how to access the member num of struct bio_st in openSSL-1.1.1

Question

in OpenSSL-1.1.1, struct bio_st is made opaque. To access the member of struct, APIs are provided. But I do not find an API to access the member int num of this struct.

in my application code with openSSL-1.0.2

fd_set fds;
FD_ZERO( &fds );
FD_SET( b->num, &fds );

for this now I get

error: dereferencing pointer to incomplete type 'BIO {aka struct bio_st}' FD_SET( b->num, &fds );

Does anyone have any idea?

Answer 1

Use the macro BIO_get_fd to get this.