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我想创建一个基于 flex 的 CSS2.1 词法扫描器。w3 org上有扫描仪 flex 实现。我试着打电话

$ flex css2.1.flex
$ gcc lex.yy.c -lfl

但得到错误：

css2.1.flex: In function ‘yylex’:
css2.1.flex:53:9: error: ‘S’ undeclared (first use in this function)
css2.1.flex:53:9: note: each undeclared identifier is reported only once for each function it appears in
css2.1.flex:58:9: error: ‘CDO’ undeclared (first use in this function)
css2.1.flex:59:9: error: ‘CDC’ undeclared (first use in this function)
css2.1.flex:60:9: error: ‘INCLUDES’ undeclared (first use in this function)
css2.1.flex:61:9: error: ‘DASHMATCH’ undeclared (first use in this function)
css2.1.flex:63:9: error: ‘STRING’ undeclared (first use in this function)
css2.1.flex:64:9: error: ‘BAD_STRING’ undeclared (first use in this function)
css2.1.flex:66:9: error: ‘IDENT’ undeclared (first use in this function)
css2.1.flex:68:9: error: ‘HASH’ undeclared (first use in this function)
css2.1.flex:70:9: error: ‘IMPORT_SYM’ undeclared (first use in this function)
css2.1.flex:71:9: error: ‘PAGE_SYM’ undeclared (first use in this function)
css2.1.flex:72:9: error: ‘MEDIA_SYM’ undeclared (first use in this function)
css2.1.flex:73:9: error: ‘CHARSET_SYM’ undeclared (first use in this function)
css2.1.flex:75:9: error: ‘IMPORTANT_SYM’ undeclared (first use in this function)
css2.1.flex:77:9: error: ‘EMS’ undeclared (first use in this function)
css2.1.flex:78:9: error: ‘EXS’ undeclared (first use in this function)
css2.1.flex:79:9: error: ‘LENGTH’ undeclared (first use in this function)
css2.1.flex:85:9: error: ‘ANGLE’ undeclared (first use in this function)
css2.1.flex:88:9: error: ‘TIME’ undeclared (first use in this function)
css2.1.flex:90:9: error: ‘FREQ’ undeclared (first use in this function)
css2.1.flex:92:9: error: ‘DIMENSION’ undeclared (first use in this function)
css2.1.flex:94:9: error: ‘PERCENTAGE’ undeclared (first use in this function)
css2.1.flex:95:9: error: ‘NUMBER’ undeclared (first use in this function)
css2.1.flex:97:9: error: ‘URI’ undeclared (first use in this function)
css2.1.flex:99:9: error: ‘BAD_URI’ undeclared (first use in this function)
css2.1.flex:101:9: error: ‘FUNCTION’ undeclared (first use in this function)

我必须如何声明缺少的标识符？

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1 回答 1

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它们是在链接上的 flex 语法之前的解析器定义中定义的。当你bison -d在解析器定义上运行类似的东西时，它会生成一个y.tab.h包含定义的文件（通常是 ）。

于 2012-07-02T09:00:02.963 回答