printf without any argument exits ash

[Michael Abbott]

I meant to send this last week.

On Wed, 10 Dec 2008, Denys Vlasenko wrote:
> > But, when I run "printf" without any argument, it simply kills the shell
> http://busybox.net/downloads/fixes-1.13.1/busybox-1.13.1-printf.patch

A couple of thoughts:

1. This patch needs to be added to the 1.12 patches (it applies cleanly to 
1.12.3 without any modification).  Except...

2. Eww.

Clearly the problem is that bb_show_usage() exits after showing applet 
specific usage, but when it's called as a built-in from a shell this isn't 
the right behaviour.  

I see, for example, that rm.c also claims to be a NOFORK applet (shouldn't 
printf.c say so as well?), but it happily manages to call bb_show_usage() 
without killing the shell.  Or is it lying about not being forked...?

Sorry, I should be answering my own questions by inspecting the code -- 
but I don't know my way around well enough.  For example, where is the 
FORK/NOFORK status determined?

A quick dig is interesting.  If I take rm.c at face value, there's an 
interesting discrepancy.  `rm` definitely shows usage without exiting 
the shell, and clearly does so by calling bb_show_usage(), which 
clearly exits by calling xfunc_die() ... which is where things get 
interesting.  I'm not too sure about the context, but it looks to me as if 
we *should* be exiting by a longjmp (which is what I was expecting).

Thus this begs the question: why didn't printf take the longjmp?  Surely 
the patch should address that underlying problem rather than the nasty 
local hack which we actually see!