Bitwise left shifting of integer by more than 31 times

Question

main()
{
   int i=-1,j=32,k;
   k=i<<j;
   printf("i=%d j=%d k=%d\n",i,j,k);
}

output:

i=-1 j=32,k=-1

If I am taking j=33 then k=-2 and if j=34 then k=-4.its repeating after 32 times left shift i.e if j=64,k becomes -1 and if j=65 then k=-2.but logically bit should be lost i.e output is 0.what is happening here.

Sorry for asking such a question. I am beginner so I'm unable to understand what the compiler does here. Can you explain?

The typical behaviour (although not standardized) that I see is that it results in a shift modulo 32. — Claudia, Mar 12 '14 at 02:12

score 1 · Answer 1 · answered Oct 10 '13 at 13:46

You cannot count on getting a meaningful result when shifting a value by an amount equal to or greater than its size. From the standard:

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.

Bitwise left shifting of integer by more than 31 times

1 Answers1