weird typedef syntax

Heya, so I can't wrap my mind a typedef'ed function pointer in a header I want to understand. It's of the form:

typedef void (*T_FUNC_CALLBACK) (UINT8 *setupPtr, UINT8 *dataPtr);

Tell me if I'm wrong: the type is void, and the name is T_FUNC_CALLBACK. But how can a function pointer be a void type? Am I missing something?

The type is "pointer to function returning void taking two arguments, each of type UINT8*".

I'm not too familiar with function ptr syntax, so I'm trying to understand: what does this typedef do for the code? Without it, I can already use *T_FUNC_CALLBACK. Since it has the same name, and same function, the typedef seems extraneous code.

Quote:

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Originally Posted by ngloosh

I'm not too familiar with function ptr syntax, so I'm trying to understand: what does this typedef do for the code? Without it, I can already use *T_FUNC_CALLBACK. Since it has the same name, and same function, the typedef seems extraneous code.

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Extraneous? You'd rather type:

Code:

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void (*) (UINT8 *setupPtr, UINT8 *dataPtr)

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Everywhere instead of:

Code:

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T_FUNC_CALLBACK

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? Weird.

EDIT: And your statement that "You can already use T_FUNC_CALLBACK" is untrue, since this typedef is what defines that name.

Quote:

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Originally Posted by ngloosh

I'm not too familiar with function ptr syntax, so I'm trying to understand: what does this typedef do for the code? Without it, I can already use *T_FUNC_CALLBACK. Since it has the same name, and same function, the typedef seems extraneous code.

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You can't use T_FUNC_CALLBACK without the typedef. What the typedef does is make the declaration

Code:

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T_FUNC_CALLBACK some_function

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equivalent to

Code:

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void (*some_function)(UINT8 *setupPtr, UINT8 *dataPtr)

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If you ever try to do *T_FUNC_CALLBACK in your code, it won't compile, in much the same way that you can't use *char to dereference a string.

cool, cool. Both of you make sense. Thanks.

A better way to do it IMO, is instead of:

Code:

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typedef void (*T_FUNC_CALLBACK) (UINT8 *setupPtr, UINT8 *dataPtr);
T_FUNC_CALLBACK ptr = &something;
ptr();

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...do...

Code:

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typedef void (T_FUNC_CALLBACK) (UINT8 *setupPtr, UINT8 *dataPtr);
T_FUNC_CALLBACK* ptr = &something;
ptr();

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It makes it more obvious it's a pointer.