Call protected type method in declarative region
Capability
Currently the LRM disallows calling a method of a protected type in a declarative region.
However, in testing, many simulators already allow this.
Current Use Model
In the OSVVM AlertLogPkg, there is a singleton data structure. It is used control messaging and tabulate errors from particular message sources. Each message source is referenced by an ID. IDs are acquired when a model is created.
Currently we must do the following:
signal ModelID : AlertLogType ;
. . .
initialize : process
begin
ModelID <= GetAlertLogID("AxiStreamTx_1"); Updated Use Model
constant ModelID : AlertLogType := GetAlertLogID("AxiStreamTx_1"); GetAlertLogID is defined as follows and calls a method of a protected type.
package body AlertLogPkg is
type AlertLogStructPType is protected
. . .
type AlertLogStructPType is protected body
. . .
end protected AlertLogStructPType ;
shared variable AlertLogStruct : AlertLogStructPType ;
impure function GetAlertLogID(Name : string ; ParentID : AlertLogIDType := ALERTLOG_ID_NOT_ASSIGNED ; CreateHierarchy : Boolean := TRUE) return AlertLogIDType is
variable result : AlertLogIDType ;
begin
result := AlertLogStruct.GetAlertLogID(Name, ParentID, CreateHierarchy ) ;
return result ;
end function GetAlertLogID ;The benefits are more than just code compactness. The benefit is that now the IDs can be used during initialization (time 0 ns, simulation cycle 0).
Currently there is a growing number of similar use cases that can benefit from this.
LRM Edits
In 14.4.1, in the last paragraph, delete the text marked below:
In certain cases, the elaboration of a declarative item involves the evaluation of expressions that appear within the declarative item. The value of any object denoted by a primary in such an expression shall be defined at the time the primary is read (see 6.5.2). In addition, if a primary in such an expression is a function call, then the value of any object denoted by or appearing as a part of an actual designator in the function call shall be defined at the time the expression is evaluated. Additionally, it is an error if a primary that denotes a shared variable, or a method of the protected type of a shared variable, is evaluated during the elaboration of a declarative item. During static elaboration, the function STD.STANDARD.NOW (see 16.3) returns the value 0 ns.