Question

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is i=i++ truly a undefined behavior?

i just want too explain ++ and — to my students and show them some code about them in visual studio 2010
I just test this code on it

int main(){
   int a=3;
   int b=3;
   a=a++;
   cout<<a<<endl;
   cout<<b++<<endl;
}

I expect that both of cout print 3 but the first cout print 4!!!!
I test it in g++ and both of couts print 3…
what’s wrong???

Answer 1

The behavior of a=a++ is undefined. If you’d like to increment a, use a++ instead.