16.2.4 Using Macros to Declare Simple ISRs
If an interrupt handler does not require any of the optional parameters of the interrupt attribute, then a simplified syntax may be used. The following macros are defined in the device-specific header files:
#define _ISR __attribute__((interrupt))
#define _ISRFAST __attribute__((interrupt, shadow))
For example, to declare an interrupt handler for external interrupt 0:
#include <xc.h>
void _ISR _INT0Interrupt(void);
To declare an interrupt handler for the SPI1 interrupt with fast context save:
#include <xc.h>
void _ISRFAST _SPI1Interrupt(void);