On 4/13/07, Marcus Meissner <[EMAIL PROTECTED]> wrote:
On Fri, Apr 13, 2007 at 05:38:03AM -0400, Ken Takusagawa wrote: > What's going on here? I'm expecting the answer 0, but get 2. > > #include <stdio.h> > int main(){ > unsigned x=1; > printf("%u\n",(x<<33)); > /* outputs "2" on gcc 4.1.2 on x86_32 */ > > /* > [#4] The result of E1 << E2 is E1 left-shifted E2 bit > positions; vacated bits are filled with zeros. If E1 has an > unsigned type, the value of the result is E1*2^E2, reduced > modulo one more than the maximum value representable in the > result type. > > http://std.dkuug.dk/JTC1/SC22/WG14/www/docs/n843.htm > */Read from just 1 paragraph above the last sentence: [#3] The integer promotions are performed on each of the operands. The type of the result is that of the promoted left operand. If the value of the right operand is negative | or is greater than or equal to the width of the promoted left operand, the behavior is undefined. Ciao, Marcus
I see, so in this case, the undefined behavior happens to return "2".
