This problem exists when compiling in VSCode/PlatformIO.
Workaround:
Edit cpp-base64\base64.cpp, within function pos_of_char()
Comment out:
throw std::runtime_error("Input is not valid base64-encoded data.");
Add:
return 0;
Delete cpp-base64\test.cpp and cpp-base64\test-google.cpp
On systems with exception disabled current code is not able to compile. Replace throw with assert in such systems.