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19.4.3 Global Variables Replaced By Macros

All global variables in traditional flex have been replaced by macro equivalents.

Note that in the above example, yyout and yytext are not plain variables. These are macros that will expand to their equivalent lvalue. All of the familiar flex globals have been replaced by their macro equivalents. In particular, yytext, yyleng, yylineno, yyin, yyout, yyextra, yylval, and yylloc are macros. You may safely use these macros in actions as if they were plain variables. We only tell you this so you don’t expect to link to these variables externally. Currently, each macro expands to a member of an internal struct, e.g.,

#define yytext (((struct yyguts_t*)yyscanner)->yytext_r)

One important thing to remember about yytext and friends is that yytext is not a global variable in a reentrant scanner, you can not access it directly from outside an action or from other functions. You must use an accessor method, e.g., yyget_text, to accomplish this. (See below).