How to declare function pointer in header and c-file?

A function pointer is still a pointer, meaning it's still a variable.

A function pointer is still a pointer, meaning it's still a variable. If you want a variable to be visible from several source files, the simplest solution is to declare it extern in a header, with the definition elsewhere. In a header: extern void (*current_menu)(int); In one source file: void (*current_menu)(int) = &the_func_i_want.

Ty, now it works – user1106072 Dec 19 '11 at 14:53 the ampersand isn't strictly necessary – Dave Dec 19 '11 at 16:27 That is true, @Dave. In C, it's a stylistic choice of mine for clarity. In C++ it's sometimes required in certain template contexts, so I just do it for consistency.

– Drew Dormann Dec 19 '11 at 17:06.

It's often helpful to use typedef with function pointers, so you can name the type to something descriptive: typedef void (*MenuFunction)(int); Then you would have a global variable of this type, probably in menus. C, and declared (with extern) in menus. H: static void my_first_menu_function(int x) { printf("the menu function got %d\n", x); } MenuFunction current_menu = my_first_menu_function; From main.

C, you can then do: #include "menu. H" current_menu(4711); to call whatever function is currently pointed at by current_menu.

Very true! Function is also available if you have access to boost or C++11. – Drew Dormann Dec 19 '11 at 15:12.

A pointer function itself does not have a function definition. It's nothing more than a pointer to a type, the type being specified by the return type of the function and the parameter list. What you need to do is define a function with the same parameter list and return type, then use your pointer function to hold that function's address.

You can then call the function through the pointer.

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