Re: wcout <<a.operator wchar_t const*()[implicit] prints memory address

From:
"Alf P. Steinbach" <alfps@start.no>
Newsgroups:
microsoft.public.vc.language
Date:
Sat, 22 Mar 2008 16:50:45 +0100
Message-ID:
<13uaaishr3omi98@corp.supernews.com>
* Alf P. Steinbach:

* Angel Tsankov:

Hello! Why does the second statement in main print a memory address
(tested with VC 2003 & 2005)?

#include <iostream>

wchar_t const* f()
{
static wchar_t const Str[] = L"aaa";
return Str;
}

class Proba
{
public:
operator wchar_t const*()
{
static wchar_t const Str[] = L"aaa";
return Str;
}
};

int main()
{
std::wcout <<f(); // Prints "aaa"
std::wcout <<Proba(); // Prints some memory address
}


It's very sad that [comp.std.c++] is (or seems to be) defunct, because
this question seems to belong there.

I suggest you post it to [comp.lang.c++.moderated], because as far as I
can see -- but relying on several months old draft -- it hasn't been
fixed in C++0x.

In short, it seems you get this behavior because std::basic_ostream
provides overloads for char*, signed char* and unsigned char* arguments,
but relies on general operator<< template for wchar_t*. With the
template the argument must match exactly. It doesn't, so you get the
void const* overload.


Uhm, add some "const"s in there, also fix: "With the general template..." next
last para.

Darned keybaord.

Cheers,

- Alf

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