Unknown language 'cpp' specified, please use one of:
all, abc, actionscript, ada, asm, c, c#, c++, caml, cmake, cobol, conf, css, d, diff, docbook, erlang, f77, ferite, forth, fortran, freebasic, genie, glsl, haskell, haxe, html, java, javascript, latex, lisp, lua, make, markdown, matlab, nsis, pascal, perl, php, po, python, r, rest, ruby, scala, sh, sql, tcl, txt2tags, vala, verilog, vhdl, xml, yaml
See the help page for usage information.