ecerr_source_encoding_name 4560 transcode.c        rb_define_method(rb_eUndefinedConversionError, "source_encoding_name", ecerr_source_encoding_name, 0);
ecerr_source_encoding_name 4566 transcode.c        rb_define_method(rb_eInvalidByteSequenceError, "source_encoding_name", ecerr_source_encoding_name, 0);