混合Bison和C代码

Question

Here is part of my program.

    %{
    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    #include <math.h>
    int yylex(void);
    int yylineno;
    char* yytext;
    void yyerror(const char *s) { printf("ERROR: %s\n", s); }
    void addID(char *ID);

%}

%union{ char * string;}


%%
    program: 
|DECLARE vdeclarations IN commands END
;

vdeclarations:
vdeclarations IDENTIFIER {addID($2);}
| IDENTIFIER {addID($1);}
;

and some C functions at the end

    struct list_ID {
    char *ID;
    int index;
    struct list_ID * next;
};
typedef struct list_ID list_ID;
list_ID * curr, * head;
head = NULL;
int i = 0;
void addID(char *s)
{
    curr = (list_ID *)malloc(sizeof(list_ID));
    curr->ID = strdup(s);
    curr->index = i++;
    free(s);
    curr->next = head;
    head = curr;
}

I simply want to add all IDENTIFIERS to linked list but gcc give me such errors.

kompilator.y:74:1: warning: data definition has no type or storage class [enable
d by default]
kompilator.y:74:1: error: conflicting types for 'head'
kompilator.y:73:19: note: previous declaration of 'head' was here
kompilator.y:74:8: warning: initialization makes integer from pointer without a
cast [enabled by default]
kompilator.y: In function 'addID':
kompilator.y:82:13: warning: assignment makes pointer from integer without a cas
t [enabled by default]
kompilator.y:83:7: warning: assignment makes integer from pointer without a cast
 [enabled by default]

so isnt it possible to make such mixs in bison ? or there is something wrong with my C code part?

Answer 1

head = NULL; 

This is a statement outside of any function. This is not allowed.

If you want to initialize global data, do it at the point of declaration:

list_ID * curr, * head = NULL;

In addition, you should not cast the result of malloc . Make sure you have zero warnings while compiling with -Wall -Wextra.