rb_econv_check_error 2851 ext/zlib/zlib.c         rb_econv_check_error(gz->ec);
rb_econv_check_error  334 include/ruby/encoding.h void rb_econv_check_error(rb_econv_t *ec);
rb_econv_check_error 2300 io.c                               rb_econv_check_error(fptr->readconv);
rb_econv_check_error 1845 transcode.c            rb_econv_check_error(ec);