g2ctl doesnt set the proper undefined value

[P.R.]

Hi,
Im having an issue with g2ctl & how it sets the undefined value in the ctl
file output.
g2ctl.pl hard-sets the undef value at 9.99e+20, which I *believe* has been
pretty much the standard undef value up until now.

However, the undef value on some datasets (the GFS grib2 files, for example)
is giving me a value of -9.99e+08.
(could someone please confirm this value for undef from the GFS grib2
files?).

Normally, I don't believe that it matters if the g2ctl.pl undef value
differs from the grib2's undef value.
However, I ran into an issue with pygrads; pygrads reads the undef value
from the ctl file, and it will improperly try to plot undefined data points
due to fact that it doesn't know the correct undef value.

So, my question/suggestion is:
should g2ctl be setting the undef value based on the dataset inside the
grib2 file, instead of hard-setting to a fixed value?
Is it even possible to retrieve this value from the grib2 metadata?

Thanks,
P.Romero