On Linux, if you compile the reducer example with -fcilk-stub to create a serialization, compilation will fail.
Closer examination of the various reducer header files revealed the following comment in several:
// Support for backwards-compatibility with Cilk 1.0 reducers.
// DO NOT USE THESE INTERFACES FOR NEW CODE
If the code to which these comments is attached in the reducer include files is commented out, then the serializations work, as long as you have a version of libstdc++ that is new enough for the cilk++ compiler installed. The reducer serialization failed on my local Red Hat system with the error message
./reducer: /usr/lib64/libstdc++.so.6: version `GLIBCXX_3.4.9' not found (required by ./reducer)
even though the cilk++ version compiled without -fcilk-stub ran fine.
I built gcc-4.2.4 (compatible with what the cilk++ installation was based upon) and put the path to the installations lib64 directory on my LD_LIBRARY_PATH and that fixed things. Your release/installation notes should indicate version requirements for libstdc++ and how to satisfy them.