jay.lee jay.lee - 1 year ago 105
C Question

Call a void* as a function without declaring a function pointer

I've searched but couldn't find any results (my terminology may be off) so forgive me if this has been asked before.

I was wondering if there is an easy way to call a

as a function in C without first declaring a function pointer and then assigning the function pointer the address;

ie. assuming the function to be called is type

void *ptr;
ptr = <some address>;
((void*())ptr)(); /* call ptr as function here */

with the above code, I get error C2066: cast to function type is illegal in VC2008

If this is possible, how would the syntax differ for functions with return types and multiple parameters?

Answer Source

Your cast should be:

((void (*)(void)) ptr)();

In general, this can be made simpler by creating a typedef for the function pointer type:

typedef void (*func_type)(void);
((func_type) ptr)();

I should, however, point out that casting an ordinary pointer (pointer to object) to or from a function pointer is not strictly legal (although it is a common extension).

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