malloc參數(shù)為0

winway1988

1. $ cat test.c
   
2. #include        <stdio.h>
   
3. 
   
4. int
   
5. main(void)
   
6. {
   
7.         char    *ptr = NULL;
   
8.         ptr = (char *)malloc(0);
   
9. 
   
10.         printf("ptr = %p\n", ptr);
    
11. 
    
12.         printf("*ptr = %c\n", *ptr);
    
13.         *ptr = 'a';
    
14.         printf("*ptr = %c\n", *ptr);
    
15. 
    
16.         free(ptr);
    
17.         ptr = NULL;
    
18. 
    
19.         return 0;
    
20. }

復(fù)制代碼

1. $ ./a.out
   
2. ptr = 0x3988010
   
3. *ptr =
   
4. *ptr = a

復(fù)制代碼

這個(gè)該怎么解釋？
上網(wǎng)只搜到這句話，"even a request for zero bytes returns a pointer to something of the minimum allocatable size."

liuiang

1. man malloc
   
2. ...
   
3. If size is 0, then malloc() returns either NULL, or a unique pointer value that can later be successfully passed to free().
   
4. ...

復(fù)制代碼