start-process: nil check on arg program

start-process: nil check on arg program

[Tino Calancha]

Hi,

this is a question about
* lisp/subr.el (start-process)

I don't see the point for the nil check on program.

* program is a mandatory argument: if program is missing, for instance
(start-process "foo" "buf")
before the check run you already get a
'Wrong-number-of-arguments' error.

* If program is nil, for instance,
(start-process "foo" "buf" nil)
which IMO it shouldn't ever happend, that check don't
prevent the creation of a useless process.


I guess the nil check for program should be before the call to `apply'
(as in following patch) or not be included at all.
What do you think?

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
diff --git a/lisp/subr.el b/lisp/subr.el
index 8ab1178..632a9e6 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2003,10 +2003,10 @@ start-process
  one of them using the shell syntax."
    (unless (fboundp 'make-process)
      (error "Emacs was compiled without subprocess support"))
-  (apply #'make-process
-	 (append (list :name name :buffer buffer)
-		 (if program
-		     (list :command (cons program program-args))))))
+  (when program
+    (apply #'make-process
+           (append (list :name name :buffer buffer
+                         :command (cons program program-args))))))

  (defun process-lines (program &rest args)
    "Execute PROGRAM with ARGS, returning its output as a list of lines.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

Tino

Re: start-process: nil check on arg program

[Andreas Schwab]

On Aug 25 2016, Tino Calancha <tino.calancha@gmail.com> wrote:

> * If program is nil, for instance,
> (start-process "foo" "buf" nil)
> which IMO it shouldn't ever happend, that check don't
> prevent the creation of a useless process.

nil is explicitly documented as a meaningful argument.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: start-process: nil check on arg program

[Tino Calancha]

On Thu, 25 Aug 2016, Andreas Schwab wrote:

> On Aug 25 2016, Tino Calancha <tino.calancha@gmail.com> wrote:
>
>> * If program is nil, for instance,
>> (start-process "foo" "buf" nil)
>> which IMO it shouldn't ever happend, that check don't
>> prevent the creation of a useless process.
>
> nil is explicitly documented as a meaningful argument.
You are right. Thanks!
Maybe in my example has no much sense, i mean, just
(start-process "foo" "buf" nil)
but with additional arguments,
i.e.
(start-process "foo" "buf" nil args)
it might have sense.

Re: start-process: nil check on arg program

[Andreas Röhler]

On 25.08.2016 08:58, Tino Calancha wrote:
>
>
> On Thu, 25 Aug 2016, Andreas Schwab wrote:
>
>> On Aug 25 2016, Tino Calancha <tino.calancha@gmail.com> wrote:
>>
>>> * If program is nil, for instance,
>>> (start-process "foo" "buf" nil)
>>> which IMO it shouldn't ever happend, that check don't
>>> prevent the creation of a useless process.
>>
>> nil is explicitly documented as a meaningful argument.
> You are right. Thanks!
> Maybe in my example has no much sense, i mean, just
> (start-process "foo" "buf" nil)
> but with additional arguments,
> i.e.
> (start-process "foo" "buf" nil args)
> it might have sense.
>

Don't understand the additional arguments here at stake:
Doku says WRT program-slot in question:

If nil, just associate a pty with the buffer.