Hi Luka,
On 16.4.2015 9:04, Luka Strižić wrote:
> Last night I examined how getopt() is used.
> Pseudo code would look something like this:
> 1) initialize optind to 0
> 2) run c = getopt_long() in a loop until c == -1
> 3) for every c set the relevant flags or execute a function, depending
> on the value of c
>
> That's perfectly fine, but when we pass, say, "-h" or "--help", most
> commands don't loop until c == -1 in step 2, but simply stop the command
> execution in step 3, before the next getopt() call.
>
> Not letting getopt() reach -1 should also be fine, because optind is
> used to store the state, and it is initialized in step 1, right?
> Well, not quite. HelenOS ported getopt from BSD (and the rest of libc?).
> There's a difference between POSIX and BSD implementation in getopt.
>
> From the BSD getopt docs:
> "In order to use getopt() to evaluate multiple sets of arguments, or to
> evaluate a single set of arguments multiple times, the variable optreset
> must be set to 1 before the second and each additional set of calls to
> getopt(), and the variable optind must be reinitialized."
> And later:
> "The optreset variable was added to make itpossible to call the
> getopt() function multiple times. This is an extension to the IEEE Std
> 1003.2 ('POSIX.2') specification."
>
> Finally, possible solutions are:
> a) Use getopt() like the docs suggest, and set optreset=1 in step 1,
> along with optind=0.
> b) Call getopt() until c==-1 in every case, without the "early" returns
> when handling c.
> c) Make optind==0 toggle an optreset=1 in getopt.c
> d) Suggestions welcome!
>
> a) and b) require changes in most bdsh commands, but a) is "the right"
> thing to do, I think. c) requires change in one file, but is a "hack".
>
> P.S. I wasn't sure where to post this, in the mailing list or the ticket
> #506 comment. I was afraid that if I posted it in the comment, not all
> people with the relevant experience might see it, so I could've
> proceeded with a "bad" a)b)c) option.
So if a) is the right thing to do (tm), how about going with option a)?
The places to fix should not be too numerous and the fix seems routinely
simple.
Jakub
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