Bug: gcc compiler appears to handle va_arg(args, char) differently then msvc/clang-cl

Description:

When compiled with the gcc compiler, the following line generates a warning:

    buffer << va_arg(args, char);

    warning: 'char' is promoted to 'int' when passed through '...'

    note: if this code is reached, the program will abort

No such warning appears when compiling with MSVC or clang-cl, so I'm assuming there's a difference in how '...' arguments are added to va_list. If it is different, then this will need conditional code to handle.