c - 我的 C 语法存在许多多重选择错误

Question

我正在尝试使用 Antlwork 编写 C 语法，为此我使用了这个 http://stuff.mit.edu/afs/athena/software/antlr_v3.2/examples-v3/java/C/C.g我试图通过删除许多我不使用的 block 和回溯来使其变得更简单。这就是我所拥有的:http://www.archive-host.com/files/1956778/24fe084677d7655eb57ba66e1864081450017dd9/CNew.txt

然后，当我执行 ctrl+D 时，我收到很多警告和错误，如下所示:

[21:20:54] warning(200): C:\CNew.g:188:2:  Decision can match input such as "'{' '}'" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
[21:20:54] warning(200): C:\CNew.g:210:2: Decision can match input such as "'for' '('" using multiple alternatives: 2, 3
As a result, alternative(s) 3 were disabled for that input
[21:20:54] error(201): C:\CNew.g:210:2: The following alternatives can never be matched: 3

[21:20:54] error(208): C:\CNew.g:250:1: The following token definitions can never be matched because prior tokens match the same input: CHAR

我真的不明白为什么我会收到所有这些警告，不应该有冲突。

Answer 1

but I still have this error

[22:02:55] error(208): C:\Users\Seiya\Desktop\projets\TRAD\Gram\CNew.g:238:1: The following token definitions can never be matched because prior tokens match the same input: CONSTANT [22:17:18] error(208): CNew.g:251:1: The following token definitions can never be matched because prior tokens match the same input: CHAR [22:17:18] error(208): C:\Users\Seiya\Desktop\projets\TRAD\Gram\CNew.g:251:1: The following token definitions can never be matched because prior tokens match the same input: CHAR

这意味着词法分析器永远无法创建标记 CHAR 和 INT，因为其他一些词法分析器规则 CONSTANT 与相同的输入匹配。您需要做的是将 CONSTANT 更改为解析器规则。

换句话说，改变这两条规则:

primary_expression
    : ID
    | CONSTANT
    | '(' expression ')'
    ;

CONSTANT
    :   INT
    |   CHAR
    ;

分为以下内容:

primary_expression
    : ID
    | constant
    | '(' expression ')'
    ;

constant
    :   INT
    |   CHAR
    ;