Simple linked list implementation in C.

linkedList.c

#include <stdio.h>
#include <stdlib.h>

typedef struct elementT {
  unsigned value;
  struct elementT *next;
} elementT;

elementT *removeElement(elementT *, unsigned);
elementT *addElement(elementT *, unsigned);
void printList(elementT *);

int main(void) {
  elementT *list = NULL;
#if TEST
  printf("Setup some elements\n");

  list = addElement(list, 0xdeadbeef);
  list = addElement(list, 0xcafef00d);
  list = addElement(list, 0x11111111);
  list = addElement(list, 0x00000000);
  list = addElement(list, 0xfeedface);

  printf("List:\n");
  printList(list);
  printf("\n");

  printf("Remove some elements\n");
  printf("0xfeedface\n");
  list = removeElement(list, 0xfeedface);
  printf("List:\n");
  printList(list);
  printf("\n");

  printf("0x11111111\n");
  list = removeElement(list, 0x11111111);
  printf("List:\n");
  printList(list);
  printf("\n");

  printf("0xdeadbeef\n");
  list = removeElement(list, 0xdeadbeef);
  printf("List:\n");
  printList(list);
  printf("\n");

#endif
  return 0;
}

elementT *removeElement(elementT *l, unsigned v) {
  if(l == NULL) {
    /* you're trying to remove something from an empty list */
    return l;
  }
  else {
    elementT *t = l;
    elementT *p = NULL;
    do {
      if(t->value == v) {
	if(t != l) {
	  p->next = t->next;
	  free(t);
	  return l;
	}
	else {
	  elementT *u = t->next;
	  free(t);
	  return u;
	}
      }
      p = t;
      t = t->next;
    } while(t != NULL);
  }
  /* couldn't find it */
  return l;
}

elementT *addElement(elementT *l, unsigned v) {
  elementT *t = (elementT *)calloc(sizeof(elementT), 1);
  t->value = v;
  t->next = NULL;
  if(l == NULL) {
    return t;
  }
  else {
    elementT *u = l;
    while(u->next != NULL)
      u = u->next;
    u->next = t;
    return l;
  }
}

void printList(elementT *l) {
  for(;l != NULL;l = l->next) {
    printf("%p: 0x%08x\n", (void *)l, l->value);
  }
}

i've used calloc to make sure that the pointer it NULL on creation. i'm sure theres some weird different between mac and linux with malloc.
also, if i don't cast i get compiler warnings (-Wall -Wextra -pedantic) about types, technically next is (struct elementT *) ;)

You assign the next pointer to NULL 2 lines down. If you have c++-compat on it will complain if you do:
something = malloc(); so you should use something = (elementT *) malloc();

But no gcc switches should complain about the casting ..... ooooh you've got an un-named struct:
typedef struct { } elementT;
should be:
typedef struct elementT { } elementT;

void printList(elementT *l) {
for(;l != NULL;l = l->next) {
printf("%p: 0x%08x\n", (void *)l, l->value);
}
}
}

The last return in removeElement should probably be return NULL; otherwise you don't know the difference between a match and a failure.

cheers moyers.
the last point shouldn't matter for what i need it for, however, if i were to do that i'd lose the whole list?

Yeaaah you would. Usually with this kind of list you pass in an "elementT **list" to all your functions so that the list pointer can be modified.

Actually if you don't find the element you're searching for then you can guarantee that your input list was not modified so you can safely use the list pointer you passed in.

ahh, pointer pointer is how it would be do, the reason i'm returning is because i'm an idiot and forgot about that. sending a null pointer to the newElement function doesn't do anything when you try to create a new element and set the pointer. because its the functions scope which gets set rather than whats passed in. meh, this works for what i need it to (i think). i just need to modify the simulator code. still have a weird unknown segfault under certain circumstances on 32bit :S

…

On 27 Jan 2012, at 19:30, iamscottmoyers wrote: Yeaaah you would. Usually with this kind of list you pass in an "elementT **list" to all your functions so that the list pointer can be modified. Actually if you don't find the element you're searching for then you can guarantee that your input list was not modified so you can safely use the list pointer you passed in. --- Reply to this email directly or view it on GitHub: https://gist.github.com/1689809