value-initialization

[Andrew Koenig]

At its Dublin meeting in April, 1999, the C++ standards committee
agreed to strengthen the requirements on the initial value of
expressions of the form T(), where class T does not have a
user-defined constructor.

Because any implementation that meets the revised requirements also
meets the present requirements, and because the revision makes some
programs significantly easier to write, I would like to urge you to
make egcs follow the revised requirements as soon as possible, and to
let the C++ community know promptly once this has happened.

Here is an example of a program whose behavior is guaranteed by the
revised definition, but not by the present standard (or by egcs):


// This test is not guaranteed to detect failure, but it's pretty likely.
#include <iostream>

struct A { A() { } };

struct T {
    int a[1000000];
    A aa;
};

int main()
{
    T t = T();
    for (int i = 0; i < 1000000; ++i)
	if (t.a[i]) {
	    std::cout << "t.a[" << i << "]=" << t.a[i] << std::endl;
	    return 1;
	}
    return 0;
}


If you need any additional information, please let me know.





					Regards,

					Andrew Koenig
					ark@research.att.com

					Project Editor,
					C++ Standards Committee