Why is this code is not wrong?

[Virus.V]

When I use uGFX, I do not know how to get the "content change event" or "focus event" of the "txtedit" object, for example, when the object is focused, execute some code to display the virtual keyboard.
So I read uGFX source code trying to achieve this function, but I encountered a little problem.

In the "gevent.h" file on the 66th line, there is such a code:

typedef struct GSource_t GSource, * GSourceHandle;

I did not find the structure named GSource_t where the definition, but the compiler can be, can also run, why?

I think this code should be equivalent to the following code:

typedef struct GSource_t{} GSource, * GSourceHandle;

Is this right?

[inmarket]

That line is a "forward definition" and therefore is NOT equivalent to your suggested code. It is (in C++ terms) an abstract object not a reference to an empty structure.