An initial revision of "kill -l [exitstatus]"

[Mats Erik Andersson]

Hi there,

let me return to the subject of "kill -l", as it is present
in an ash builtin and as an applet. Luciano M. F. Rocha had
an important point earlier on, when observing that the ash
builtin command must supply a functionality "kill -9 %1",
which the applet "kill" can never do. Therefore I have as a
first step, in response to Denis Vlasenko's challenge to
integrate the two kill commands into a single code,
concentrated on a partial task:

	1) Make a shared code for "kill -l [exitstatus]".

	2) Conform to all parts of SUSv3 for "kill -l [exitstatus]"

Both these are accomplished using the two attached files. They are not
intended to immediately be applied to the source tree, since they have
two macros
	ENABLE_FEATURE_KILL_STRICTLY_SUSV3
and
	ENABLE_FEATURE_KILL_MANY_SIGNALS

defined internally, but they are functional on my testing system
and they save 235 bytes, in addition to complying to SUSv3, which both
the earlier kill-instances fail to do. I would like comments on these
snippets. My implementation presently touches upon the files

	libbb/signallist.c    (new builtin/shared functionality)
	libbb/Kbuild
	include/libbb.h
	procps/kill.c
	shell/ash.c
	

Our earlier discussion on "kill -l exitstatus" did not properly fathom
what the standard intends with this. I have been studying this and
believe I know their intention. SUSv3 would like this functionality:

$ cat > /dev/null
<Ctrl-C>
$ echo "Died of SIG$(kill -l $?)"
Died of SIGINT
$

The actual value of "$?" is 130 when evaluated in the above situation.
My code correctly delivers this functionality, where both the previous
kill-instances aborted with an error, since 130 is not an allowed signal
in their implementation.

As a minimal extension on SUSv3, my code allows a bidirectional
conversion, where SUSv3 is uni-directional:

$ kill -l 3    # Required by SUSv3
QUIT
$ kill -l QUIT
3


I hope to hear your views and criticism in due time.

Best regards,    Mats E Andersson
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