Dynamically-Scoped Attributes generate error(33): missing code generation template SetNonLocalAttrHeader ONLY in C++ target.

[Kameneth]

Target: c++
Generating parser code with ANTLR 4.13.0
Expected behavior: does not trigger any error .
Actual behavior: triggers an error(33): missing code generation template SetNonLocalAttrHeader

The DynScope grammar from the doc triggers the error. (from "Actions and Attributes" chapter, exactly as it is in it.)

antlr4 -Dlanguage=Java DynScope.g4 works

antlr4 -Dlanguage=PHP DynScope.g4 works

antlr4 -Dlanguage=JavaScript DynScope.g4 works

antlr4 -Dlanguage=Cpp DynScope.g4 does not work and generate the error(33).

Here is a simplified version of the grammar that triggers the same error:

grammar DynScope;
 
prog: block ;
 
block locals [int myInt = 0;]
	: '{' decl* '}' 
;

decl: 
  'int' INT {$block::myInt += 1;} ';'
;

INT : [0-9]+ ;
WS : [ \t\r\n]+ -> skip ;

if i just comment the {$block::myInt+=1;} ';', no errors is triggered.
like that:

grammar DynScope;
 
prog: block ;
 
block locals [int myInt = 0;]
	: '{' decl* '}' 
;

decl: 
  'int' INT // {$block::myInt += 1;} ';' 
;

INT : [0-9]+ ;
WS : [ \t\r\n]+ -> skip ;

replacing {$block::myInt += 1;} by {((BlockContext*)$ctx->parent)->myInt +=1 ;} seems to work properly.