Does USE_GCC= 4.5+ also set C++ and Fortran to g++45/46 and gfortran45/46?

[O. Hartmann]

Using a self brewn port of a scientific software package which is 
intended to use gcc 4.5 or higher, I use "USE_GCC= 4.5+" in the top 
level Makefile. But I get an error when starting the application:

/libexec/ld-elf.so.1: /usr/lib/libstdc++.so.6: version GLIBCXX_3.4.11 
required by /usr/local/isis/3.2.1/bin/qview not found

Building the software without the ports-framework but with explicitely 
set GCC/G++/GFORTRAN results in a working binary.

My question: is USE_GCC setting C++ and Fortran compilers as desired as 
well as the C compiler?

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Thanks,
Oliver