Hi,
Did you build it from the official tarbal archive?
Have you compiled the example without any source code modification?
What is your compiler, librarian and linker settings?
Share your "Command line" for the library and the application if you
added a VS project.
Can you share the content of 'base64' and 'base64_len' parameters,
when MHD_base64_to_bin_n() is called and then aborted with run-time
check?
Probably VS compiler requires an extra casting, while in practice the
code has enough castings already.