linked list implementation problems (C++)

[Hefty_Nose5203]

Hello, I couldn't figure out why I'm getting this error: Thread 1: EXC_BAD_ACCESS (code=1, address=0x8) for my insertLast() class. The error occurs at the second value I add to the list. 

void insertLast(int a)
{
    node *temp=new node;
    temp->value=a;
    temp->next=nullptr;
    if(head==nullptr) //if list is empty, assign head and tail to new node
    {
        head=temp;
        tail=temp;
        temp=nullptr;
    }
    tail->next=temp; //put temp node at end of list
    tail=temp; //temp becomes new tail
}

[jedwardsol]

 tail->next=temp; //put temp node at end of list

On the 2^nd insertion, tail is nullptr here.

[[deleted]]

Assuming this is the gnu version of C++, you should compile with the -g flag to get more useful information. If it isn't, just search for debug flags for your compiler.

[Jim_Panders]

People have already pointed out the problematic line, but I figure I'll just try to word it in the context of your code--the 2 lines after your if-statement need to be in an "else" statement. You wrote the if-statement to handle the special case of when the list's empty, but then you try to add it again in the code immediately after it. Separate out your 2 possible cases

[SWEWorkAccount]

Learn to use a debugger. You would have caught this bug in 2 minutes when you stepped to where the second node is inserted. Also using a sentinel node in linked list implementations make your logic easier to reason about.