使用 memcpy 将 int 转换为 union/struct 类型

Question

I am new to the programming world.

int a = 10;
typedef union {
  struct {
    int a1;
    ....
    ...
  }
  unsigned int b1;
} type_union;

type_union *ptr = (type_union *)&a;

This typecast is not conventional it seems. Can you suggest how can I use memcpy to do the same.

Answer 1

OP comments giving a misra 11.3 error .

[MISRA 2012 Rule 11.3, required]: A cast shall not be performed between a pointer to object type and a pointer to a different object type.

The alignment requirements of an int and union may differ (example: union needs may exceed int ) so...

type_union *ptr = (type_union *)&a;  // Bad

... risks undefined behavior (UB).

Instead, create an object of type type_union and copy the data. memcpy() is not used to cast , but to copy.

type_union obj; 
obj.tbd.a1 = a;  // tbd as OP's source lacks a member name,
// or 
memcpy(&obj, &a, sizeof a);