Clang的Lexer(词法分析器)的源码的主要位置如下:
clang/lib/Lex 这里是主要的Lexer的代码;
clang/include/clang/Lex 这里是Lexer的头文件代码的位置;
同时,Lexer还使用了clangBasic库,所以要分析Lexer的代码,clangBasic(clang/lib/Basic)的一些代码也会用到。
首先从Lexer入手。
clang/include/clang/Lex/Lexer.h
clang::Lexer:
00057 //===--------------------------------------------------------------------===// 00058 // Context-specific lexing flags set by the preprocessor. 00059 // 00060 00061 /// ExtendedTokenMode - The lexer can optionally keep comments and whitespace 00062 /// and return them as tokens. This is used for -C and -CC modes, and 00063 /// whitespace preservation can be useful for some clients that want to lex 00064 /// the file in raw mode and get every character from the file. 00065 /// 00066 /// When this is set to 2 it returns comments and whitespace. When set to 1 00067 /// it returns comments, when it is set to 0 it returns normal tokens only. 00068 unsigned char ExtendedTokenMode; 00069 00070 //===--------------------------------------------------------------------===//
这个成员变量保存词法分析的一个状态,根据它的值的不同:0、1、2,分别对应只返回正常的token,返回comments
和正常的token,返回空格、comments和正常的token。
下面是几个操作这个成员变量的函数,基本上都是获取值、设置值和重设值。代码不复杂,
00162 /// isKeepWhitespaceMode - Return true if the lexer should return tokens for 00163 /// every character in the file, including whitespace and comments. This 00164 /// should only be used in raw mode, as the preprocessor is not prepared to 00165 /// deal with the excess tokens. 00166 bool isKeepWhitespaceMode() const { 00167 return ExtendedTokenMode > 1; 00168 } 00169 00170 /// SetKeepWhitespaceMode - This method lets clients enable or disable 00171 /// whitespace retention mode. 00172 void SetKeepWhitespaceMode(bool Val) { 00173 assert((!Val || LexingRawMode || LangOpts.TraditionalCPP) && 00174 "Can only retain whitespace in raw mode or -traditional-cpp"); 00175 ExtendedTokenMode = Val ? 2 : 0; 00176 } 00177 00178 /// inKeepCommentMode - Return true if the lexer should return comments as 00179 /// tokens. 00180 bool inKeepCommentMode() const { 00181 return ExtendedTokenMode > 0; 00182 } 00183 00184 /// SetCommentRetentionMode - Change the comment retention mode of the lexer 00185 /// to the specified mode. This is really only useful when lexing in raw 00186 /// mode, because otherwise the lexer needs to manage this. 00187 void SetCommentRetentionState(bool Mode) { 00188 assert(!isKeepWhitespaceMode() && 00189 "Can‘t play with comment retention state when retaining whitespace"); 00190 ExtendedTokenMode = Mode ? 1 : 0; 00191 } 00192 00193 /// Sets the extended token mode back to its initial value, according to the 00194 /// language options and preprocessor. This controls whether the lexer 00195 /// produces comment and whitespace tokens. 00196 /// 00197 /// This requires the lexer to have an associated preprocessor. A standalone 00198 /// lexer has nothing to reset to. 00199 void resetExtendedTokenMode();
关于raw mode:
raw mode的时候,ExtendedTokenMode = 2,Lexer会输出包含空格、comments和正常tokens在内的所有
字符。在Lexer的父类:clang::PreprocessorLexer类中(clang/include/clang/Lex/PreprocessorLexer.h),有一个成员变量:
00049 /// \brief True if in raw mode. 00050 /// 00051 /// Raw mode disables interpretation of tokens and is a far faster mode to 00052 /// lex in than non-raw-mode. This flag: 00053 /// 1. If EOF of the current lexer is found, the include stack isn‘t popped. 00054 /// 2. Identifier information is not looked up for identifier tokens. As an 00055 /// effect of this, implicit macro expansion is naturally disabled. 00056 /// 3. "#" tokens at the start of a line are treated as normal tokens, not 00057 /// implicitly transformed by the lexer. 00058 /// 4. All diagnostic messages are disabled. 00059 /// 5. No callbacks are made into the preprocessor. 00060 /// 00061 /// Note that in raw mode that the PP pointer may be null. 00062 bool LexingRawMode;
它可以表明Lexer是否在raw mode下。同时,这里的注释也说明了raw model的作用。
时间: 2024-10-11 06:40:12