Why does the NaCL Crypto Library source code reference header files that aren't in the code?

Question

I'm looking through the code for the NaCL Crytpo Library, though I have almost no experience with C and C++. In some of the .cpp files, there are references to header files that are not in the source code. For example, in wrapper-box.cpp it has #include "crypto_box.h" but crypto_box.h is nowhere to be found.

Why would this be and how can the library function properly with a broken reference?

Answer 1

After reading further through the documentation, the header files apparently generate themselves during compilation according to this page https://nacl.cr.yp.to/install.html as the content of the header files may vary depending on the architecture of the machine it's compiled on.