[bug #59973] [PATCH] implement .soquiet and .msoquiet requests

[G. Branden Robinson]

Update of bug #59973 (project groff):

                  Status:               Need Info => In Progress            

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Follow-up Comment #5:

Hi Dave,

[comment #3 comment #3:]
> Your "while" (non)loop expressed in pseudocode is:
> 
>       while (1) {
>        if (A)
>          if (B)
>            break;
>        error(...);
>        break;
>       }
> 
> Neither "if" having an "else," this should be equivalent to:
> 
>       while (1) {
>        if (A && B)
>          break;
>        error(...);
>        break;
>       }
> 
> This further seems to be equivalent to the lower-level pseudocode:
> 
>        if (A && B)
>          goto NEXT;
>        error(...)
>        goto NEXT;
>       NEXT:
> 
> which basically reduces to:
> 
>       if !(A && B)
>         error(...)
> 
> I confess I'm no C++ coder, so I could be overlooking any number of
language-specific gotchas.  And I don't know what you mean by "complicating
the boolean conditional afterward," the thing you were trying to avoid.  But
naively tracing the code path, I don't understand the need for the "while" at
all.

You are completely correct.  I suspect, and an indentation error on the same
reinforces this, that I had something even more complicated originally.

I've refactored to:

if (!(quietly && (ENOENT == errno)))

One could of course apply De Morgan's Law here, but I think the intent is
clearer this way.

As you can see, I've also chosen not to worry about EACCES at this point. 
This facilitates further simplification of the logic--and, as you note, that
error might indicate something actually unexpected.

If we ever need to handle other POSIX errno symbols, I would extend the
request to take a list of such strings.  In fact, .so and .mso themselves
could be extended in this way... But I do not do so at present because I don't
know if there is demand for such a feature.  This one has 2 practical use
cases as noted in the original ticket.

Next, update the documentation for these new requests.

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