Universal archs on macports on OSX systems upgraded from OSX 10.5

[JamesC1]

On OSX 10.6.8, I was failing to follow these instructions: ​https://trac.macports.org/wiki/LibcxxOnOlderSystems including the older version here: ​https://web.archive.org/web/20170331190323/https://trac.macports.org/wiki/LibcxxOnOlderSystems

The output was one cycle, among many, was:

sh-3.2# port install clang_select
--->  Scanning binaries for linking errors
--->  No broken files found.                             
--->  Found 5 broken ports, determining rebuild order
You can always run 'port rev-upgrade' again to fix errors.
The following ports will be rebuilt:
 ncurses @6.1
 gettext @0.19.8.1
 llvm-3.4 @3.4.2
 cctools @895+llvm34
 ld64-127 @127.2+llvm34
Continue? [Y/n]: Y
Warning: All compilers are either blacklisted or unavailable; defaulting to first fallback option
--->  Computing dependencies for libcxx
--->  Fetching archive for libcxx
--->  Attempting to fetch libcxx-5.0.1_4+universal.darwin_10.i386-ppc.tbz2 from http://kmq.jp.packages.macports.org/libcxx
--->  Attempting to fetch libcxx-5.0.1_4+universal.darwin_10.i386-ppc.tbz2 from https://packages.macports.org/libcxx
--->  Attempting to fetch libcxx-5.0.1_4+universal.darwin_10.i386-ppc.tbz2 from https://ywg.ca.packages.macports.org/mirror/macports/packages/libcxx
--->  Building libcxx
Error: Failed to build libcxx: command execution failed
Error: See /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_libcxx/libcxx/main.log for details.
Error: Problem while installing libcxx
Error: rev-upgrade failed: Error rebuilding ncurses
Error: Follow https://guide.macports.org/#project.tickets to report a bug.
sh-3.2#

I ended up fixing the problem by changing my universal architectures in /opt/local/etc/macports/macports.conf as follows:

# CPU architectures to use for Universal Binaries (+universal variant)
#universal_archs                i386 ppc  # breaks libcxx binary support
universal_archs         i386 x86_64

which enabled me to find the prebuilt libcxx here: ​https://packages.macports.org/libcxx

Anyone whose macports started out on OSX 10.5 could have this problem. Should it be documented on, or linked from the libcxx page above?