SIGINT was not declared in this scope - c++11

Question

Background
I am trying to build a sample REST api app for Rasbian running on Raspberry 3. I used cpprestsdk.
Sample contains the following header file:
#include <condition_variable>
#include <mutex>
#include <iostream>
static std::condition_variable _condition;
static std::mutex _mutex;
namespace cfx {
class InterruptHandler {
public:
static void hookSIGINT() {
signal(SIGINT, handleUserInterrupt);
}
static void handleUserInterrupt(int signal){
if (signal == SIGINT) {
std::cout << "SIGINT trapped ..." << '\n';
_condition.notify_one();
}
}
static void waitForUserInterrupt() {
std::unique_lock<std::mutex> lock { _mutex };
_condition.wait(lock);
std::cout << "user has signaled to interrup program..." << '\n';
lock.unlock();
}
};
}
Issue
When compiling on MacOS, no problem occurs.
When compiling in rasbian however, I get error: 'SIGINT' was not declared in this scope error.
It is clear that SIGINT definition - #define SIGINT 2 or similar - is not reachable when compiling on rasbian.
Question
Why I am getting this error on rasbian but not on macOS? Is it because compiler cannot locate signal.h?
I made sure that include_directories in CMakeLists.txt contains required include paths.
UPDATE
Error resolved when I manually added #include <csignal>.

Answer 1

You haven't included signal.h.
You're including some C++ standard library headers, and as a side effect on MacOS, these happen to include signal.h. However, that isn't specified to happen so you can't rely on it working in different implementations of those headers.
Try adding:
#include <signal.h>
at the top.

Answer 2

On Linux the header file to include is
#include <signal.h>
On MacOS the equivalent header file to include is
#include <csignal.h>
Depending on your OS, header files always change. They should both do the same thing though