Add minWidthBits for Type_Error

[usha1830]

No description provided.

[mihaibudiu]

I am afraid this does not conform to the spec

[usha1830]

I am afraid this does not conform to the spec

If we do not handle Type_Error here, it leads to an error "width not well-defined" while generating P4Info in certain cases.
Any suggestion on how we can fix this? Should we avoid calling this function minWidthBits() when the type is Type_Error?

[mihaibudiu]

That is my point, I belive that the spec days that it is an error to call this function on values of type error.

[mihaibudiu]

Why does the compiler call width on an error type?

[usha1830]

Why does the compiler call width on an error type?

In P4info, each table match key has a field for bitwidth. When an error type variable is used as match key field of a table, this function is called.

table parser_error {
    key = {
        istd.parser_error : exact;
    }
   // rest of the table properties
}

P4info:

match_fields {              
     id: 1                     
     name: "istd.parser_error" 
     bitwidth : 0
     match_type: EXACT         
   }   

From the P4Runtime spec (section 8.5.5),
"For enum types with no underlying type — as well as error — there is no integer value associated with each symbolic member entry (whether assigned automatically by the compiler or directly in the P4 source). We therefore use a human-readable string in P4Data to represent enum and error values."

As an error type does not have any underlying bitwidth (which is what the error is), I think we can treat the error type as a string.