Hello,

The current add_show_from_set() uses memcpy() to clone the ``set'' 
command into a ``show'' command.  The function copies everything 
including ``set''.func(), the command's callback.

I think doing this is wrong.  The ``show'' command should only pickup 
directly relevant fields from ``set''.  Any others should be set 
separatly and explicitly.

The first problem I see is with the behavour.  The sequence:
	c = add_set_cmd (...)
	set_cmd_sfunc (c, ...)
	add_show_from_set (c)
has very different behavour to:
	c = add_set_cmd (...)
	add_show_from_set (c)
	add_cmd_sfunc (c, ...)
Only in the former case does the ``show'' command get ``set''.func().  I 
think instead a user should be expected to explicitly set 
``show''.func() vis:
	c = add_set_cmd (...)
	s = add_show_from_set (s);
	set_cmd_sfunc (s, ...)
	set_cmd_sfunc (c, ...)
or (i.e. order no longer matters):
	c = add_set_cmd (...)
	set_cmd_sfunc (c, ...)
	s = add_show_from_set (s);
	set_cmd_sfunc (s, ...)

The second problem I see is with the unintended consequences.  Because 
``show'' has silently picked up ``set''.func(), commands like ``info 
set'' call it.  For the most part this is benign.  Since the set 
variable hasn't changed, the ``set''.func() just resets everything back 
to what it was.  Only occasionally has someone noticed this 
``re-setting'' and found it necessary to ignore it (kod.c, infun.c, 
cris-tdep.c).

The attatched patch modifies the behavour of add_show_from_set() so that 
it only copies an explicit subset of the fields from the ``set'' command.

With the patch applied, I've so far found no regressions!

Thoughts?  Ok?

Andrew

PS: This change dates back to before the dawn of time (well at least to 
before Cygnus's CVS repository).