I just downloaded Ruby 1.6.6, and did "configure" and "make" on my AIX 
4.3.3 machine. The make crapped out with the following messages:

compiling digest/rmd160
        cc -g  -DHAVE_CONFIG_H -I/home/tgphelps/ruby-
1.6.6/ext/digest/rmd160/..
-I/home/tgphelps/ruby-1.6.6 -I/home/tgphelps/ruby-1.6.6 -
I/usr/local/include -DH
AVE_SYS_CDEFS_H -DHAVE_INTTYPES_H -DHAVE_UNISTD_H  -c rmd160.c
"rmd160.h", line 38.1: 1506-485 (S) Parameter declaration list is 
incompatible w
ith declarator for __BEGIN_DECLS.
"rmd160.h", line 49.1: 1506-276 (S) Syntax error: possible missing '{'?
"rmd160.c", line 131.21: 1506-045 (S) Undeclared identifier context.
"rmd160.c", line 151.9: 1506-226 (S) The ":" operator is not allowed 
between "vo
id" and "int".
"rmd160.c", line 152.9: 1506-226 (S) The ":" operator is not allowed 
between "vo
id" and "int".
"rmd160.c", line 361.9: 1506-226 (S) The ":" operator is not allowed 
between "vo
id" and "int".
"rmd160.c", line 362.9: 1506-226 (S) The ":" operator is not allowed 
between "vo
id" and "int".
"rmd160.c", line 420.9: 1506-226 (S) The ":" operator is not allowed 
between "vo
id" and "int".
"rmd160.c", line 421.9: 1506-226 (S) The ":" operator is not allowed 
between "vo
id" and "int".
make: 1254-004 The error code from the last command is 1. 


If someone wants any more information about this, I'll supply whatever is 
needed. And if you know the fix for this, please let me know. In the 
meantime, I'll see what I can find out on my own.