error while making indent 2.2.9

Hi. I have an error while building indent-2.2.9, but actually i have such error on 
older indents too.

indent.h:100: error: previous declaration of  output' was here
output.c: In function  open_output':
output.c:1149: warning: incompatible implicit declaration of built-in function  exit'

I think the problem in first case is that there are multiplying declaration of output 
file, cause i look in other sources and also find there extern decalration of FILE 
*output. So we have there including of two headers which both has declaration of extern 
FILE *output. I solve this problem by commenting line 100 in src/indent.h. Dunno how 
would it works but it helps.

On second error we have void open_output which returns (or I'm wrong?) some values on 
exit. I've also commented line 149 in src/output.c. Only after that i was able to make 
indent.

I have gcc-4.2.0 on kubuntu 7.04 feisty.
I'm sorry, but I'm not a super pro in c/c++ and I'm a beginner in linux, so pls answer 
me where was problem : in my brain or in program.. or maybe i have such errors cause 
use the last gcc?

p.s.: also English isn't my native, so I'm also sorry for all grammar mistakes.