I have built GPC 20041218 on GCC 3.3.4 on AIX 5.2, and thought it 
might be useful to document my experiences. I wanted to have the 
capacity to build 64 bit programs, however only 32 bit libraries are 
installed for GPC. Following my earlier post http://www.gnu-
pascal.de/crystal/gpc/en/mail11115.html Waldek suggested trying build 
a 64 bit version of GCC including GPC. However having tried various 
strategies I was not successful in building a 64 bit only version of any 
version of GCC, even without GPC. So I tried to just build a 64 bit 
libgpc.a. I eventually achieved this  
 
export OBJECT_MODE = 64
export CFLAGS=-maix64
then run ./configure in ...gcc3.3.4/gcc/p/rts directory 
edit Makefile
add -maix64 to CFLAGS (CFLAGS=-O2)
  
copy libgpc.a to    ...lib/gcc-lib/power..../3.3.4/ppc64 
This allowed me generate 64 bit programs. My program contained a 
reference to the memavail function in  system.pas. I had earlier had 
some problems with this function in 32 bit mode when it gave an error 
http://www.gnu-pascal.de/crystal/gpc/en/mail11086.htm
In 64 bit mode the use of this function did not report an error but partly 
disabled the operating system, which should have been quite 
impossible for a normal user without root privileges! The operator had 
to reset the machine following this error. Programs without this function 
call seem to work fine.