2.7. C Language Cross-Reference

The final example in this chapter takes all the techniques we’ve learned so far and uses them in one program, a fairly realistic C language cross-referencer (Example 2-5). It uses nested input files to handle #include statements, start states to handle includes and comments, a lexical hack to track when a mention of a symbol is a definition rather than a reference, and a symbol table to keep track of it all.

Example 2-5. C cross-referencer

/* fb2-5 C cross-ref */
%option noyywrap nodefault yylineno

%x COMMENT
%x IFILE

/* some complex named patterns */
/* Universal Character Name */
UCN     (\\u[0-9a-fA-F]{4}|\\U[0-9a-fA-F]{8})
/* float exponent */
EXP     ([Ee][-+]?[0-9]+)
/* integer length */
ILEN    ([Uu](L|l|LL|ll)?|(L|l|LL|ll)[Uu]?)