"warning: (759) expression generates no code" WHY?

I'm running MPLABX v5.45, and XC8 v2.31 compiler with the PRO dongle. The processor is 16F18254. The two variables divisor and dividend are both __int24's.  time_to_go is an unsigned int.
The lines are part of a function, and I get the above (759) warning at line 101. It says:
sums.c:101:: warning: (759) expression generates no code
sums.c:103:: warning: (760) portion of expression has no effect
...
100  if (divisor == 0) //catch division by zero:
101      time_to_go = 1990;
102  else
103      time_to_go = (unsigned int)(dividend/divisor);
 
Now I really want to be sure to catch division by zero, and can't see what's wrong with line 103 either. Can anyone steer me onto the right path, please?

You guess right! Doh.
 
I've got the same code in two places with different target registers. sad:  That'll teach me to use legacy code (of mine) without noticing that.
 
It's a good thing someone's awake! Thanks for spotting that. 

He, he. Just popped in to complain about this.. Ie:
 

void foo(void)
{
int bar = 0;
.. more code
}

 
I assume that it flags this as "generates no code" because local variables are automatically zeroed on creation?
 
 

if (ax==3);
 
Another example of source code not generating any object code.
 

nigelwright7558
if (ax==3);
 
Another example of source code not generating any object code.
 

Impossible to comment without seeing the surrounding code.
 

I assume you don't use (read) bar in the snipped code. Local variables are NOT initialized automatically.

My mistake, the variable(s) it complained about were actually global ones.

Good point. I missed the semi-colon, so didn't understand what he was getting at.
 

nigelwright7558

andersm
 
It's an empty true-statement, so a NOP.
 

if (ax == 3) {
}

Compiler says "generates no code"

An empty statement is not a NOP but just "nothing".
Now, why should the compiler genrate code for the comparison if just nothing is to be done in the true-branch.
Keep in mind that this compiler is optimizing!