I use a public library. It change its struct from struct aaa to struct x\_aaa in newer version.
I want to keep my code pass compiling in any version of the library.
So I want to do such:

```
#if lib_ver > 20000
typedef struct x_aaa struct aaa;
#endif

```

And then use strcut aaa in later code. But this not work. How do you solve such problem?