Hi everyone,
There's a little problem. I've written a program in order to connect to the mongodb cluster Atlas and changed some values.
Than I've installed the mongoc driver versioned 1.16.2 and the version of mongocxx driver from the master branch.
The commands for mongoc driver are:

cd cmake-build
cmake -G "Visual Studio 16 2019" \
    "-DCMAKE_INSTALL_PREFIX=C:\mongo-c-driver" \
    "-DCMAKE_PREFIX_PATH=C:\mongo-c-driver" \
    ..

"path-to-msbuild\msbuild.exe" ALL_BUILD.vcxproj  - debug
"path-to-msbuild\msbuild.exe" "/p:Configuration=RelWithDebInfo" ALL_BUILD.vcxproj - release
"path-to-msbuild\msbuild.exe" INSTALL.vcxproj

The commands for mongocxx driver are:

cmake .. \
     -G "Visual Studio 16 2019"           \
    -DBOOST_ROOT=C:\boost_1_60_0          \
    -DCMAKE_PREFIX_PATH=C:\mongo-c-driver       \
    -DCMAKE_INSTALL_PREFIX=C:\mongo-cxx-driver

"path-to-msbuild\msbuild.exe" ALL_BUILD.vcxproj
"path-to-msbuild\msbuild.exe" INSTALL.vcxproj

I've changed .vcxproj, in accordance with this instruction — "Compiling with MSVC"  http://mongocxx.org/mongocxx-v3/installation/
for DEBUG/RELEASE x64
My program has worked as it should, with debug versions of drivers, until the last version was released. After last release, it has started to catch an bad_alloc exception.
Maybe I did something wrong? Maybe I've used wrong VS version?
env:
cmake 3.17.0-rc3
VS 2019
mongoc driver 1.16.2
mongocxx driver from github master branch

regards, max