I can't believe "defined" isn't supported, but anyway, a general workaround is:
For #if defined( symbol ) || defined( symbol2 ) Add #define defined #ifndef symbol #define symbol 0 #endif #ifndef symbol2 #define symbol2 0 #endif defined will be removed and all symbols will be their original value, or 0 if they don't exist. Bill Auerbach _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Piero 74 Sent: Wednesday, January 23, 2008 12:11 PM To: Mailing list for lwIP users Subject: Re: [lwip-users] what is "defined() " ??? i know preprocessing.... i have not defined() pre-processing directive in my compiler. in general i use #ifndef SYMBOL so.. i don't know how implement this macro... suggests? 2008/1/23, Kieran Mansley <[EMAIL PROTECTED]>: On Wed, 2008-01-23 at 17:19 +0100, Piero 74 wrote: > Hi all > > in file socket .h i found this: > > #if !defined(FIONREAD) || !defined(FIONBIO) > > what is "defined" macro? have i to define in cc.h using compiler > pragma? I suggest reading an introduction to the C preprocessor - this sort of question is probably better answered by getting the necessary background knowledge, and isn't really specific to lwIP. The line in question is saying "if whoever is using this file has already defined a lot of the constants that we need, then skip this bit, otherwise define all these constants that we need". It allows the sockets.h header to both be included where these values have been pre- defined (e.g. in an OS that has its own sockets API) or in one where they have not. Kieran _______________________________________________ lwip-users mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/lwip-users
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