using namespace std;
void g();
class A {
public :
A() { g();g();g(); cout << "Constructor of A"<< endl ;}
};
inline void g(){ cout << "vijay" <<endl; }
int main() {
A a;
}

when i use inline i get size 303488 Aug 31 12:05 a.out*

when not using inline i get size 303572 Aug 31 12:05 a.out*

You cannot predict the size of an executable. Inlining often results in LARGER code blocks, not smaller. Note the word "often". Compilers do fun things when they optimize.

Compilers are not duty-bound to optimize just because you think they should.
If you use complex, tricky code compilers will often decide not to optimize.
HPUX C compilers do this - they back down optimization levels when presented with really convoluted code.

The only way I could imagine the size decreasing is because you invoke the inline function call in just one place in your code, or that some other optimization was turned off/on because of the inline function.