Re: ETHERMTU

[Saikiran Madugula <hummerbliss () gmail com>]

Guy Harris wrote:
> On Sep 5, 2007, at 2:17 PM, Saikiran Madugula wrote:
>
> > Yes, I get warning when gencode.c gets compiled with the custom package.
> > (ofcourse standalone libpcap compiles fine).
> >
> > gcc -O2 -I.  -I<path to custom package's include files> 
> > -DHAVE_CONFIG_H  -D_U_="__attribute__((unused))" -D<XXX_ONLY> -fPIC 
> > -DPIC -c ./gencode.c
> > ./gencode.c:87:1: warning: "ETHERMTU" redefined
> > In file included from /usr/include/netinet/if_ether.h:61,
> >                 from /usr/include/netinet/ether.h:26,
> >          from 
> > /pathtocustompackage/customheader.h                          from 
> > ./pcap-int.h:55,
> >                 from ./gencode.c:65:
>
> OK, so you have a *modified* version of gencode.c; this problem doesn't 
> show up with *standard* libpcap.

Yes standard works fine ! This occurs as gencode.c includes pcap-int.h, 
which includes custom.h, which includes net/ethernet.h and the cause of 
all this. I now understand that its not fair to modify a package's files 
and blame it.

> > My apologies for loose terminology. I understand it is impossible to 
> > predict what symbols might prop up. But to my surprise something like 
> > ETHERMTU has been defined in that way and *I wish to only know the 
> > reason behind this*
>
> The reason behind this is that it's a perfectly reasonable name for the 
> MTU of an Ethernet, that MTU being 1500 bytes (1500 bytes of Ethernet 
> payload, after the 14-byte Ethernet header).
>
> > If a package supports a OS such as Linux, is it not clean way of being 
> > cautious of symbols that OS uses ?
>
> No, there is no clean way to be cautious of symbols the OS uses, except 
> not to use any symbols at all, which is a bit impractical.

I understand. Thanks for patient replies :)

Saikiran.




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