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RE: [lwip-devel] opt.h - LWIP_EVENT_API

From: Bill Auerbach
Subject: RE: [lwip-devel] opt.h - LWIP_EVENT_API
Date: Mon, 6 Dec 2010 10:28:17 -0500

If we did change opts.h, this is backward compatible:

** Current implementation **
#define LWIP_EVENT_API                  0
#define LWIP_CALLBACK_API               1
#define LWIP_EVENT_API                  1
#define LWIP_CALLBACK_API               0

** Compatible change **
#define LWIP_EVENT_API                  0
#define LWIP_CALLBACK_API               (! LWIP_EVENT_API)

Now doing #define LWIP_EVENT_API 0 is OK and works as expected.  This is also 
better because it guarantees the options are opposite.

If someone does:

#define LWIP_CALLBACK_API               1

without defining LWIP_EVENT_API it will potentially redefine LWIP_CALLBACK_API 
generating a compiler warning or error.  This is the case with the current code 
as well.  To be thorough we can #undef LWIP_CALLBACK_API before the #define of 

I can provide this patch or a patch to do a compile time check, yes.  I would 
like to ask why do you prefer to not fix opts.h and compile-time check it 


>-----Original Message-----
>From: address@hidden
>[mailto:address@hidden On
>Behalf Of Kieran Mansley
>Sent: Monday, December 06, 2010 10:00 AM
>To: lwip-devel
>Subject: Re: [lwip-devel] opt.h - LWIP_EVENT_API
>On Mon, 2010-12-06 at 09:45 -0500, Bill Auerbach wrote:
>> * LWIP_EVENT_API and LWIP_CALLBACK_API: Only one of these should be
>> set to 1.
>> Which implies not explicitly setting it to 0, but I don’t think I see
>> any options that don’t allow a 0 for off and a 1 for on.  This one is
>> “No define for off” and “Define 1 for on”.  Seems inconsistent to me.
>It does look wrong.  I'd favour not trying to fix it up in opt.h and
>instead asserting in our compile time checks that:
>1) One of them is set (I think this is required?  Am I wrong?)
>2) Both of them aren't set
>opt.h could then I suppose have a section to fix it up where neither
>have been set so that we get a sensible default.
>Could you raise a bug on savannah, and if you're feeling enthusiastic
>suggest a patch?
>lwip-devel mailing list

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