Thread: Two "equivalent" functions

I made an attempt to shorten my code in a particular function because it had lines that repeated themselves.

The function that has duplicate lines but works

Code:

static Line newLines (char text[]) {
    Line list = NULL, curr;
	int lineCount = 1;
	int length = strlen(text);
	int subLength;
	int i=0, prevPos = i;
	
	if (*text == '\0')
	    return NULL;
	
	list = malloc(sizeof(struct line));
	if (list == NULL)
	    memoryError();
	    
    curr = list;
	
	for (; i<length; i++) {
	    if (text[i] == '\n') {
            //line text:
	        subLength = i-prevPos+1; //+1 = null terminator
            curr->text = malloc(sizeof(char)*subLength);
            if (curr->text == NULL)
                memoryError();
	        strncpy(curr->text, &text[prevPos], subLength);
	        curr->text[subLength-1] = '\0';
	        //line number:
	        curr->lineNum = lineCount;
	        //next line:
	        curr->next = malloc(sizeof(struct line));
	        if (curr->next == NULL)
	            memoryError();
	        
	        curr = curr->next;
	        prevPos = i+1;
	        lineCount++;
        }
	}
	
    //line text:
    subLength = i-prevPos+1;
    curr->text = malloc(sizeof(char)*subLength);
    if (curr->text == NULL)
        memoryError();
    strncpy(curr->text, &text[prevPos], subLength);
	//line number:
    curr->lineNum = lineCount;
    //next line:
    curr->next = NULL;

    return list;
}

Notice that the first few lines in the for loop are equivalent to the bottom of the function.

Now, this is what I did to try and simplify things:

Code:

static Line newLines (char text[]) {
    Line list = NULL, curr;
	int lineCount = 1;
	int length = strlen(text);
	int subLength;
	int i=0, prevPos = i;
	
	if (*text == '\0')
	    return NULL;
	
	list = malloc(sizeof(struct line));
	if (list == NULL)
	    memoryError();
	    
    curr = list;
	
	for (; i<=length; i++) {
	    if (text[i] == '\n' || text[i] == '\0') {
	    printf("text[i] = %c\n", text[i]);
            //line text:
            subLength = i-prevPos+1; // +1 = null terminator
            curr->text = malloc(sizeof(char)*subLength);
            if (curr->text == NULL)
                memoryError();
            strncpy(curr->text, &text[prevPos], subLength);
	        //line number:
            curr->lineNum = lineCount;
            
	        //next line:
            if (text[i] == '\n') {
	            curr->next = malloc(sizeof(struct line));
	            if (curr->next == NULL)
	                memoryError();
	            
	            curr = curr->next;
	            prevPos = i+1;
	            lineCount++;
            } else
                curr->next = NULL;
        }
	}

    return list;
}

And I just cannot figure out why it doesn't work. It works fine for single line text (no \n chars) but gives me some crazy memory error for multiple line text.

Could someone please give me a little insight into this?

It would help if you told us what that crazy memory error was. It would also help if we had some more code, so we could actually compile and test this ourselves. Last crucial thing would be the input you provide to the program, the (incorrect) output you get if any, and the expected (correct) output.

This line seems to be missing from your new version:

Code:

curr->text[subLength-1] = '\0';

EDIT: I did it the hard way, just by reading. Try using a diff tool if your system has one, or something like Diff Checker - Online diff tool to find the difference between two text files, to find the difference between two pieces of text.

The missing line that you pointed out was the problem... That's pretty embarrassing haha

That diff tool is a good idea. Thanks!