no matching function for call to 'number::number(void)'-CodePudding

Hello I'm trying to code a linked list but it's not working. Malloc at first and at last pointers is returning a no matching function for call to. Here's the code:

#include <stdio.h>
#include <stdlib.h>
    
    typedef struct number{
        int x;
        struct number *next;
    }Number;
        
    Number *first = NULL, *temp = NULL, *last = NULL;
    
    void insert(int x){
    
        if(first==NULL){
            
            first= (Number)malloc(sizeof(Number));
            first->x=x;
            first->next = NULL;
            temp=first;
        }
        else{
            last = (Number)malloc(sizeof(Number));
            last->x = x;
            last->next = NULL;
            temp->next =last;
            temp=last;
        }
        
    
    }
    
    void printList(){
        Number *hold = first;
        
        while(hold!=NULL){
            printf("\n%d\n",hold->x);
            hold = hold->next;
        }
    }
    
    
    int main(){
        
        int size;
        printf("Enter size: ");
        scanf("%d",&size);
        Number *hold = first;
        
        printf("Enter value:\n");
        
        
        
        for(int i=0;i<size;i  ){
            int x;
            scanf("%d",&x);
            insert(x);
        }
        
        printfList();
    }

what could be wrong here?

CodePudding user response：

Your "insert" logic ("append", actually) is wonky. Regions are allocated, but the addresses returned are soon lost.

void insert( int x ) {
    temp = malloc( sizeof *temp ); // Make a node
    /* omitting test for NULL */

    temp->x = x; // populate its members
    temp->next = NULL;

    if( first == NULL )
        first = temp; // all done!
    else
        last = last->next =  temp; // all done here, too!
}

CodePudding user response：

the problem is that you declared first to be a pointer in that line

Number *first = NULL, *temp = NULL, *last = NULL;

but when you are trying to use malloc, malloc returns a pointer of type void, so you should cast it into (Number*) not (Number), you should cast void pointer into Number pointer.

so instead of

first = (Number)malloc(sizeof(Number));

you should do

first = (Number*)malloc(sizeof(Number));

refer to malloc() manual as the prototype of malloc is

void *malloc(size_t size);

and just one small syntax error, it's not

printfList();

it's :

printList();

with these small edits, this is the final code:

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

typedef struct number{
    int x;
    struct number *next;
}Number;

Number *first = NULL, *temp = NULL, *last = NULL;

void insert(int x){

    if(first==NULL){

        first = (Number*)malloc(sizeof(Number));
        first->x=x;
        first->next = NULL;
        temp=first;
    }
    else{
        last = (Number*)malloc(sizeof(Number));
        last->x = x;
        last->next = NULL;
        temp->next =last;
        temp=last;
    }


}

void printList(){
    Number *hold = first;

    while(hold!=NULL){
        printf("\n%d\n",hold->x);
        hold = hold->next;
    }
}


int main(){

    int size;
    printf("Enter size: ");
    scanf("%d",&size);

    printf("Enter value:\n");



    for(int i=0;i<size;i  ){
        int x;
        scanf("%d",&x);
        insert(x);
    }

    printList();
}

and this is some example output:

Enter size:5
 Enter value:
1
2
3
4
5

1

2

3

4

5

CodePudding user response：

The error message sounds you like are compiling this with a c instead of a c compiler.
Number is a typedef for struct Number but you use it as a pointer. In c, we don't cast void pointers so just leave it out:

void insert(int x) {
    if(first==NULL){
        first = malloc(sizeof(Number));
        first->x=x;
        first->next = NULL;
        temp = first;
    } else {
        last = malloc(sizeof(Number));
        last->x = x;
        last->next = NULL;
        temp->next = last;
        temp = last;
    }
}

printfList() should be printList().

and here is an example execution:

Enter size: 3
Enter value:
1
2
3

1

2

3

I suggest you eliminate the global variables and pass them into the functions that need them. temp, in particular, is a implementation detail of insert().
Also, the inconsistent formatting, means that I instantly distrust your code. Formatting matters for readability so why make it hard for yourself?