Re: [avr-gcc-list] odd left-shift behavior, avr-gcc 4.1.2

[Dean Ferreyra]

John Regehr wrote:
>> operand."  I believe this means that the result of the shift in your
>> example is a uint16_t, so you get 0xfffe which is then promoted to an
>> int32_t on assignment to x.
> 
> Ok but notice that the same code gives a different result on x86-gcc.  I 
> think this means that the only choices are: implementation defined 
> behavior, undefined behavior, or compiler bug.

The native int size on your x86 compiler is probably 32 bits.  Each
argument to the shift is promoted to int first; that's the bit about
"integer promotions" and this gets you answer you're expecting.  I
believe the native int size on avr-gcc is 16 bits, so your left operand:

  ((uint16_t)0xffffL)

stays at 16 bits on the AVR.

Dean