Implementing SysTick_Handler via exteranl function

I am implementing SysTick and running into few problems. Attached is part of the core code which should let me hook SysTick_Handler to locally defined sysTickHook. I really lack a simple way to verify that SysTick_Handler is actually invoked, but working on that.

I tried to verify that my local definition of sysTickHook gets compiled by changing the return to bool. I expected compiler to complain about it , but it did not.

So the question is - is that normal for compiler not to verify externally implemented function or am I doing this "hooking " all wrong?

Appreciate your input. Jim

extern void svcHook(void);
extern void pendSVHook(void);
extern int sysTickHook(void);

/* Cortex-M3 core handlers */
void NMI_Handler       (void) __attribute__ ((weak, alias("__halt")));
void HardFault_Handler (void) __attribute__ ((weak, alias("__halt")));
void MemManage_Handler (void) __attribute__ ((weak, alias("__halt")));
void BusFault_Handler  (void) __attribute__ ((weak, alias("__halt")));
void UsageFault_Handler(void) __attribute__ ((weak, alias("__halt")));
void DebugMon_Handler  (void) __attribute__ ((weak, alias("__halt")));
void SVC_Handler       (void) { svcHook(); }
void PendSV_Handler    (void) {  pendSVHook(); }

void SysTick_Handler(void)
  if (sysTickHook())


  // Increment tick count each ms