message: Document that LLDB_LOG macros use the format_providers.
diff: @@ -206,6 +206,26 @@ private:
  } // namespace lldb_private
  +/// The LLDB_LOG* macros defined below are the way to emit log messages.
  +///
  +/// Note that the macros surround the arguments in a check for the log
  +/// being on, so you can freely call methods in arguments without affecting
  +/// the non-log execution flow.
  +///
  +/// If you need to do more complex computations to prepare the log message
  +/// be sure to add your own if (log) check, since we don't want logging to
  +/// have any effect when not on.
  +///
  +/// However, the LLDB_LOG macro uses the llvm::formatv system (see the
  +/// ProgrammersManual page in the llvm docs for more details). This allows
  +/// the use of "format_providers" to auto-format datatypes, and there are
  +/// already formatters for some of the llvm and lldb datatypes.
  +///
  +/// So if you need to do non-trivial formatting of one of these types, be
  +/// sure to grep the lldb and llvm sources for "format_provider" to see if
  +/// there is already a formatter before doing in situ formatting, and if
  +/// possible add a provider if one does not already exist.
  +
  #define LLDB_LOG(log, ...) \
  do { \
  ::lldb_private::Log *log_private = (log); \
  