C Function Returning Pointers

C Function Returning Pointers

Like function return int, float, char, or any other data type, function can also return a pointer.

To return a pointer in function, needs to be explicitly mentioned in the calling function and also in function definition.

Function Returning A Pointer In C Program

This C program returns a pointer of local integer variable in the function but local variable (val) scope dies in calling function, so prints nothing.

#include <stdio.h>                                                          
                                                                                                                                        
// Function declaration.                                                                             
int *get_addr();                                                                
                                                                                
void main()                                                                     
{                                                                               
  int *addr;                                                                    
  addr = get_addr();                                                            
  printf("%u\n", addr);                                                         
  printf("%d\n", *addr);                                                        
}                                                                               
                        
// Function returning a pointer                                                        
int *get_addr()                                                                 
{                                                                               
  int val = 10;                                                          
  return &val;                                                                  
}    

$ cc function-return-pointers.c
function-return-pointers.c: In function ‘get_addr’:
function-return-pointers.c:16:10: warning: function returns address of local variable [-Wreturn-local-addr]
   return &val;
          ^~~~
$ ./a.out 
0
Segmentation fault (core dumped)

Making static

Make static to prevent val to be survived,

#include <stdio.h>                                                          
                                                                                                                                        
// Function declaration.                                                                             
int *get_addr();                                                                
                                                                                
void main()                                                                     
{                                                                               
  int *addr;                                                                    
  addr = get_addr();                                                            
  printf("%u\n", addr);                                                         
  printf("%d\n", *addr);                                                        
}                                                                               
                        
// Function returning a pointer                                                        
int *get_addr()                                                                 
{                                                                               
  static int val = 10;                                                          
  return &val;                                                                  
}    

$ cc function-return-pointers.c
$ ./a.out 
6295596
10