Re: [PATCH] Clear up perlcritic 'missing return' warning

From: Mike Blackwell <maiku41(at)gmail(dot)com>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCH] Clear up perlcritic 'missing return' warning
Date: 2018-05-22 20:35:10
Message-ID: CAESHdJoFenPdc=XfrzM5m9wCGqfHEbum0eQ4UwYRDGw+8vxOyA@mail.gmail.com
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On Tue, May 22, 2018 at 3:32 AM, Michael Paquier <michael(at)paquier(dot)xyz>
wrote:

>
> <snip> And this
> maps with any C code.
>

The important differences here are:
*) Declaring a C function as void prevents returning a value. The intent
not to return a value is clear to any caller and is enforced by the
compiler. There is no equivalent protection in Perl.
*) Falling off the end of a C function that returns a type other than
void has undefined results. Perl will always return the value of the last
statement executed.

Because Perl does allow returning a value without explicitly using return,
it's easy to write code that breaks if an unwary person adds a line to the
end of the subroutine. There's a common constructor incantation that has
this problem. It's a real gotcha for C programmers just starting to poke
around in Perl code.

This difference also allows users of .pm modules to abuse the API of a
method intended to be "void", if the value returned falling off the end
happens to seem useful, leading to breakage if the method's code changes in
the future.

> This is most likely going to be forgotten.
>

That's what perlcritic is for. :)

Mike

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