Cannot find definition of 'ib_lock_t' in mysql server source code

Question

I read source code here: link of mysql source code

But after I searched the whole repository, I cannot find the defination of ib_lock_t.

search link: https://github.com/mysql/mysql-server/search?utf8=%E2%9C%93&q=ib_lock_t

search result:

Where is it defined?

Answer 1

Found: https://github.com/mysql/mysql-server/blob/a2757a60a7527407d08115e44e889a25f22c96c6/storage/innobase/include/lock0priv.h

Line: 110

I am still confused with the preprocess:

#define lock_t ib_lock_t.

Why to replace lock_t

without no definition of ib_lock_t?