如何在xtext DSL中嵌入C ++代码？(How to embed C++ code in a xtext DSL?)

 在Xtext / ANTLR中处理C ++代码块的正确方法是什么？ 
 
 我们正在为DSL编写一个基于Xtext的eclipse插件，支持在明确定义的范围（大多数是serial { /* ... */ }块）中添加C ++功能级代码，例如： 
 
module m {
  chare c {
    entry void foo() {
      serial {
        // C++ code block
      }
    }
  }
}
 
 请参阅此处以获取更全面的示例。 然后将其移交给外部工具以处理进一步的编译/链接步骤，因此我们不会从eclipse生成任何代码。 
 
 这里的问题是如何处理这些C ++代码块，特别是考虑到它们可能包含自己的大括号。 这与如何在Xtext DSL中包含Java代码块非常相似？ 但是现在我们满足于忽略那个块（即没有内容辅助或语法突出显示不理想但可以接受。） 
 
 在我们的基于bison / flex的工具中，这是通过在解析器和词法分析器之间共享一个变量来完成的，该变量在某些语法规则中切换“C ++解析模式”，这使得词法分析器为除了相关分隔符（例如大括号）之外的所有内容返回CPROGRAM标记。 ）自然翻译似乎有一个自定义的ANTLR词法分析器，它使用语义谓词来达到同样的效果，例如 
 
RULE_NON_BRACES: {in_braces}? ~('{' | '}')+;
 
 作为第一个lexing规则，但是我找不到如何从Xtext语法中访问该全局变量，因为在bison中似乎没有“规则操作”的概念。 还有其他非“串行”语法上下文，其中需要C ++代码，因此需要在解析器和词法分析器之间进行一些协调。 

What is the proper way of handling C++ code blocks in Xtext/ANTLR?
 
We are writing an Xtext-based eclipse plugin for a DSL that supports adding C++ function-level code within well-defined scopes (mostly serial { /* ... */ } blocks) such as this:
 
module m {
  chare c {
    entry void foo() {
      serial {
        // C++ code block
      }
    }
  }
}
 
See here for a more comprehensive example. This is then handed over to an external tool to handle further compilation/linking steps, so we don't generate any code from eclipse.
 
The issue here is how to handle these C++ code blocks, especially given that they may contain braces of their own. This is very similar to How to include Java Code Block in Xtext DSL? but for now we are content with just ignoring that block (i.e. not having content assist or syntax highlighting is not ideal but acceptable.)
 
In our bison/flex-based tool this is done by sharing a variable between the parser and lexer that toggles a "C++ parsing mode" within certain grammar rules that makes the lexer return a CPROGRAM token for everything except the relevant delimiters (e.g. braces.) The natural translation seems to have a custom ANTLR lexer that uses semantic predicates to the same effect, e.g.
 
RULE_NON_BRACES: {in_braces}? ~('{' | '}')+;
 
as the first lexing rule, but I cannot find how to access that global variable from the Xtext grammar since there doesn't seem to be a concept of "rule action" as in bison. There are other non-"serial" grammar contexts where C++ code is expected, so there needs to be some coordination between the parser and lexer.

原文：https://stackoverflow.com/questions/35806402