Embedded development knowledge summary

offsetof macro and container_of

Offsetof macro action: calculating an offset relative to the first address of an element in the structure structure

The role of macro container_of: Pointer know the structure of a member variable, pointer thrust reverser structure variables

#include <stdio.h>
 #define the offsetof (type, Member) ((int) & ((type *) 0) -> Member)
 #define container_of (PTR, type, Member) ({\
     const  typeof (((type *) 0 ) -> Member) * the mptr = (PTR); \ 
    (type *) (( char *) the mptr - the offsetof (type, Member));})
 // action typeof keyword: typeof (a) by the obtaining a variable a variable type 
typedef struct Node {
     int a;
     Double B;
     a float C; 
} N1; 
int main () 
{ 
    N1 S; 
    a float * P = & (SC); 
    the printf ("offsetof(c) = %d\n",offsetof(n1,c));
    printf("addr of s is %p\n",&s);
    printf("container_of(p,n1,c) = %p\n",container_of(p,n1,c));
    return 0;
    
}

the sizeof ( Short ) = 2 
the sizeof ( int ) = . 4 
the sizeof ( Long ) = . 4
 
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the After the Exited Process 0.1803 seconds The with return value 0 
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