Path: utzoo!attcan!uunet!zephyr.ens.tek.com!tektronix!nosun!qiclab!m2xenix!puddle!f101.n273.z1.fidonet.org!Peter.M..Perchansky
From: Peter.M..Perchansky@f101.n273.z1.fidonet.org (Peter M. Perchansky)
Newsgroups: comp.lang.modula2
Subject: Re: JPI M2 2.00 - PROCEDURE FUNCTIONS & ERROR CHECKING
Message-ID: <2607.26B7D08F@puddle.fidonet.org>
Date: 30 Jul 90 14:52:04 GMT
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Hello David:

In a msg dated 26 Jul 90  01:12:39, David Hinds said:
**********************BEGIN QUOTE*****************************

From: dhinds@portia.Stanford.EDU (David Hinds)
Date: 24 Jul 90 06:05:19 GMT
Organization: AIR, Stanford University
Message-ID: <1990Jul24.060519.23417@portia.Stanford.EDU>
Newsgroups: comp.lang.modula2

    I would be very surprised to see a compiler that flagged the
above
routine as an error.  I don't think that leaving the possibility
of
reaching the end of a procedure without a RETURN statement
violates the
syntax of M2 - am I wrong?  If I'm right, then there is no way
for the
compiler, in the general case, to determine if the illegal exit
might
ever be executed.  Sure, it could test for some trivial cases
like the
one in the example, but it seems pointless.  The runtime trap
can catch
infinitely more cases of illegal exits than the compiler ever
could.  I
guess the compiler could easily enough make sure that a
procedure has
at least one RETURN statement that could be reached, but beyond
that,
the problem is insurmountable. A compiler could require that all
execution
paths end in RETURN statements, but that is still a non-trivial
extension
to the language syntax.
***********************END QUOTE******************************

    JPI TopSpeed Modula-2 1.17 issued a compile-time error; so it is possible.

    JPI TopSpeed Modula-2 2.00 issues a run-time error.



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