[boost] Re: Re: Re: Re: New patch for operators.hpp uploaded

From: Marc Duflot (m.duflot_at_[hidden])
Date: 2002-10-24 07:47:04

Daniel Frey wrote:

> #include <iostream>
> using namespace std;
> 
> struct X
> {
>    X() { cout << "X"; }
>    X( const X& ) { cout << "C"; }
> };
> 
> X f()
> {
>    return X();
> }
> 
> X g()
> {
>    X x;
>    return x;
> }
> 
> #define TEST( code ) \
>    cout << #code << "\t: "; code; cout << endl
> 
> int main()
> {
>    TEST( f() );
>    TEST( g() );
>    TEST( X( f() ) );
>    TEST( X( g() ) );
>    TEST( X x1( f() ); );
>    TEST( X x2( g() ); );
>    TEST( X x3 = f(); );
>    TEST( X x4 = g(); );
> }

g++ 2.95.2
f()     : X
g()     : XC
X( f() )        :
X( g() )        :
X x1( f() );    : X
X x2( g() );    : XC
X x3 = f();     : X
X x4 = g();     : XC

g++ 3.0.4
f()     : X
g()     : XC
X( f() )        :
X( g() )        :
X x1( f() );    : XC
X x2( g() );    : XCC
X x3 = f();     : X
X x4 = g();     : XC

g++ 3.1 and 3.2
f()     : X
g()     : X
X( f() )        :
X( g() )        :
X x1( f() );    : X
X x2( g() );    : X
X x3 = f();     : X
X x4 = g();     : X

Intel C++ 6.0
f()     : X
g()     : X
X( f() )        :
X( g() )        :
X x1( f() );    : XC
X x2( g() );    : XC
X x3 = f();     : X
X x4 = g();     : X

SGI MipsPro Compiler 
f()     : X
g()     : X
X( f() )        :
X( g() )        :
X x1( f() );    : XC
X x2( g() );    : XC
X x3 = f();     : X
X x4 = g();     : X

Visual C++ 6
f()     : X
g()     : XC
X( f() )        :
X( g() )        :
X x1( f() );    : X
X x2( g() );    : XC
X x3 = f();     : X
X x4 = g();     : XC

Summary:
* g++ 3.0.4: bad
* g++ 2.95.2 and Visual C++ 6: average: RVO but not NRVO
* Intel C++ 6.0 and SGI MipsPro Compiler (both based on EDG): good: RVO and
     NRVO except with X x( f() );
* g++ 3.2: best

Every compiler outputs nothing for X( f() ) and X( g() ).

-- 
Marc Duflot
http://vesta.ltas.ulg.ac.be/~duflot/