Bit OPERATOR: Left shift and right shift (signed or unsigned? )

No matter left shift or right shift, the result's sign shoshould 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 .}