On Sun, 4 Mar 2001, Andrew Morgan wrote:
> > I don't follow you here. How does the Linux-PAM definition give us more
> > flexibility? All I see is added complexity. If the double-pointer is
> Its been my experience that an extra layer of abstraction generally
> means more flexibility.
> If I'm a module writer, I'm not allowed to use writable static data
> since I have to watch out for the application calling pam_start()
> multiple times. But I can use static read-only data.
> I might need to do a conversation like this: {PAM_TEXT:"You need to
> re-enter your password"} {PAM_NOECHO, "password for luser: "}. With the
> Linux-PAM convention, I can build the message structure for the first
> prompt at compile time, and simply malloc a pointer array at run time.
> With the Solaris definition, I need to malloc the whole pam_message
> array structure in one go and copy in each prompt.
> If I have a variable number of prompts depending on context and I want
> to construct the conversation out of a fixed set of prompts, then I can
> mix and match with fewer memory copies than if I have to memcpy message
> arrays at run time.
Ah... Yes, I see now. Though not necessarily compelling, this capability does
offset the additional complexity. Until now it's seemed to me that the
Linux-PAM way included more hoops to jump through, but no additional
functionality.
> > for (i = 0; i < pam_prompts; i++) {
> > pmsg[i] = &msg[i];
> > }
> > into the code, whereas with the Solaris interpretation,
> > pmsg = &msg;
> > would be sufficient. I think the first method obfuscates more than it does
> This makes very little sense to me as an argument. Are you saying that
> this one module is some sort of definition of correct behavior?
My meaning was that, all things being equal, the simpler approach is
preferable. But I accept your evidence that all things are not equal here.
> How the FreeBSD folk messed this up I have no idea. They used the Linux
> codebase, and besides inheriting sample source code, they had explicit
> directions in the inherited documentation for this issue. I think you
> will find that to this day Sun has not documented its preferred behavior
> anywhere.
See my reply to Nico; I was jumping to conclusions here, and don't know with
any certainty what the behavior of FreeBSD's implementation is.
Steve Langasek
postmodern programmer
