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.
}