AVR-Chat

I have code running on my ATMega128. The software is TWI/I2C (talking
to a DS1307).   When I compile it for my ATMega16, it gets stuck in
the following file:

TWI.C

At the following location: 

WAIT_FOR_TWINT \
  for ( \
       toCounter = toValue; \
       ( toCounter != 0 ) && ( ( TWCR & _BV( TWINT ) ) == 0 ); \
  )


I am using GCC.

Why does it not get stuck here when running on the Mega128 but does
get stuck when running on my Mega16?

I know it gets stuck here because I am using the UART to trace code
[with Windows Terminal].

I have been playing with GCC for a year now.  Is CodeVision (or some
other compiler) easier to work with?

Thanks.