Making YACC output an AST (token tree)

%{


typedef struct tree_t {
    struct tree_t **links;
    int nb_links;
    char* type; // the grammar rule
};


#define YYDEBUG 1
//int yydebug = 1;


tree_t *_C_treeRoot;
%}
%union tree_t


%start program


%token IDENTIFIER
%token CONSTANT


%left '+' '-'
%left '*' '/'
%right '^'


%%
progam: exprs { _C_treeRoot = &$1.t; }
    |
    | hack
    ;


exprs:
    expr ';'
    | exprs expr ';'
    ;




number:
    IDENTIFIER
    | '-' IDENTIFIER
    | CONSTANT
    | '-' CONSTANT
    ;


expr:
    number
    | '(' expr ')'
    | expr '+' expr
    | expr '-' expr
    | expr '*' expr
    | expr '/' expr
    | expr '^' expr
    ;


hack:
    {
    // called at each reduction in YYDEBUG mode
    #undef YY_SYMBOL_PRINT
    #define YY_SYMBOL_PRINT(A,B,C,D) \
        do { \
            int n = yyr2[yyn]; \
            int i; \
            yyval.t.nb_links = n; \
            yyval.t.links = malloc(sizeof *yyval.t.links * yyval.t.nb_links);\
            yyval.t.str = NULL; \
            yyval.t.type = yytname[yyr1[yyn]]; \
            for (i = 0; i < n; i++) { \
              yyval.t.links[i] = malloc(sizeof (YYSTYPE)); \
              memcpy(yyval.t.links[i], &yyvsp[(i + 1) - n], sizeof(YYSTYPE)); \
            } \
        } while (0)


    }
    ;
%%


#include "lexer.c"




int yyerror(char *s) {
    printf("ERROR : %s [ligne %d]\n",s, num_ligne);
    return 0;
}




int doParse(char *buffer)
{
    mon_yybuffer = buffer;
    tmp_buffer_ptr = buffer;
    tree_t *_C_treeRoot = NULL;
    num_ligne = 1;
    mon_yyptr = 0;
    return !yyparse();
}




char *tokenStrings[300] = {NULL};
char *charTokenStrings[512];


void initYaccTokenStrings()
{
    int k;
    for (k = 0; k < 256; k++)
    {
        charTokenStrings[2*k] = (char)k;
        charTokenStrings[2*k+1] = 0;
        tokenStrings[k] = &charTokenStrings[2*k];
    }
    tokenStrings[CONSTANT] = "CONSTANT";
    tokenStrings[IDENTIFIER] = "IDENTIFIER";




    extern char space_string[256];


    for (k = 0; k < 256; k++)
    {
        space_string[k] = ' ';
    }
}