Thread: Varibale scope and memory allocation

Hi guys, I'm working on a school project right now for theory of language. I'm a C newbie and I encountered a problem that I can't seem to solve.

Any way, let me give you some background on the project. I'm suppose to implement a language generator from a given set of grammar.

I have my lexical analyzer working that spits out tokens. The next step is, I'm constructing the grammar as a form of link-list/arrays.

Here are my data structures

Code:

struct token{
	// Terminal or Non-Terminal
	int type;
	// If it is a non terminal, then it is the name, else, it is the content
	char *content_ptr;
	
	// The node is non-terminal, node_ptr points to an array of nodes below the current node.
	struct token_array *aptr;
};

struct token_array{
	int num_of_elements;
	struct token *tptr;
};

If the data strucutre is built correctly, it should look something like this

token_array ->an array of tokens
each token then points to NULL if it is a terminal or another token_array that points to more tokens in an array (non terminals).

And here is the code in trouble,

Code:

struct token_array build(FILE *file){

	int first_token=TRUE;
	
	char *char_ptr;
	
	struct token token_ptr;
	
	struct token_array grammar = {0, NULL};
	struct token_array temp_token_array = {0, NULL};
	
	do{
		char_ptr = next_token(file);
	
		if(char_ptr!=NULL){
			token_ptr = *token_wrapper(char_ptr);
			
			if(char_ptr[0]=='\n'){
				first_token=TRUE;
				grammar.tptr[grammar.num_of_elements-1].aptr = &temp_token_array;
				temp_token_array.num_of_elements=0;
				temp_token_array.tptr=NULL;
			}
			else{		
				if(first_token==TRUE){
					first_token=FALSE;
					
					grammar.num_of_elements++;
					grammar.tptr=realloc(grammar.tptr, grammar.num_of_elements*sizeof(struct token));
					grammar.tptr[grammar.num_of_elements-1]=token_ptr;
					
				}
				else{
					temp_token_array.num_of_elements++;
					temp_token_array.tptr=realloc(temp_token_array.tptr, temp_token_array.num_of_elements*sizeof(struct token));
					temp_token_array.tptr[temp_token_array.num_of_elements-1]=token_ptr;
				}
			}
								   	
			printf("%s\n", char_ptr);
		}
	}while(char_ptr!=NULL); 
	
	print_grammar(grammar);
	
	return grammar;
}

the main function look somethins like this....

Code:

   	grammar = build(file);
    	
    	printf("-------Grammar--------");
    	print_grammar(grammar);

The main problem is, when use printf, it destroyes the data structure. I get random values. If I do printf within the build function then everything is fine.

I think it have to do with the scope of the variable....
But I really is cruless

Thanks in advance for any help you can provide!