'can't reference a struct pointer to function unless it has been previously allocated (and freed)

I supposed to write a long explanation of the code but the explanation is already in the code below so I guess my question is: How do I get it to work without having to malloc then freeing it? or basically what is the correct way to write this in a situation like this?

#include <stdio.h>
#include <malloc.h>

struct d {
    int f;
};

struct d* rr() {
    struct d* p = malloc(sizeof (struct d*));
    p->f = 33;
    return p;
}

void rr2(struct d* p) {
    p = malloc(sizeof (struct d*));
    p->f = 22;
}



int main()
{
    //works..
    struct d* g;
    g = malloc(sizeof (struct d));
    g->f = 45;
    printf("[%i]", g->f);
    
    //works..
    g = rr();
    printf("[%i]", g->f);
    

    //below, both are same, except in this first case, g is allocated then freed..
 
    //works..
    free(g);
    rr2(g);
    printf("[%i]", g->f);
    
    //doesn't work..
    struct d *q;
    rr2(q);
    printf("[%i]", q->f);



    return 0;
}

c pointers malloc pass-by-reference pass-by-value javascript html css

Solution 1:^[1]

.showcase {
    position: relative;
 }

Replace the 'position:absolute' property to 'position:relative' for above section. I will make your next section visible.

Solution 2:^[2]

--> Always use "Position:relation" on parent div after give "position:absolute" to child div.
--> i add "hero-section-wrapper" div for solve this issue & add some css for it.

 const menuToggle = document.querySelector('.toggle');
         const showcase = document.querySelector('.showcase');

         menuToggle.addEventListener('click', () => {
           menuToggle.classList.toggle('active');
           showcase.classList.toggle('active');
         })

    @import url('https://fonts.googleapis.com/css?family=Poppins:200,300,400,500,600,700,800,900&display=swap');
*
{
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Poppins', sans-serif;
}


.hero-section-wrapper {
    position: relative;
    height: 100vh;
    display: table;
    width: 100%;
}


header
{
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  padding: 40px 100px;
  z-index: 1000;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
header .logo
{
  color: #fff;
  text-transform: uppercase;
  cursor: pointer;
}
.toggle
{
  position: relative;
  width: 60px;
  height: 60px;
  background: url(https://i.ibb.co/HrfVRcx/menu.png);
  background-repeat: no-repeat;
  background-size: 30px;
  background-position: center;
  cursor: pointer;
}
.toggle.active
{
  background: url(https://i.ibb.co/rt3HybH/close.png);
  background-repeat: no-repeat;
  background-size: 25px;
  background-position: center;
  cursor: pointer;
}
.showcase
{
  position: absolute;
  right: 0;
  width: 100%;
  min-height: 100vh;
  padding: 100px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: #000000;
  transition: 0.5s;
  color: #ffff;
  z-index: 2;

}
.showcase.active
{
  right: 300px;
}



.showcase video
{
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  opacity: 0.8;
}
.overlay
{
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: #0394f4;
  mix-blend-mode: overlay;
  color: #001540;
}
.text
{
  position: relative;
  z-index: 10;
}

.text h2
{
  font-size: 2.5em;
  font-weight: 800;
  color: #fff;
  line-height: 1em;
  text-transform: uppercase;
}
.text h3
{
  font-size: 5em;
  font-weight: 700;
  color: #64A8F0;
  line-height: 1em;
  text-transform: uppercase;
}
.text p
{
  font-size: 1.1em;
  color: #fff;
  margin: 20px 0;
  font-weight: 400;
  max-width: 700px;
}
.text a
{
  display: inline-block;
  font-size: 1em;
  background: #fff;
  padding: 10px 30px;
  text-transform: uppercase;
  text-decoration: none;
  font-weight: 500;
  margin-top: 10px;
  color: #111;
  letter-spacing: 2px;
  transition: 0.2s;
}
.text a:hover
{
  letter-spacing: 6px;
}



.social
{
  position: absolute;
  z-index: 10;
  bottom: 20px;
  display: flex;
  justify-content: center;
  align-items: center;
}
.social li
{
  list-style: none;
}
.social li a
{
  display: inline-block;
  margin-right: 20px;
  filter: invert(1);
  transform: scale(0.5);
  transition: 0.5s;
}
.social li a:hover
{
  transform: scale(0.5) translateY(-15px);
}


.menu
{
  position: absolute;
  top: 0;
  right: 0;
  width: 300px;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: #000026;

}
.menu ul
{
  position: relative;
}
.menu ul li
{
  list-style: none;
}
.menu ul li a
{
  text-decoration: none;
  font-size: 24px;
  color: #ffff;
}
.menu ul li a:hover
{
  color: #64A8F0;
}



.section{
    width: 100%;
    min-height: 100vh;
    background-color: #ddd;
}
.container{
    width: 80%;
    display: block;
    margin:auto;
    padding-top: 100px;
}
.content-section{
    float: left;
    width: 55%;
}
.image-section{
    float: right;
    width: 40%;
}
.image-section img{
    width: 100%;
    height: auto;
}
.content-section .title{
    text-transform: uppercase;
    font-size: 28px;
}
.content-section .content h3{
    margin-top: 20px;
    color:#5d5d5d;
    font-size: 21px;
}
.content-section .content p{
    margin-top: 10px;
    font-family: sans-serif;
    font-size: 18px;
    line-height: 1.5;
}
.content-section .content .button{
    margin-top: 30px;
}
.content-section .content .button a{
    background-color: #3d3d3d;
    padding:12px 40px;
    text-decoration: none;
    color:#fff;
    font-size: 25px;
    letter-spacing: 1.5px;
}
.content-section .content .button a:hover{
    background-color: #a52a2a;
    color:#fff;
}
.content-section .social{
    margin: 40px 40px;
}
.content-section .social i{
    color:#a52a2a;
    font-size: 30px;
    padding:0px 10px;
}
.content-section .social i:hover{
    color:#3d3d3d;
}
@media screen and (max-width: 768px){
    .container{
    width: 80%;
    display: block;
    margin:auto;
    padding-top:50px;
}
.content-section{
    float:none;
    width:100%;
    display: block;
    margin:auto;
}
.image-section{
    float:none;
    width:100%;

}
.image-section img{
    width: 100%;
    height: auto;
    display: block;
    margin:auto;
}
.content-section .title{
    text-align: center;
    font-size: 19px;
}
.content-section .content .button{
    text-align: center;
}
.content-section .content .button a{
    padding:9px 30px;
}
.content-section .social{
    text-align: center;
}



@media (max-width: 991px)
{
  .showcase,
  .showcase header
  {
    padding: 40px;
  }
  .text h2
  {
    font-size: 1.5em;
  }
  .text h3
  {
    font-size: 3em;
  }

<div class="hero-section-wrapper">
    <section class="showcase">

       <header>
         <h2 class="logo"></h2>
         <div class="toggle"></div>
       </header>

       <video src="Video/video.mp4" muted loop autoplay></video>
       <div class="overlay"></div>
           <div class="text">
             <h2>Willkommen auf </h2>
             <h3>Think Tank</h3>
             <p>Beispiel.</p>
             <a href="#">THINK kaufen</a>
           </div>
           <ul class="social">
             <li><a href="#"><img src="https://i.ibb.co/x7P24fL/facebook.png"></a></li>
             <li><a href="https://twitter.com/ThinkTank__?t=RxrP3KIpS8-L6UOfjpd7Ww&s=08"><img src="https://i.ibb.co/Wnxq2Nq/twitter.png"></a></li>
             <li><a href="https://www.instagram.com/think.tank.official/"><img src="https://i.ibb.co/ySwtH4B/instagram.png"></a></li>
           </ul>
    </section>
    </div>
     <div class="menu">
       <ul>
         <li><a href="index.html">Home</a></li>
         <li><a href="section">Unser Token</a></li>
         <li><a href="#">NFT (COMING SOON)</a></li>
         <li><a href="#">Das Team</a></li>
         <li><a href="#">Kontakt</a></li>
       </ul>
     </div>


    <div class="section">
        <div class="container">
            <div class="content-section">
                <div class="title">
                    <h1>About Us</h1>
                </div>
                <div class="content">
                    <h3>Lorem ipsum dolor sit amet, consectetur adipisicing</h3>
                    <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
                    tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
                    quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
                    consequat.</p>
                    <div class="button">
                        <a href="">Read More</a>
                    </div>
                </div>
                <div class="social">
                    <a href=""><i class="fab fa-facebook-f"></i></a>
                    <a href=""><i class="fab fa-twitter"></i></a>
                    <a href=""><i class="fab fa-instagram"></i></a>
                </div>
            </div>
            <div class="image-section">
                <img src="https://images.unsplash.com/photo-1640525999004-42b645dd3dee?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=1170&q=80">
            </div>
        </div>
    </div>

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	mmd
Solution 2	Satish Modha

'can't reference a struct pointer to function unless it has been previously allocated (and freed)

Solution 1:[1]

Solution 2:[2]

Sources

Related Questions

Solution 1:^[1]

Solution 2:^[2]