Re: [Xenomai] panic macro interference with xerces api.

[g.strobbe@telenet.be]

----- Original Message -----
> From: "Gilles Chanteperdrix" <gilles.chanteperdrix@xenomai.org>
> To: "Stéphane ANCELOT" <sancelot@free.fr>
> Cc: xenomai@xenomai.org
> Sent: Tuesday, November 10, 2015 3:28:14 PM
> Subject: Re: [Xenomai] panic macro interference with xerces api.
> 
> On Tue, Nov 10, 2015 at 02:26:54PM +0100, Stéphane ANCELOT wrote:
> > Hi,
> > 
> > I don't know if there might be a  big impact, but I noticed, depending
> > on the order we include headers , that
> > there was a panic macro interfering with xercesc api headers.
> > 
> > #include <alchemy/task.h>
> > #include <xercesc/dom/DOMException.hpp>
> > 
> > 
> > /usr/xenomai-3.0-igb/include/boilerplate/ancillaries.h:64:10: error:
> > expected identifier before '__func__'
> >    __panic(__func__, __fmt, ##__args)
> 
> Well, if the two headers define the same macro, there are not many
> solutions: arrange for not having to include them in the same file.
> It should not be too hard, since a real-time thread using
> alchemy/task.h has no business using an xml library, probably only
> using linux services which a real-time task can not use without
> switching to secondary mode.
> 
> --
> 					    Gilles.
> https://click-hack.org
> 
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> 

I recently had a similar issue with the macro

#define panic(__fmt, __args...)			\
	__panic(__func__, __fmt, ##__args)

defined in ancillaries.h

The preprocessor modified virtual void panic(const PanicHandler::PanicReasons reason) = 0;

in the included xercesc/util/PanicHandler.hpp

resulting in a compilation error.

>From the gcc preprocessor manual https://gcc.gnu.org/onlinedocs/cpp/Undefining-and-Redefining-Macros.html#Undefining-and-Redefining-Macros

If a macro ceases to be useful, it may be undefined with the ‘#undef’ directive. ‘#undef’ takes a single argument, the name of the macro to undefine. You use the bare macro name, even if the macro is function-like. It is an error if anything appears on the line after the macro name. ‘#undef’ has no effect if the name is not a macro.  

So after the #include <alchemy/task.h> I placed
            
#undef panic

No problems since. Should also be fine as a solution, no?

Best regards,

Gino