Include this file to get the `erase_from_memory` function that zeros memory. See https://www.cryptologie.net/article/419/zeroing-memory-compiler-optimizations-and-memset_s/

erase_from_memory.h

#ifndef __ERASE_FROM_MEMORY_H__
#define __ERASE_FROM_MEMORY_H__ 1

#define __STDC_WANT_LIB_EXT1__ 1
#include <stdlib.h>
#include <string.h>

void *erase_from_memory(void *pointer, size_t size_data, size_t size_to_remove) {
  #ifdef __STDC_LIB_EXT1__
   memset_s(pointer, size_data, 0, size_to_remove);
  #else
   if(size_to_remove > size_data) size_to_remove = size_data;
	 volatile unsigned char *p = pointer;
	 while (size_to_remove--){
		 *p++ = 0;
	 }
  #endif
	return pointer;
}

#endif // __ERASE_FROM_MEMORY_H__

test_erase.c

/*
gcc test_erase.c erase_from_memory.h
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "erase_from_memory.h"

int main(){
	char a[6] = "hello";
	printf("%s\n", a);
	erase_from_memory(a, 6, 6);
}