Compiler Bug : Null firstCall

[robotrobo]

The following program crashes when trying to inline two controls and one of the controls is being called in an action.

p4test --Wdisable control_apply_action.p4.txt
In file: p4c/frontends/p4/inlining.cpp:521                                                
Compiler Bug: p4c/frontends/p4/inlining.cpp:521: Null firstCall      

control_apply_action.p4.txt

I'm filing this on behalf of @fruffy

[mihaibudiu]

We should probably forbid control invocation in actions if the invoked control contains any tables.

[jafingerhut]

The P4_16 language spec, appendix F, the last of the tables in that appendix: https://p4.org/p4-spec/docs/P4-16-v1.2.1.html#sec-calling-restrictions

has restricted that controls cannot be applied from within actions ever since that section was added a few years ago. I remember I initially had proposed allowing actions calling controls if the control did not invoke any tables, but I think you, Mihai, recommended against it then, I thought in general, and hence that is why that table has "no" for that entry.

Note: I am not here arguing for generalizing what is in the spec at this time. It seems perfectly reasonable if p4c follows what the spec says, and forbids calling controls from within action bodies, regardless of whether the control has tables or not.