[Bug c++/64940] New: Question: is it possible to build a single gcc/g++ that will work on mult. OS versions?

[bill.torpey at ullink dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64940

            Bug ID: 64940
           Summary: Question:  is it possible to build a single gcc/g++
                    that will work on mult. OS versions?
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bill.torpey at ullink dot com

We're trying to build a single gcc/g++ toolchain that can run from a
network-mounted filesystem, and be usable from multiple OS versions.

In our specific case, we need to support RH/CentOS 5 & 6.

Our approach has been to build on RH5 with the idea that glibc is
backward-compatible.  That mostly works, but with one major problem.

When building on RH5, the gcc build creates a features.h in include-fixed that
is specific to RH5.  (Specifically, __USE_XOPEN2K8 is not defined, which causes
compile errors when building on RH6).

Is there a way to build gcc/g++ in a generic fashion such that include-fixed
does not contain a features.h, but instead picks up the (OS-specific) version
from /usr/include?

FWIW, we've google'd ourselves silly trying to answer this question, and the
only solution appears to be to build a "cross" compiler, but it's not clear how
to do that.

In particular, the approach we've tried (specifying
--target=x86_64-unknown-linux-gnu to configure) doesn't seem to prevent the
creation of a system-specific features.h.

Any suggestions would be much appreciated!