Why isn't my SysTick_Handler() being called in my LPCxpresso C++ Project?
From https://rowley.zendesk.com/entries/20986562-LPC1114-IRQ-Handlers-in-C-work-in-C-do-not-work


  You need to declare your interrupt handler as a C function otherwise
  the function will not override the default handler.
  
  So for example you could do something like the following to make the
  declaration work in both C or C++:


#ifdef __cplusplus
extern "C" {
#endif

void irq_handler();

#ifdef __cplusplus
}
#endif


I assume changing irq_handler() in the code above to your SysTick_Handler code will then work. e.g.

extern "C" {
    void SysTick_Handler(void)
    {
        timerCounter++;  // these variables are all declared globally in main.cpp
        timer_10ms_tick = true;
        if ((timerCounter % 10) == 0)  //every 100ms
        {
            timer_100ms_tick = true;
        }
        if ((timerCounter % 100) == 0)  //every 1000ms
        {
            timer_1000ms_tick = true;
        }
    }
}