Re: Anonymous-namespace references vs extern references

"Angel Tsankov" <>
Wed, 7 May 2008 09:49:22 +0300

Which of the following definitions of tcerr is preferrable and why?

// header file
namespace {
::std::wostream& tcerr = ::std::wcerr;

Don't use anonymous namespaces in header files. There's only one global
level anonymous namespace in each compilation unit. The above sneaks in
an identifier in the anonymous namespace of the each implementation file
that uses this header, and in that anon namespace there might well be
something called tcerr.

Ooops, you're right! In fact, I meant to write smth like this:

namespace tstd {
namespace {
::std::wostream& tcerr = ::std::wcerr;

Also it's a good idea to not use "T" functionality at all, and a really
bad idea to use it (more to write, more possible bugs, less portable and

So the above is wrongheaded on 2 different counts.

// header file
extern ::std::wostream& tcerr;

// source file
::std::wostream& tcerr = ::std::wcerr;

This one would be slightly less unpreferable than the first.

But do you really want your Unicode messages to be translated to some
single byte charset that you don't control (most probably Windows ANSI

I'd think not.

It's just silly.

For internal diagnostic messages and logging, go for English only, a well
known single byte charset, and deal with e.g. Unicode filenames (if you
must) explicitly, instead of relying on some unspecified lossy

In fact, I'd go for English only, but I'd like to be able to switch easily
between ANSI and UNICODE builds, possibly without changing the source code,

tstd::tstring NameOfInputFile(_T(...));
HANDLE HandleToInputFile = CreateFile(NameOfInputFile.c_str(), ...);

Cheers, & hth.,

- Alf

A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

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