demo.c: In function ‘calls_free’:                                              
demo.c:6:3: warning: double-free of ‘victim’ [CWE-415]                         
    6 |   free (victim);                                                       
      |   ^~~~~~~~~~~~~                                                        
cc1: note: summary of interprocedural path                                     
  ‘test’: events 1-2                                                           
     |                                                                         
     |   11 | void test (void *ptr)                                            
     |      |      ^~~~                                                        
     |      |      |                                                           
     |      |      (1) entry to ‘test’                                         
     |......                                                                   
     |   15 |   calls_free (ptr);                                              
     |      |   ~~~~~~~~~~~~~~~~                                               
     |      |   |                                                              
     |      |   (2) calling ‘calls_free’ from ‘test’                           
     |                                                                         
     +--> ‘calls_free’: events 3-4                                             
                |                                                              
                |    4 | calls_free (void *victim)                             
                |      | ^~~~~~~~~~                                            
                |      | |                                                     
                |      | (3) entry to ‘calls_free’                             
                |    5 | {                                                     
                |    6 |   free (victim);                                      
                |      |   ~~~~~~~~~~~~~                                       
                |      |   |                                                   
                |      |   (4) first ‘free’ here                               
                |                                                              
     <----------+                                                              
     |                                                                         
  ‘test’: events 5-6                                                           
     |                                                                         
     |   15 |   calls_free (ptr);                                              
     |      |   ^~~~~~~~~~~~~~~~                                               
     |      |   |                                                              
     |      |   (5) returning to ‘test’ from ‘calls_free’                      
     |......                                                                   
     |   19 |   calls_free (ptr);                                              
     |      |   ~~~~~~~~~~~~~~~~                                               
     |      |   |                                                              
     |      |   (6) calling ‘calls_free’ from ‘test’                           
     |                                                                         
     +--> ‘calls_free’: events 7-8                                             
                |                                                              
                |    4 | calls_free (void *victim)                             
                |      | ^~~~~~~~~~                                            
                |      | |                                                     
                |      | (7) entry to ‘calls_free’                             
                |    5 | {                                                     
                |    6 |   free (victim);                                      
                |      |   ~~~~~~~~~~~~~                                       
                |      |   |                                                   
                |      |   (8) second ‘free’ here                              
                |                                                              
demo.c: In function ‘test’:                                                    
demo.c:11:6: note: (1) entry to ‘test’                                         
   11 | void test (void *ptr)                                                  
      |      ^~~~                                                              
......
   15 |   calls_free (ptr);                                                    
      |   ~~~~~~~~~~~~~~~~                                                     
      |   |                                                                    
      |   (2) calling ‘calls_free’ from ‘test’                                 
demo.c: In function ‘calls_free’:                                              
demo.c:4:1: note: (3) entry to ‘calls_free’                                    
    4 | calls_free (void *victim)                                              
      | ^~~~~~~~~~                                                             
    5 | {
    6 |   free (victim);                                                       
      |   ~~~~~~~~~~~~~                                                        
      |   |                                                                    
      |   (4) first ‘free’ here                                                
demo.c: In function ‘test’:                                                    
demo.c:15:3: note: (5) returning to ‘test’ from ‘calls_free’                   
   15 |   calls_free (ptr);                                                    
      |   ^~~~~~~~~~~~~~~~                                                     
......
   19 |   calls_free (ptr);                                                    
      |   ~~~~~~~~~~~~~~~~                                                     
      |   |                                                                    
      |   (6) calling ‘calls_free’ from ‘test’                                 
demo.c: In function ‘calls_free’:                                              
demo.c:4:1: note: (7) entry to ‘calls_free’                                    
    4 | calls_free (void *victim)                                              
      | ^~~~~~~~~~                                                             
    5 | {
    6 |   free (victim);                                                       
      |   ~~~~~~~~~~~~~                                                        
      |   |                                                                    
      |   (8) second ‘free’ here