Re: sizeof()

From:
"James Kanze" <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Wed, 7 Mar 2007 09:35:58 CST
Message-ID:
<1173266098.310511.198930@j27g2000cwj.googlegroups.com>
On Mar 7, 9:01 am, "maverick" <mod...@gmail.com> wrote:

The following program's output is 4 bytes on g++(v3.2.2) RH Linux (32
bit).

on printing, individually, the sizeof(g()) and sizeof(h()) it o/ps 4
and 1 respectively.

I am wondering what the standard says about sizeof ( expr?expr:expr)


It says that it will be the size of the resulting type. Like
every expression in C++, a ?: expression has a statically
evaluated type.

#include<iostream>
using namespace std;

bool f()
{
    return false;
}

int g()
{
    return 1;
}

char h()
{
    return 's';
}

int main(int a, char* b[])
{
    if ( a == 1 )
    cerr << sizeof(f()?h():g()) <<endl;
    else
    cerr << sizeof(f()?g():h()) << endl;
}


Both line should output the same thing as sizeof(int), since
that is the type of the ?: expression in both cases.

Note that you can also check this by using function overloading:

    void
    showType( int )
    {
        std::cout << "int" << std::endl ;
    }

    void
    showType( char )
    {
        std::cout << "int" << std::endl ;
    }

    showType( condition ? g() : h() ) ;

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