在gram.c 中，有一行：#define yyparse  base_yyparse

看gram.y 中，与此对应的是： %name-prefix="base_yy"

而看 bison 的 manual:

4.1 The Parser Function yyparse

You call the function yyparse to cause parsing to occur. This function reads tokens, executes actions, and ultimately returns when it encounters end-of-input or an unrecoverable syntax error. You can also write an action which directs yyparse to return immediately without reading further.

— Function: int 

yyparse (

void)

The value returned by yyparse is 0 if parsing was successful (return is due to end-of-input).

The value is 1 if parsing failed because of invalid input, i.e., input that contains a syntax error or that causes YYABORT to be invoked.

The value is 2 if parsing failed due to memory exhaustion.