Re: Compiler bug on #elif and UNICODE

From:

"Doug Harrison [MVP]" <dsh@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Tue, 27 Mar 2007 21:32:23 -0500

Message-ID:

<2mkj03hsfl4bauntltr894bl58mksr30ed@4ax.com>

On Tue, 27 Mar 2007 18:42:19 -0700, Neo The One
<NeoTheOne@discussions.microsoft.com> wrote:

It's a very weird problem. I have the following stdafx.h:

#pragma once

#define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers
#include <stdio.h>
#include <tchar.h>

#include <windows.h>
#include <string>

using namespace std;

#ifdef UNICODE
typedef wstring tstring;
#elif defined(_UNICODE)
typedef wstring tstring;
#elif // error line
typedef string tstring;
#endif

When UNICODE and _UNICODE is defined (set thru project general settings), no
errors given. But in non-UNICODE build, I got the following error:

Error 1 fatal error C1017: invalid integer constant expression e:\my
documents\visual studio 2005\projects\win32test\stdafx.h 16

What's going on here?

You need to terminate with #else instead of #elif. Also, unless you're
going to do something different for UNICODE vs _UNICODE, you might as well
simplify it to:

#if defined(UNICODE) || defined(_UNICODE)
typedef wstring tstring;
#else // (no longer an) error line
typedef string tstring;
#endif

For that matter, I can't imagine wanting just one of UNICODE and _UNICODE
to be defined, so I might check for that condition and output an error if
it exists.

--
Doug Harrison
Visual C++ MVP