Discuss adding namespace to P4-16 spec

[hesingh]

Problem statement is here.

1. This would mean, a base headers file must enclose all P4 code in one or more namespace(s).
2. namespace is added as a new reserved keyword to P4-16. Syntax is same as in C++, namespace M {}
3. If the compiler processes an include file using namespace M, and processes other P4 code with same namespace, does the compiler raise an error or just adds a new M_1 namespace to reference map?
4. The compiler find routines will add find object in specific namespace.

[apinski-cavium]

#798
#718
#628
#77
#37
All are related.

[hesingh]

@apinski-cavium thanks,

Andy Fingerhut's doc in this issue has replaced module in #798 by namespace.

P4 already supports #include and all P4 needs to add is namespace to meet the goals in Andy's doc mentioned in this issue. So what use case needs Python import?

[hesingh]

I assumed Andy's doc mentioned in this issue has captured thoughts from any modularity discussion. Since his doc did not include a solution, I filed this issue.

Second, my company has already addressed @vgurevich goals in #798 using two new keywords in P4 - override and super. See the "Quick testing..." section at this link: https://github.com/hesingh/mnkcg/tree/master/p4-ansible

Having read other issues, I am with Andy regarding using namespace which is not the C++ namespace per se. If Name Mangling is used there is no conflict between included code and code in a new P4 program. Right now, with P4-16, I can define several controls in file1.p4 and call the controls in file2.p4 just fine because file2.p4 includes file1.p4. So, why bother with P4 parser and control for Modularity?

So now the only problem to solve is how to use import module in P4?