C -Segmentation fault ! - c

Question

It seems at least weird to me... The program runs normally.But after I call the enter() function for the 4th time,there is a segmentation fault!I would appreciate any help.
With the following function enter() I wanna add user commands' datas to a list.
[Some part of the code is already posted on another question of me, but I think I should post it again...as it's a different problem I'm facing now.]
/* struct for all the datas that user enters on file*/
typedef struct catalog
{ char short_name[50];
char surname[50];
signed int amount;
char description[1000];
struct catalog *next;
}catalog,*catalogPointer;
catalogPointer current;
catalogPointer head = NULL;
void enter(void) //user command: i <name> <surname> <amount> <description>
{
int n,j=2,k=0;
char temp[1500];
char *short_name,*surname,*description;
signed int amount;
char* params = strchr(command,' ') + 1; //strchr returns a pointer to the 1st space on the command.U want a pointer to the char right after that space.
strcpy(temp, params); //params is saved as temp.
char *curToken = strtok(temp," "); //strtok cuts 'temp' into strings between the spaces and saves them to 'curToken'
printf("temp is:%s \n",temp);
printf("\nWhat you entered for saving:\n");
for (n = 0; curToken; ++n) //until curToken ends:
{
if (curToken)
{ short_name = malloc(strlen(curToken) + 1);
strncpy(short_name, curToken, sizeof (short_name));
}
printf("Short Name: %s \n",short_name);
curToken = strtok(NULL," ");
if (curToken)
{ surname = malloc(strlen(curToken) + 1);
strncpy(surname, curToken,sizeof (surname)); }
printf("SurName: %s \n",surname);
curToken = strtok(NULL," ");
if (curToken)
{ //int * amount= malloc(sizeof (signed int *));
char *chk;
amount = (int) strtol(curToken, &chk, 10);
if (!isspace(*chk) && *chk != 0)
fprintf(stderr,"Warning: expected integer value for amount, received %s instead\n",curToken);
}
printf("Amount: %d \n",amount);
curToken = strtok(NULL,"\0");
if (curToken)
{ description = malloc(strlen(curToken) + 1);
strncpy(description, curToken, sizeof (description));
}
printf("Description: %s \n",description);
break;
}
if (findEntryExists(head, surname,short_name) != NULL) //call function in order to see if entry exists already on the catalog
printf("\nAn entry for <%s %s> is already in the catalog!\nNew entry not entered.\n",short_name,surname);
else
{
printf("\nTry to entry <%s %s %d %s> in the catalog list!\n",short_name,surname,amount,description);
newEntry(&head,short_name,surname,amount,description);
printf("\n**Entry done!**\n");
}
// Maintain the list in alphabetical order by surname.
}
catalogPointer findEntryExists (catalogPointer head, char num[],char first[])
{ catalogPointer p = head;
while (p != NULL && strcmp(p->surname, num) != 0 && strcmp(p->short_name,first) != 0)
{ p = p->next; }
return p;
}
catalogPointer newEntry (catalog** headRef,char short_name[], char surname[], signed int amount, char description[])
{
catalogPointer newNode = (catalogPointer)malloc(sizeof(catalog));
catalogPointer first;
catalogPointer second;
catalogPointer tmp;
first=head;
second=NULL;
strcpy(newNode->short_name, short_name);
strcpy(newNode->surname, surname);
newNode->amount=amount;
strcpy(newNode->description, description);
while (first!=NULL)
{ if (strcmp(surname,first->surname)>0)
second=first;
else if (strcmp(surname,first->surname)==0)
{
if (strcmp(short_name,first->short_name)>0)
second=first;
}
first=first->next;
}
if (second==NULL)
{ newNode->next=head;
head=newNode;
}
else //SEGMENTATION APPEARS WHEN IT GETS HERE!
{ tmp=second->next;
newNode->next=tmp;
first->next=newNode;
}
}
UPDATE:
SegFault appears only when it gets on the 'else' loop of InsertSort() function.
I observed that segmentation fault appears when i try to put on the list names that are after it.
For example, if in the list exists:
[Name:b Surname:b Amount:6 Description:b]
[Name:c Surname:c Amount:5 Description:c]
[Name:d Surname:d Amount:4 Description:d]
[Name:e Surname:e Amount:3 Description:e]
[Name:g Surname:g Amount:2 Description:g]
[Name:x Surname:x Amount:1 Description:x]
and i put: " x z 77 gege" there is a segmentation
but if i put "x a 77 gege" it continues normally....

Answer 1

Can't post into comment, so here it goes:
while (first!=NULL) { //-> this loop can exit ONLY with 'first' being NULL
if (strcmp(surname,first->surname)>0)
second=first;
else if (strcmp(surname,first->surname)==0) {
if (strcmp(short_name,first->short_name)>0)
second=first;
}
first=first->next;
}
if (second==NULL) {
newNode->next=head;
head=newNode;
}
else {
tmp=second->next;
newNode->next=tmp;
first->next=newNode; // first used (but it's NULL!)
}
In other words, your program will crash if it finds any entry that satisfy conditions inside the loop and set 'second'. (This triggers intended addition "inside" the list).
Ok ~ no time to wait for answer :o), in a case you want to enter "after" the 'second' change code to this:
if (second==NULL) {
newNode->next=head;
head=newNode;
}
else {
newNode->next=second->next;
second->next=newNode;
}
explanation (S is 'second', N a 'newNode', A B just some exisiting entries in the list):
initial:
N
A -> S -> B
first assignment:
N ---\
|
v
A -> S -> B
second assignment:
N ---\
^ |
| v
A -> S B
and thus:
A-> S -> N -> B

Answer 2

Not sure what's causing the bug, but I did see this bad pattern:
char *short_name;
short_name = malloc(strlen(curToken) + 1);
strncpy(short_name, curToken, sizeof (short_name));
sizeof(short_name) will be always the same thing (usually 4 for 32 bit platforms and 8 for 64 bit platforms) so is not the correct value to use here. You should be doing:
strncpy(short_name, curToken, strlen(curToken) + 1);

Answer 3

Use something like valgrind to find problems like this.

Answer 4

Falling out of your while loop requires first to be null. In the else statement you attempt to access first.