Jolly good!


That'd be true.

My one concern with recommending a macro here is that 'C' macros do have serious traps for the unwary, and are therefore not to be taken in hand unadvisedly, lightly, or wantonly...

Of course, the #include approach could be "customised" with conditional compilation; eg,

shared.c
static void shared_fn( void )
{

#ifdef ISR
   // your ISR-specific code here
#endif

#ifdef MAIN
   // your main-specific code here
#endif

   // your general code here
}

isr.c
#define ISR       // enable ISR-specifics
#include shared.c // Creates a *local* function

void isr( void ) interrupt x using y
{
   // your ISR code here

   shared_fn(); // Calls *local* function

   // more ISR code here
}

main.c
#define MAIN      // enable MAIN-specifics
#include shared.c // Creates a *local* function

void main( void )
{
   // your main code here

   shared_fn(); // Calls *local* function

   // more main code here
}

As I said, I've not done this in practice, so haven't investigated the pros & cons of the two approaches - that is left as an exercise for the reader...

Of course, whichever way you go, we're dealing with the 'C' Preprocessor here; for any problems, see Andy's Handy Hint for Debugging Preprocessor Problems:
http://www.8052.com/forum/read.phtml?id=29152