Error : Conflicting types for 'remove'

Question

I am getting an error "Conflicting types for 'remove'" at the line where I define my remove function. Most cases for this error occur whilst calling a function before its declaration. However, I'm making calls to my remove() in the main function, whilst having defined it beforehand. Then, why the error ?!?

    #include<stdio.h>
    #include<stdbool.h>

    struct node
    {
        int data;
        struct node* left;
        struct node* right;
    };

    struct node* newNode(int x)
    {
        struct node* temp=(struct node*)malloc(sizeof(struct node));
        temp->data=x;
        temp->left=NULL;
        temp->right=NULL;
        return temp;
    }

    struct node* insert(struct node* root,int x)
    {
        if (root==NULL)
            root=newNode(x);
        else if (x<=root->data)
            root->left=insert(root->left,x);
        else
            root->right=insert(root->right,x);
        return root;
    }

    struct node* remove(struct node* root,int x)
    {
        if (root==NULL)
            printf("Node not found !\n");
        else if (x==root->data)
        {
            struct node* temp=root;
            root=NULL;
            free(temp);
            printf("Node removed !\n");
        }
        else if (x<=root->data)
            root->left=remove(root->left,x);
        else
            root->right=remove(root->right,x);
        return root;
    }

    bool search(struct node* root,int x)
    {
        if (root==NULL)
            return false;
        else if (x==root->data)
            return true;
        else if (x<=root->data)
            return search(root->left,x);
        else
            return search(root->right,x);
    }

    void main()
    {
        struct node* root=NULL;
        root=insert(root,20);
        root=remove(root,10);
        root=insert(root,8);
        root=remove(root,10);
        root=insert(root,22);
        root=remove(root,22);
        root=insert(root,21);
        root=remove(root,10);
        root=insert(root,12);
        root=remove(root,12);
        root=insert(root,16);
        root=remove(root,10);
        root=insert(root,0);
        root=remove(root,10);
        root=insert(root,11);
        root=remove(root,10);
        root=remove(root,11);
        printf(search(root,10)?"Found\n":"Not Found\n");
        printf(search(root,20)?"Found\n":"Not Found\n");
        printf(search(root,11)?"Found\n":"Not Found\n");
        printf(search(root,17)?"Found\n":"Not Found\n");
    }

Answer 1

When compiling your code, I get this:

/tmp/x1.c:32: error: conflicting types for ‘remove’
/usr/include/stdio.h:154: error: previous declaration of ‘remove’ was here

As you can see, there is a function declared in stdio.h named remove. That conflicts with the definition you have.

You'll need to rename your function so it doesn't clash with the definition in stdio.h.