使用antlr和line指令的C ++代码插入 [英] C++ Code insertion using antlr and the line directive

问题描述

我正在使用antlr将自定义语言转换为C ++代码. 用这种语言，用户可以在$code...$endcode指令之间嵌入C ++代码段，这些指令原样插入到翻译后的C ++代码中.

I am using antlr to translate a custom language to C++ code. In this language, user can embed C++ code snippets between $code...$endcode directives, that gets inserted into the translated C++code as-is.

我有以下问题:当代码片段中有错误时，我希望编译器指向源文件，而不是指向翻译后的C ++代码.

I have the following problem: When there is an error in the code snippet I would like the compiler to point to the source file rather than the translated C++ code.

我尝试如下使用行指令，但是没有用:

I tried using line directives as follows, but it didn't work:

"foo.custom_laguage"
1 $code
2 ...some c++ code...
3 $endcode

获取翻译为

"auto-generated.cpp"
42 #line 2 "foo.custom_language"
43 ...some c++ code...
44 #line __LINE__ __FILE__

这不起作用，我认为是因为#line指令会修改稍后由__LINE__宏写入的内容.如何在翻译后的C ++代码中将行号设置回 actual 行号? antlr如何做到这一点?

This doesn't work, I think because #line directive modifies what gets written by the __LINE__ macro later. How can I set line number back to the actual line number in the translated C++ code? How does antlr do this?

这是我想要自动生成的代码的样子:

Here is what I want the auto-generated code to look like:

"auto-generated.cpp"
42 #line 2 "foo.custom_language"
43 ...some c++ code...
44 #line 44 "auto-generated.cpp"  //actual line in this file
45 ..some more C++ code ...

编辑:我刚刚发现有一种方法可以通过使用#line default指令以C#语言实现: http://msdn.microsoft.com/en-us/library/34dk387t.aspx 但是找不到与C ++类似的东西

edit: I just found out that there is a way to do this in C# language by using a #line default directive: http://msdn.microsoft.com/en-us/library/34dk387t.aspx But couldn't find anything similar for C++

推荐答案

这个问题尚不清楚，但是您是自己给source-line和source-file生成#line指令的吗?对不起，我对Antlr不熟悉.

It's not clear from the question, but you're generating the #line directives yourself given source-line and source-file? I'm sorry, I'm not familiar with Antlr.

实际上，#line __LINE__ __FILE__除了将__LINE__宏分配给自身外，什么也不做.

Indeed, #line __LINE__ __FILE__ does nothing but assign the __LINE__ macro to itself.

由于预处理器的评估语义，您不能轻松地将__LINE__的数值分配给宏. (您只能定义一个新的宏以字面意义映射到__LINE__宏，并返回其 current 值.)但是，为什么需要这样做呢?除非Antlr本身使用__LINE__宏，否则您无需将其还原为以前的值.

Because of the evaluation semantics of the preprocessor, you can't easily assign the numeric value of __LINE__ to a macro. (You can only define a new macro to map to the macro __LINE__ literally, returning its current value.) But why do you need that? Unless Antlr itself uses the __LINE__ macro, you don't need to restore it to its previous value.

如果遇到问题，最直接的解决方案是将原始C ++代码放入单独的include文件中，并放弃内联嵌入.为了防止头文件扩散，您可以使用类似

If it is an issue, the most straightforward solution would be to put the raw C++ code in separate include files and forgo the inline embedding. To prevent proliferation of header files, you could use a construct like

$code
#define USE_SNIPPET_FOO
#include "snippets.h"
$endcode

$code
#define USE_SNIPPET_BAR
#include "snippets.h"
$endcode

在标头中，还有一种反向标头保护:

and in the header, a kind of reverse header guard:

#ifdef USE_SNIPPET_FOO
#undef USE_SNIPPET_FOO
class foo {};

#elif defined USE_SNIPPET_BAR
#undef USE_SNIPPET_BAR
class bar {};

#else
#error no snippet selected
#endif

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