c++ multi pthread pass struct

#include <stdio.h>
#include <stdlib.h>
#include <uuid/uuid.h>
#include <unistd.h>
#include <fstream>
#include <istream>
#include <ostream>
#include <sstream>
#include <string.h>
#include <iostream>
#include <chrono>

void retrieveUuid(char *uuidValue)
{
    uuid_t newUUID;
    uuid_generate(newUUID);
    uuid_unparse(newUUID, uuidValue);
}


void *printBookStruct(void *structP);
void mp12();

int main()
{
    mp12();
    return 0;
}

void mp12()
{
    struct BookStruct arr[100];
    for (int i = 0; i < 100; i++)
    {
        arr[i].BookId = i * i * i * i;
        arr[i].BookName = (char *)malloc(40);
        arr[i].BookTitle = (char *)malloc(40);
        retrieveUuid(arr[i].BookName);
        retrieveUuid(arr[i].BookTitle);
    }

    pthread_t tds[100];
    struct BookStruct *p;
    for(int i=0;i<100;i++)
    {    
        cout<<"Thread "<<i<<",started!";      
        pthread_create(&tds[i],NULL,printBookStruct,(void*)&arr[i]);
        pthread_join(tds[i],NULL);
        cout<<"Thread "<<i<<" finished!"<<endl;
    }

 pthread_exit(NULL);

}

void *printBookStruct(void *structP)
{
    struct BookStruct *p;
    p=(struct BookStruct*)(structP);
    if(p!=nullptr)
    {
        printf("BookId=%d,Name=%s,Title=%s!",p->BookId,p->BookName,p->BookTitle);
        free(p->BookName);
        free(p->BookTitle);
    } 
     pthread_exit(NULL);
}

Compile via g++ as below command

g++ -g -std=c++2a -I. h1.cpp -o h1 -luuid -lpthread

Run the complile result as below

./h1

The executed result as below

The keylocated at the invoked method. should modified by void * AKS void pointer method and the parameter should convert to void pointer and in the method should convert the void pointer to specific pointer

pthread_create(&tds[i],NULL,printBookStruct,(void*)&arr[i]);

void *printBookStruct(void *structP)
{
    struct BookStruct *p;
    p=(struct BookStruct*)(structP);
    if(p!=nullptr)
    {
        printf("BookId=%d,Name=%s,Title=%s!",p->BookId,p->BookName,p->BookTitle);
        free(p->BookName);
        free(p->BookTitle);
    } 
    pthread_exit(NULL);
    return nullptr;
}