Ubuntu14.04下ns-2.35的OLSR问题求助：补丁安装后ntohl重定义警告

Hey there, let's sort out this ntohl redefinition warning you're facing after installing the umolsr patch. Here's the breakdown of the issue and how to fix it:

Why the Warning Occurs #

The umolsr-ns235_v1.0-2014.patch adds an incorrect custom definition of the ntohl macro in the file dymoum/ns/dymo_um.h:

#define ntohl(x) x ^

But your system's standard library already defines ntohl correctly in /usr/include/netinet/in.h as a proper byte-swapping function (__bswap_32(x)). This duplicate definition triggers the compiler warning.

Step-by-Step Solution #

1. Open the conflicting header file with your preferred editor (we'll use vim here):

   vim /home/uday/ns-allinone-2.35/ns-2.35/dymoum/ns/dymo_um.h
   

2. Remove or comment out the faulty macro:
   Locate the line #define ntohl(x) x ^ and either delete it entirely, or comment it out like this:

   // #define ntohl(x) x ^
   

   Note: The original x ^ definition is likely a bug—it doesn't perform valid network-to-host byte order conversion. Removing it is the safest choice, as your system's standard ntohl implementation will handle this correctly.
   If you want a more cautious approach (in case the patch expects this macro in some edge case), wrap it in a conditional check to avoid redefining an existing macro:

   #ifndef ntohl
   #define ntohl(x) x ^
   #endif
   

3. Recompile ns-2.35 to apply the fix:
   Navigate back to your ns-2.35 directory and run these commands:

   cd /home/uday/ns-allinone-2.35/ns-2.35
   make clean
   make
   make install
   

This should resolve the redefinition warning and let your patched ns-2.35 build without issues.

内容的提问来源于stack exchange，提问作者Uday Kumar Manchikatla