github.com/p4lang/p4-spec/pull/773

Status

Discussion

• We discussed ambiguity that can arise with structs and possible ways of disambiguating.

Action Item

• Comment on pull request

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Abstract Methods

• Proposes to add abstract methods.

• https://github.com/p4lang/p4-spec/pull/

Status

Discussion

• Based on Domino paper from SIGCOMM

Action Item

• Read pull request and makes comments.

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Next Meeting

• Mihai to discuss module system