https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63714
--- Comment #16 from David Edelsohn <dje at gcc dot gnu.org> --- Bull Freeware provides GCC 4.8.1 for AIX 6.1. I do not know why they only provide GCC 4.6.1 for AIX 7.1. AIX 5.3 no longer is supported by IBM and newer features in GCC require object file and OS feature not provided by AIX 5.3. If a customer continues to run AIX 5.3 because they want the system to remain stable for some legacy software, I do not understand why installing the latest release of GCC would be a priority.
