grub-mkrescue reacts vaguely on xorriso problems

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

on occasion of

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=864701
  "grub-common: grub-mkrescue does nothing, successfully"

i wonder whether the reaction of grub-mkrescue on xorriso problems
is intended and appropriate. E.g. with:

  grub-mkrescue -o output.iso SOURCE

--------------------------------------------------------------------------

If xorriso is missing, then grub-mkrescue reports

  grub-mkrescue: warning: Your xorriso doesn't support `--grub2-boot-info'. Some features are disabled. Please use xorriso 1.2.9 or later..

and returns exit value 0.
I.e. it does not say that xorriso does not work at all and it does not
indicate the failure to its caller.

I understand from
  http://git.savannah.gnu.org/cgit/grub.git/tree/util/grub-mkrescue.c#n571
that the warning is only emitted if the ISO gets prepared for x86 BIOS.
So in other cases the run might be totally silent (did not test).

Several distros ship grub-mkrescue in packages which do not mandatorily
depend on xorriso. So a clearer message from upstream about the necessity
of xorriso seems desirable.

--------------------------------------------------------------------------

If xorriso is executable and of sufficient version but the user makes a
mistake with grub-mkrescue argument SOURCE (or with some added xorrisofs
options), then xorriso aborts with e.g.

  xorriso : FAILURE : Cannot determine attributes of source file '...' : No such file or directory
  ...
  xorriso : aborting : -abort_on 'FAILURE' encountered 'FAILURE'

no ISO image emerges but grub-mkrescue exits with value 0.

A xorriso batch run returns exit value 5 if it aborts due to the -abort_on
threshold. But grub-mkrescue ignores the exit value of xorriso in
  http://git.savannah.gnu.org/cgit/grub.git/tree/util/grub-mkrescue.c#n963

--------------------------------------------------------------------------

Have a nice day :)

Thomas