selfupdate error

[jinleicrazysweet@…]

--->  Updating MacPorts base sources using rsync
receiving file list ... done

sent 36 bytes  received 69 bytes  14.00 bytes/sec
total size is 3594240  speedup is 34230.86
receiving file list ... done

sent 36 bytes  received 76 bytes  5.74 bytes/sec
total size is 512  speedup is 4.57
MacPorts base version 2.1.1 installed,
MacPorts base version 2.1.3 downloaded.
--->  Updating the ports tree
Synchronizing local ports tree from rsync://rsync.macports.org/release/tarballs/ports.tar
receiving file list ... done

sent 36 bytes  received 70 bytes  30.29 bytes/sec
total size is 54753280  speedup is 516540.38
receiving file list ... done

sent 36 bytes  received 77 bytes  45.20 bytes/sec
total size is 512  speedup is 4.53
receiving file list ... done

sent 36 bytes  received 70 bytes  30.29 bytes/sec
total size is 9346970  speedup is 88178.96
receiving file list ... done

sent 36 bytes  received 77 bytes  32.29 bytes/sec
total size is 512  speedup is 4.53
--->  MacPorts base is outdated, installing new version 2.1.3
Installing new MacPorts release in /opt/local as root:admin; permissions 0755; Tcl-Package in /Library/Tcl

checking build system type... i386-apple-darwin11.4.2
checking host system type... i386-apple-darwin11.4.2
checking target system type... i386-apple-darwin11.4.2
checking MacPorts version... 2.1.3
checking for sw_vers... /usr/bin/sw_vers
checking for defaults... /usr/bin/defaults
checking for xcode-select... /usr/bin/xcode-select
checking Mac OS X version... 10.7.5
checking Xcode location... /Applications/Xcode.app/Contents/Developer
checking Xcode version... 4.6
checking for gcc... /usr/bin/cc
checking whether the C compiler works... no
configure: error: in `/opt/local/var/macports/sources/rsync.macports.org/release/tarballs/base':
configure: error: C compiler cannot create executables
See `config.log' for more details
Command failed: cd /opt/local/var/macports/sources/rsync.macports.org/release/tarballs/base && CC=/usr/bin/cc ./configure --prefix=/opt/local --with-tclpackage=/Library/Tcl --with-install-user=root --with-install-group=admin --with-directory-mode=0755 --enable-readline && make && make install SELFUPDATING=1
Exit code: 77
Error: /opt/local/bin/port: port selfupdate failed: Error installing new MacPorts base: command execution failed

I installed Xcode,so I want know the reason for the error

[larryv (Lawrence Velázquez)]

Replying to jinleicrazysweet@…:

checking whether the C compiler works... no
configure: error: in `/opt/local/var/macports/sources/rsync.macports.org/release/tarballs/base':
configure: error: C compiler cannot create executables

Did you install the Command Line Tools? If you have Xcode 4, do this by going to Xcode > Preferences > Downloads > Components.

[jmroot (Joshua Root)]

We of course require a working C compiler. Trac is not a support venue, so please post to the macports-users list if you need help.