Hi Anand,
the problem is in your productions of "external_declaration".
Informally: Imagine the shift-reduce parser generated by bison sees one
of the following terminals as the next symbol in the input: STATIC,
CONST, VOLATILE, EXTERN, INT or UNSIGNED. The parser now can reduce the
init_dec rule, as one of the aforementioned terminals is expected after
init_dec according to the productions of declaration, but the machine
could also be shifting the terminal as instructed by the production of
function_definition.
If you are not familiar with the way the shift-reduce parser operates,
have a look e.g. at wiki. If you get how the machine operates, the
output from bison --verbose will hopefully make sense to you.
Cheers, Alex
On 07/31/2010 03:54 PM, anandvn wrote:
>
> Hi,
>
> Could any one please help me in resolving the shift/reduce in the following
> grammar?
>
> %{
> #include <stdio.h>
> extern char yytext[];
> extern int column;
> void yyerror(char const *s);
> %}
>
> %union
> {
> unsigned int tokVal;
> unsigned char *tokValStr;
> }
>
> /* C operators */
> %token <tokVal> STATIC CONST VOLATILE EXTERN INT UNSIGNED VARNAME EQUAL
> COLON OP_BRACE CL_BRACE IDENTIFIER
>
> %type <tokVal> declaration translation_unit declaration_specifiers
> storage_class_specifier type_specifier type_qualifier init_declarator_list
>
> /* Parsing starts with this transalation unit */
> %start translation_unit
>
> %%
>
> translation_unit
> : external_declaration
> | translation_unit external_declaration
> ;
>
> external_declaration
> : function_definition
> | declaration
> ;
>
> function_definition
> : declaration_specifiers declarator compound_statement
> ;
>
> declarator
> : IDENTIFIER
> ;
>
> compound_statement
> : OP_BRACE CL_BRACE
> ;
>
> declaration
> : init_dec declaration_specifiers COLON
> | init_dec declaration_specifiers init_declarator_list COLON
> ;
>
> init_dec
> : {printf("*** Process for Initialization ***\n\n");}
>
> init_declarator_list
> : EQUAL VARNAME
> ;
>
> declaration_specifiers
> : storage_class_specifier
> | storage_class_specifier declaration_specifiers
> | type_specifier
> | type_specifier declaration_specifiers
> | type_qualifier
> | type_qualifier declaration_specifiers
> ;
>
> storage_class_specifier
> : EXTERN
> | STATIC
> ;
>
> type_specifier
> : INT
> | UNSIGNED
> ;
>
> type_qualifier
> : CONST
> | VOLATILE
> ;
>
> %%
>
> void yyerror(char const *s)
> {
> fflush(stdout);
> printf("\n%*s\n%*s\n", column, "^", column, s);
> }
>
> In the rule "declaration", I want to perform initalization activities using
> the empty rule "init_dec" (original code here
> http://old.nabble.com/file/p29313133/Test.zip Test.zip ). But i'm getting
> shift/reduce conflict. Since I'm new to this bison, i need help from you to
> resolve this conflict. I tried by i felt very difficult.
>
> Thanks
> Anand V
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