A few months back I was asked to look at packaging R for AIX. The first roadblock was that I also needed fortran to build R.
Since I did not have access to IBM Fortran I needed to improve my gcc compiler to include gfortran.
Yesterday, the requester and I finally got around to testing what I had packaged - and the memory space was too small. Could it be packaged as 64-bit?
Well, with the IBM compilers - one easy way is to just say that OBJECT_MODE=64. Unfortunately, gcc and gfortran do not understand that (while ld does very well, and it refuses to use the 32-bit objects being produced).
I shall save you all my trials.
The simple solution was to just set OBJECT_MODE=64 (be sure and export that) and then set (and export both) CFLAGS to "-maix64 -O2" and FFLAGS="-maix64 -O2"
Happy me!