mbbill / flexbison Goto Github PK

Sorry, if this is a dumb question. But the stmt part in fb3-2.y seems like ambiguous, but why does bison accept it?

stmt: IF exp THEN list           { $$ = newflow('I', $2, $4, NULL); }
   | IF exp THEN list ELSE list  { $$ = newflow('I', $2, $4, $6); }
   | WHILE exp DO list           { $$ = newflow('W', $2, $4, NULL); }
   | exp
;

$ make -f Makefile.ch9
flex -opurewc.lex.c purewc.l
cc -g -c -o purewc.lex.o purewc.lex.c
purewc.l:32:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
int argc;
^~~~
cc -g -o purewc purewc.lex.c
purewc.l:32:1: warning: return type defaults to ‘int’ [-Wimplicit-int]
int argc;
^~~~
flex -opurecalc.lex.c purecalc.l
bison -vd purecalc.y
cc -g -c -o purecalc.lex.o purecalc.lex.c
In file included from purecalc.l:14:0:
purecalc.tab.h:86:21: warning: ‘struct pcdata’ declared inside parameter list will not be visible outside of this definition or declaration
int yyparse (struct pcdata *pp);
^~~~~~
cc -g -c -o purecalc.tab.o purecalc.tab.c
purecalc.tab.c:143:21: warning: ‘struct pcdata’ declared inside parameter list will not be visible outside of this definition or declaration
int yyparse (struct pcdata *pp);
^~~~~~
purecalc.tab.c:1024:1: error: conflicting types for ‘yyparse’
yyparse (struct pcdata *pp)
^~~~~~~
purecalc.tab.c:143:5: note: previous declaration of ‘yyparse’ was here
int yyparse (struct pcdata *pp);
^~~~~~~
purecalc.tab.c: In function ‘yyparse’:
purecalc.tab.c:1193:16: error: too few arguments to function ‘yylex’
yychar = yylex (&yylval);
^~~~~
In file included from purecalc.y:26:0:
purecalc.lex.h:321:12: note: declared here
extern int yylex
^~~~~
: recipe for target 'purecalc.tab.o' failed
make: *** [purecalc.tab.o] Error 1
$ cc --version
cc (Debian 6.2.1-5) 6.2.1 20161124
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ flex --version
flex 2.6.1
$ bison --version
bison (GNU Bison) 3.0.4
Written by Robert Corbett and Richard Stallman.

Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.