Thread: malloc and calloc

Would someone explain to me how to use these? I keep getting a segmentation fault on this line:

Code:

strcpy(lines[e++] = calloc(l + 1, l + 1), storeline);

lines is a pointer array, storeline is a character string, l is the length of storeline, and my whole calloc expression is a pointer to space of the same size as storeline(at least that's what I'm going for).

As I understand it right now, the first parameter of calloc is the number of elements in an array(storeline) and the second parameter is the number of bytes of the memory block which is the same since 1 char = 1 byte?

If someone would show me how to use these functions I'd really appreciate it. Thanks.

The first is the number of members, and the second is the size of one member.

Thank you both.

I'm still getting a segmentation fault. This time in the strcpy line.

Code:

	while (l = getline(storeline, MAXLEN))
	{
		lines[e] = calloc(l + 1, 1);
		strcpy(lines[e++], storeline);
	}

This block is at the top of my program. The only thing above it is some error checking for argv. e is initialized at zero and here are my arrays:

Code:

	char *lines[MAXLINES];
	char storeline[MAXLEN];

Thanks again.

Does e go past MAXLINES? And is getline your own creation, since it doesn't seem to be the GNU version? If so, does it properly null-terminate things?

Yeah that's my version of getline and it does terminate the string. e does go past MAXLINES though.

Program received signal SIGSEGV, Segmentation fault.
0x08048648 in main (argc=2, argv=0xbffff4f4) at exercise.5-13.c:56
56 strcpy(lines[e++], storeline);
(gdb) print e
$1 = 134556832

Yeah thanks guys. So it turns out my getline function was returning length + 1 the whole time so my while loop never finished and that's why e was so high. For now I just removed the "+ 1" from my calloc expression and it worked like a charm. But now I can't for the life of me figure out why my getline function seems to be counting 1 more than it's supposed to. I'm sure it's something very simple and I'm just too much of a noob to see it but I bet you guys will see it quickly! Here it is:

Code:

int getline(char *s, int lim)
{
    int i = 0;
    
    for (s; --lim > 0 && (*s=getchar()) != EOF && *s != '\n'; ++s)
        ++i;

    if (*s == '\n')
	++i;
    ++s;
    *s = '\0';
    return i;
}

Spoke to soon. I tested the first line out of the loop and it worked. When I use the loop without the "+ 1" in the calloc parameter I still get a segmentation fault in my strcpy line. I'll get back to you.

Originally Posted by MK27

Probably because strcpy() appends a '\0', and you did not count that in getline(). It is normal, for example, to use strlen(s)+1 in a malloc() call since strlen() will not count the '\0' either.

Thank you but I ahve already accounted for this.

Turns out my input file had more lines than my MAXLINES. Can't believe I overlooked especially considering someone tried to point that out to me! Anyway, sorry for the confusion and thanks for the help.