Does wrong_type_argument return or not?

Does wrong_type_argument return or not?

[Kim F. Storm]

According to the doc string, Fsignal does not return, so
neither does wrong_type_argument.  However, looking at
Fsignal, it can return -- and the code in wrong_type_argument
definitely expects this to happen, so it can itself return
a (valid) value.

And code generally seems to expect wrong_type_argument to
return a valid value for the data which was signalled as
wrong...

However, in many places, the code does not seem to expect
wrong_type_argument to return.  

Some examples:

In data.c, Fsubr_arity and Fsubr_interactive_form both call
wrong_type_argument if the arg is not a SUBRP, but then continues
accessing it like that anyway (in case wrong_type_argument does
return).

In fns.c, concat doesn't use the return value from wrong_type_argument
(so why chekc and call it, if the errors it reports cannot happen?).

In syntax.c, check_syntax_table may call wrong_type_argument
in case of an error, but it doesn't return a value.  And
looking at the callers of check_syntax_table, I don't think
they expect it to return in case of an error.

-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk


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Re: Does wrong_type_argument return or not?

[Andreas Schwab]

storm@cua.dk (Kim F. Storm) writes:

|> According to the doc string, Fsignal does not return, so
|> neither does wrong_type_argument.  However, looking at
|> Fsignal, it can return -- and the code in wrong_type_argument
|> definitely expects this to happen, so it can itself return
|> a (valid) value.

It used to, but that has been disabled.  See the comment in Fsignal:

#if 0 /* Most callers are not prepared to handle gc if this returns.
	 So, since this feature is not very useful, take it out.  */
      /* If have called debugger and user wants to continue,
	 just return nil.  */

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE GmbH, Deutschherrnstr. 15-19, D-90429 Nürnberg
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"And now for something completely different."

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Re: Does wrong_type_argument return or not?

[Richard Stallman]

    According to the doc string, Fsignal does not return, so
    neither does wrong_type_argument.  However, looking at
    Fsignal, it can return -- and the code in wrong_type_argument
    definitely expects this to happen, so it can itself return
    a (valid) value.

Fsignal can only return in the case of a quit.  That code in
wrong_type_argument is obsolete.  Nowadays (and for about ten years),
wrong_type_argument cannot return.

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