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

    
void str_cpy (char **a,   const char *  b) {
   char * tmp = NULL;
   int size_str = strlen(b)+1;
  
   tmp = realloc(tmp, size_str);
   memmove (tmp, b, size_str);
   free (*a);
   *a = tmp;
}


void str_cat (char **a,  const char *b){
   int size_str_1 = strlen(b);
   int size_str_2 = strlen(*a);
  
   *a = realloc(*a, size_str_1 + size_str_2 + 1);
   memmove (*a + size_str_2, b, size_str_1 + 1);
}

int main() {
   char *s = NULL;

   str_cpy(&s, "Hola Mola");    
   str_cpy(&s, s+5);    
   str_cat(&s," World");
      
   return 0;
}

static void foo(char *str)
{
    printf("%p\n", str);
}

int main(void)
{
    foo(NULL);
    foo("\0");
    return 0;
}

'\0'

"\0"

void foo(char *str) {
    printf("%s \n", str );
}

int main(void) {
    foo(NULL);
    foo('\0');
    foo(0);
    
    return 0;
}

stdout:
(null)
(null)
(null)

/*
* Copyright (C) 2002     Manuel Novoa III
* Copyright (C) 2000-2005 Erik Andersen <andersen@uclibc.org>
*
* Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
*/

#include "_string.h"

#ifdef WANT_WIDE
# define Wstrlen wcslen
#else
# define Wstrlen strlen
#endif

size_t Wstrlen(const Wchar *s)
{
    register const Wchar *p;

    for (p=s; *p; p++);

    return p - s;
}
libc_hidden_weak(Wstrlen)

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

    
void str_cpy ( char **a, const char * b ) {

   int size_src;
   char overlap;
  
   if ( b ) size_src = strlen( b ) + 1; else return;
   overlap = (*a <= b && *a + size_src >= b) || (b <= *a && b + size_src >= *a);
   *a = realloc( *a, size_src );
   if ( overlap )  
      for (*a += size_src, b += size_src; size_src--; *--*a = *--b);
   else
       memcpy( *a, b, size_src );
}


void str_cat ( char **a,  const char *b ){
   int size_src, size_des;
      
   if ( *a ) size_des = strlen( *a ); else size_des = 0;
   if ( b )  size_src = strlen( b ); else return;
  
   *a = realloc( *a, size_src + size_des + 1 );
   memmove ( *a + size_des, b, size_src + 1 );
}

int main() {
   char *s = NULL;
  
   str_cpy( &s, "Hola Mola" );    
   str_cpy( &s, s+5 );      
   str_cat( &s," World" );  
  
   return 0;
}