Problems with macros

Problems with macros

[Alexander.Schmid]

Hi everybody,

My system configuration: Suse Linux 8.1, gcc 3.2.

I´m porting some Windows stuff to Linux. To provide Unicode support, I use the
_T(x) macro from windows <tchar.h> , which actually puts an 'L' in front of the
text 'x'. The definition sounds like this:
#define _T(x)  L ## x

This works just fine when x is a string with quotationmarks or a character, like
_T("hello world") or _T('c'), but now I encountered a problem. When I call
_T(__FILE__), gcc seems just to interpret the _T macro and not the __FILE__
macro, so it leads to an error: "L__FILE__ not known", but the result should be
the actual file name in Unicode (The _T(__FILE__) works in Visual C++, so I
think it´s a gcc problem).

Can anybody tell me why this is and how I can get around this (perhaps a special
compiler flag?), or is there no hope for this problem?

Thanks in advance,
Alex

Re: Problems with macros

[John Love-Jensen]

Hi Alex,

I'm betting that Microsoft is the one that's not quite compliant.

It works if you have a two-stage macro:

g++ -E -c test.cpp
--- test.cpp ---
#define T(x) L ## x
#define R(x) T(x)
R(__FILE__)
--- end-of-file---

Voila!  Twiddle with the macro names as appropriate, and you shouldn't need
to change any of your existing source code.

--Eljay
(I hate macros.)