include: co/error.h.

#co::error

1. int error();
2. void error(int e);

• 1, returns the current error code.
• 2, set the current error code to e.

#co::strerror

1. const char* strerror(int e);
2. const char* strerror();

• 1, get the description information of the error code e, thread-safe.
• 2, get the description information of the current error code, thread-safe.