c++ - Why doesn't left bit-shift, "<<", for 32-bit integers work as expected when used more than 32 times? -

when write following program , use gnu c++ compiler, output 1 think due rotation operation performed compiler.

#include <iostream>  int main() {     int = 1;     std::cout << (a << 32) << std::endl;      return 0; } 

but logically, it's said bits lost if overflow bit width, output should 0. happening?

the code on ideone, http://ideone.com/vptwj.

this caused due combination of undefined behaviour in c , fact code generated ia-32 processors has 5 bit mask applied on shift count. means on ia-32 processors, range of shift count 0-31 only. ¹

from the c programming language ²

the result undefined if right operand negative, or greater or equal number of bits in left expression’s type.

from ia-32 intel architecture software developer’s manual ³

the 8086 not mask shift count. however, other ia-32 processors (starting intel 286 processor) mask shift count 5 bits, resulting in maximum count of 31. masking done in operating modes (including virtual-8086 mode) reduce maximum execution time of instructions.

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¹ http://codeyarns.com/2004/12/20/c-shift-operator-mayhem/

² a7.8 shift operators, appendix a. reference manual, c programming language

³ sal/sar/shl/shr – shift, chapter 4. instruction set reference, ia-32 intel architecture software developer’s manual