Advanced Compiler HW#03

Homework 3: What are the so-called "action table" and "goto table" of GCC? (Hint: Try to find them in c-parse.c.) 

The "action table" and "goto table" of a typical LR parser are combined into a single table in GCC -- yytable.
Positive numbers in the table are used for shift action; negative numbers are used for reduce action; and 0, together with the most negative number, is used to indicate errors.

In c-parse.c, yyn = yytable[yyn];
Comments are listed below:
/* yyn is what to do for this token type in this state.
     Negative => reduce, -yyn is rule number.
     Positive => shift, yyn is new state.
     New state is final state => don't bother to shift, just return success.
     0, or most negative number => error.  */

Related source files:
int yyparse (YYPARSE_PARAM_ARG) //[c-parse.c]
static const short yytable[] = {...} //[c-parse.c] (a long one)
static const short yytable[] = {...} //[gengtype-yacc.c] (a short one)