the gringo's building error while it is installing opam

[心如烛光]

Hi,everybody!
    Thank's for Daniel's help.I have manually installed re2c for opam successfully.However,another error comes with the gringo's installation.Just as before,I have tried to clean and reinstall the port.But it doesn't work.What's the problem?
The terminal and the log:
Terminal:
$ sudo port install opam
--->  Computing dependencies for opam
--->  Dependencies to be installed: aspcud gringo
--->  Building gringo
Error: org.macports.build for port gringo returned: command execution failed
Error: Failed to install gringo
Please see the log file for port gringo for details:
    /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_math_gringo/gringo/main.log
Error: The following dependencies were not installed: aspcud gringo
To report a bug, follow the instructions in the guide:
    http://guide.macports.org/#project.tickets
Error: Processing of port opam failed





The log:
version:1
:debug:main changing euid/egid - current euid: 0 - current egid: 0
:debug:main egid changed to: 501
:debug:main euid changed to: 502
:debug:main Executing org.macports.main (gringo)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.archivefetch (gringo)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.fetch (gringo)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.checksum (gringo)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.extract (gringo)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.patch (gringo)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.configure (gringo)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:build build phase started at Sat Sep 19 08:43:20 CST 2015
:notice:build --->  Building gringo
:debug:build Executing org.macports.build (gringo)
:debug:build port disallows a parallel build
:debug:build Environment: 
CC_PRINT_OPTIONS='YES'
CC_PRINT_OPTIONS_FILE='/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_math_gringo/gringo/work/.CC_PRINT_OPTIONS'
CPATH='/opt/local/include'
LIBRARY_PATH='/opt/local/lib'
MACOSX_DEPLOYMENT_TARGET='10.8'
:debug:build Assembled command: 'cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_math_gringo/gringo/work/gringo-4.4.0-source" && scons --build-dir=release gringo clingo'
:debug:build Executing command line:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_math_gringo/gringo/work/gringo-4.4.0-source" && scons --build-dir=release gringo clingo 
:info:build scons: Reading SConscript files ...
:info:build Checking for bison 2.5... (cached) yes
:info:build Checking for re2c... (cached) yes
:info:build Checking whether the C++ compiler works... no
:info:build error: no usable C++ compiler found
:info:build Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_math_gringo/gringo/work/gringo-4.4.0-source" && scons --build-dir=release gringo clingo 
:info:build Exit code: 1
:error:build org.macports.build for port gringo returned: command execution failed
:debug:build Error code: CHILDSTATUS 2733 1
:debug:build Backtrace: command execution failed
    while executing
"system -nice 0 $fullcmdstring"
    ("eval" body line 1)
    invoked from within
"eval system $notty $nice \$fullcmdstring"
    invoked from within
"command_exec build"
    (procedure "portbuild::build_main" line 8)
    invoked from within
"portbuild::build_main org.macports.build"
    ("eval" body line 1)
    invoked from within
"eval $procedure $targetname"
:info:build Warning: targets not executed for gringo: org.macports.activate org.macports.build org.macports.destroot org.macports.install
:error:build Failed to install gringo
:debug:build Registry error: gringo not registered as installed & active.
    invoked from within
"registry_active $subport"
    invoked from within
"$workername eval registry_active \$subport"
:notice:build Please see the log file for port gringo for details:
    /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_math_gringo/gringo/main.log
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