After upgrading Mac OS X to newest version Mavericks, I attempted to selfupdate my Macports, but it failed:
$ sudo port -v selfupdate
---> Updating MacPo
I had this issue on Mountain Lion and it was actually to do with MacPorts looking at an old XCode path (I had several versions including betas installed). I ran with the -d option and checked the config.log file at /opt/local/var/macports/sources/rsync.macports.org/release/base and it reported some errors:-
--- snip ---
...
configure:3331: checking for C compiler version
configure:3340: gcc --version >&5
Configured with: --prefix=/Applications/Xcode5-DP3.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
xcrun: Error: could not stat active Xcode path '/Applications/Xcode5-DP3.app/Contents/Developer'. (No such file or directory)
configure:3351: $? = 0
configure:3340: gcc -v >&5
Configured with: --prefix=/Applications/Xcode5-DP3.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
xcrun: Error: could not stat active Xcode path '/Applications/Xcode5-DP3.app/Contents/Developer'. (No such file or directory)
...
--- snip ---
So I gave it the correct path using:-
sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer
and that fixed it.
I got my clues from this useful page.