Using / accessing function pointer declaration externally

[Vaclav_]

OK, this is really simple question, with example code to boot. The function pointer declaration is this void (*gpf_isr)(void) = (0UL); It is used by this function void UOTGHS_Handler( void ) { if (gpf_isr) gpf_isr(); } and I access it like so extern void (*gpf_isr)(void); then I assign my local poiter / version of the function gpf_isr = ( object ) . UTOGHS_Handler; The silly question why this also get pass the compiler , no errors extern void (*gpf_isr)(void) = (0UL); The pointer gets reassigned , but ...

[CPallini]

See, for instance How to define extern variable along with declaration?[^]

[Lost User]

The key point here is the extern qualifier. That states that the variable can be referred to from any module in the final linked executable, but only one instance of it will actually exist.

[Vaclav_]

That is pretty clear that defining the variable is OK, but if optioned GCC will give a warning. Kind like deleting a file and being ask "are you sure?" Thanks .

[CPallini]

Yes. You may find (on the web) folks arguing that warning is not legitimate. In a clean implementation you don't qualify with extern the variable in the source file wherein you define it.