optimization - Why C++ compiler isn't optimizing unused reference variables? -

consider following program:

#include <iostream> struct test {     int& ref1;     int& ref2;     int& ref3; }; int main() {     std::cout<<sizeof(test)<<'\n'; } 

i know c++ compiler can optimize reference variables entirely won't take space in memory @ all.

i tested above demo program see output. when compile & run on g++ 4.8.1 gives me output 12. looks compiler isn't optimizing reference variables. expecting size of test struct 1. i've used -os command line option still gives me output 12. have tried program on msvs 2010 compiled /ox command line option looks microsoft compiler isn't performing optimization @ all.

the 3 reference variables unused & aren't associated other variable. why compilers aren't optimizing them?

the size of struct stays same, there nothing optimize. if create array of test should allocate right size each test. compiler cannot know used or not. that's why there no such optimization.

unused variables example new int& int inside main function. if unused, optimizer optimize away.