As far as I can tell, the "#if defined()" has been part of the C standard since the 1980's; it appears to have been added at the same time as "#elif" and "#error"... If your compiler really does not support this identifier, then I suspect you will have much bigger problems trying to compile this code - or any other code written in the last 20 years!
Jared From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Piero 74 Sent: Wednesday, January 23, 2008 09:11 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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