GCC 4.6.x pre-dates support for the C++11 standard so does not provide
-std=c++11. It anticpates C++11 experimentally and provides
to enable that experimental support.
-std=c++11 is first available in
GCC 4.7.x. If you cannot upgrade to a more recent compiler then change
Contd. for OP's comments
Perhaps you have not read the
INSTALL.TXT file of the
Before building HElib, you may want to look at the Makefile, and
consider adjusting some of the defaults for CC and CFLAGS. The
defaults should be OK on most systems, but you can see the suggested
options, which are documented in the Makefile.
Following this advice, edit
CFLAGS = -g -O2 -std=c++11 -pthread -DFHE_THREADS -DFHE_DCRT_THREADS -DFHE_BOOT_THREADS
Be aware that the project is not guaranteed to build successfully with gcc 4.6.3
- a very old compiler version - after this change; but without making this change gcc 4.6.3 cannot be used with any degree of C++11 support at all.
You have not given any reason for using such an old compiler.