[#1362] Clarify that switch statements _are_ allowed in action/function bodies, and that switch statements with action_run expressions are only allowed in control apply blocks
#1363
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Signed-off-by: kfcripps <[email protected]>
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So this does work in the P4C, right? |
@vlstill For backends that don't run the |
| This type of `switch` statement can only be used within control `apply` | ||
| blocks. For this variant of `switch` statement, the expression must be | ||
| of the form `t.apply().action_run`, where `t` is the name of a table | ||
| (see <<sec-invoke-mau>>). All switch labels must be names of |
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Isn't this implicit from the fact that table.apply() can only be used in control apply blocks, not in functions or actions?
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"This type of switch statement can only be used within control apply blocks." is definitely implied by other parts of the spec, but it seems reasonable to say here, too.
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I also don't think it hurts to explicitly state that here, but if anyone strongly opposes it I can remove it.
The other clarifications are the most important parts of this PR.
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I can't merge, so feel free to merge if everyone is happy with the changes. |
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@jonathan-dilorenzo Discussed at 2025-Mar-10 and everyone that approves still approves, and ChrisDodd is good with the little bit of redundancy introduced as well. Please take a look, and merge if you also approve. As far as we know, p4c already supports this, although there are ongoing discussions on achieving good test coverage for different back ends that prefer different transformations for switch statements before the backend is reached. Those discussions only affect p4c test coverage, not the language of this spec change. |
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@kfcripps, can I ask you to add a bullet point summarizing the change to this section? https://p4.org/p4-spec/docs/p4-16-working-draft.html#_summary_of_changes_made_in_unreleased_version Happy to merge after that! |
…tory section Signed-off-by: Kyle Cripps <[email protected]>
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@jonathan-dilorenzo I realized that I did not add a bullet to this section in #1358, so I also added a bullet summarizing the changes made by #1358. |
p4-16/spec/P4-16-spec.adoc
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| @@ -9046,6 +9048,9 @@ The P4 compiler should provide: | |||
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| === Summary of changes made in unreleased version | |||
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| * Clarified that numeric priorities cannot be assigned to entries of a table that has `const entries` (<<sec-entries>>). | |||
| * Clarify that `switch` statements are allowed in action and function bodies, and that `switch` statements with `action_run` expressions are only allowed in control `apply` blocks (<<sec-stmts>> and <<sec-switch-stmt>>). | |||
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nit: clarified*
Let's stick to the same tense ;). O.w. LGTM
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Much obliged on both accounts! Thanks Kyle! |
Signed-off-by: Kyle Cripps <[email protected]>
Cleans up some wording that was missed by #945, which makes it unclear as to whether
switchstatements are actually supported in actions/functions or not.Closes #1362.