All versions of gnuplot that I have tried (4.2 - 4.7) give unreasonable results for the following sequence of commands
set log y
set ytics 20
It extends ymax to 10^20 rather than to the next multiple of 20. It doesn't seem to extend ymin at all. This is clearly wrong, but what exactly should it do instead? Should it just ignore range extension for log-scaled axes? The simple-minded fix of applying AXIS_LOG_VALUE in the round_out() routine produces a more reasonable bound for ymax in this particular case, but blows up in evaluating ymin whenever the extension would reach 0.