Code review comment for lp:~percona-core/percona-xtrabackup/release-2.0.6

> Are there any specific reasons to not just use "CXX=${CXX:-g++}" instead of
> introducing CXX_56?

PS 5.1 and 5.5 are compiled with gcc by default, so CXX gets exported to CXX=gcc by default. However, 5.6 won't build with CXX=gcc so we need to default to CXX=g++ for it. I created CXX_56 so we can specifically override CXX for 5.6 separately from 5.5 and 5.1.

For example in CentOS 5 we want to compile 5.1 and 5.5 with CXX=gcc44, but 5.6 with CXX=g++44.