[SOLVED] C typedef can't understand

[saur]

Can anyone help me, as to what the following code snipped means?

typedef void (*XilExceptionHandler) (void *data);

 

[debabrta kar]

typedef facility allows us to define a new nam for an existing data type...... here in the above expression When this exception handler function is called, the parameter Data pointer contains the same value as you provided when you registered the handler.

 

[FvM]

Typedef of a function pointer.

 

[saur]

Hi debabrta kar
Thanks for the reply.

In the example code: they are using the data type XilExceptionHandler for a value Handler.

So does it mean the Handler contains void data as the Data pointer points to a void type??

Thanks
Saurabh

 

[FvM]

A void pointer can be casted to any pointer type. It's used to keep the referenced data type open.

 

[saur]

In the code snippet

 typedef void (*XilExceptionHandler) (void *data);

the XilExceptionHandler has been defined as a pointer to function which takes a void pointer a input parameter and returns nothing, according to what I've understood. Pls correct me if I'm wrong...

Now if I use it as follows:

XilExceptionHandler SendHandler;
Inst->Sendhandler = (XilExceptionHandler) stub;

where SendHandler defined above is an element of structure variable Inst
and stub is defined as

 static void stub (void)

My main doubt is when we typecast the stub function to a pointer to a function, it should pass the address of the function to the SendHandler function pointer in the structure, but can't understand how it does so?

 

[FvM]

Although it's problematic to discuss incomplete code snippets, two points are obviously wrong:
- a function pointer can be assigned to the address of a function, not the function itself
- void (pf1 *)(void) and void (pf2 *)(void * data) aren't assignment compatible