During compilation on OSX 10.15.6, using XCode 11.6 (clang 11.0.3), the build fails on options/auto_encryption.cpp and options/client_encryption.cpp, with the usual template vomit specific to a missing <string> header.

Relevant flags in use are:

CC=clang

CXX=clang++

CXXFLAGS="-std=c+17 -stdlib=libc+"

-DBSONCXX_POLY_USE_STD=1

-DCMAKE_CXX_STANDARD=17

Adding an include for <string> to options/auto_encryption.hpp and options/client_encryption.hpp allows the build to proceed. Probably not the optimal solution, but it worked for us.