Bit operator: Left shift and Right shift (Signed or unsigned? )

Posted 2020-09-11 liguangsunls

No matter left shift or right shift, the result‘s sign should always be the same as its left operand.

By default, const numbers in C/C++ is signed.

-Wsign-compare

{

     unsigned int j = 3;

     int k = 5;

     

     if (j == (1 << (j)));  //warning: comparison between signed and unsigned integer expressions.

     if (j == (((unsigned int)1) << (j)));

     if (k == (1 << (k)));

     if (k == (((unsigned int)1) << (k))); //warning: comparison between signed and unsigned integer expressions.

     if (j == (j >> 1));

     if (j == (k >> 1)); //warning: comparison between signed and unsigned integer expressions.

     if (k == (k >> 1));

     if (k == (j >> 1)); //warning: comparison between signed and unsigned integer expressions.

}