Warp is an open-source tool developed in D language to replace the original cpp (understand CPreProcessor, not C PlusPlus) when compiling C or C++ source code.

The main goal is productivity improvement, thanks to faster preprocessing. And for that, Warp relies on caching to achieve better preprocessing times.

Read this interview between Andrei Alexandrescu a Research Scientist at Facebook, and Walter Bright, the writer of Warp (these two guys are also the creators of the D language).