C linkage for function pointer passed to C library

Question

My case is pretty simple: I want my C++ program to deal with Unix signals. To do so, glibc provides a function in signal.h called sigaction, which expects to re

Answer 1

My question is: is the extern "C" linkage specifier necessary?

For maximum portability, yes; the C++ standard only guarantees interoperability with C via functions declared extern "C".

Practically, no; most sensible ABIs (including the GNU ABI used by glibc) will use the same calling convention for C and C++ non-member (and static member) functions, so that extern "C" is only needed to share the function name between languages.

Bonus question: can uponSignal be declared static?

Yes. External linkage is only needed to access the function by name from other translation units; it's not necessary to call the function via a function pointer.