Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: Bo Persson <bo@bo-persson.se>
Newsgroups: comp.lang.c++
Subject: Re: overuse of auto is dangerous
Date: Fri, 13 Mar 2020 03:17:54 +0100
Lines: 39
Message-ID: <hd08qjFilvfU1@mid.individual.net>
References: <r4eghj$j17$1@dont-email.me>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Trace: individual.net njdW9EWFXENfLTt2dR1rMAgspcLdUHr5Fg1Q9WSEkJC9p1mPrY
Cancel-Lock: sha1:NkhQ4BbWFQwP1PDbsTeboy4ss+k=
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0
In-Reply-To: <r4eghj$j17$1@dont-email.me>
Content-Language: sv
Xref: csiph.com comp.lang.c++:72250

On 2020-03-13 at 00:27, jacobnavia wrote:
> Consider:
> 
> auto f = foo();
> 
> What is "f"?

Easy, "f" is the return value of foo(). Probably some kind of iterator 
that you are just going to pass to one or more std::algorithm, so you 
don't really care to spell out its name.


> 
> Ahhh you have to figure out the return type of foo() of course. Great, 
> there you go to your favorite IDE and try to jump to the correct 
> definition of the foo() method in the correct class with the correct 
> overload resolution...
> 
> Even worst... when you change the return type of foo() from type A to 
> type Z, all the "auto" constructs will continue to compile AUTOmatically 
> of course. Problem is, the type of "f" will have changed and that can 
> provoke incomprehensible compile time errors further down or even run 
> time errors in the form of access violation or whatever!
> 
> Wouldn't it be better to write:
> 
> TYPE_A F = foo();


You mean like

typename std::unordered_map<key, data, std::hash<key>, 
std::equal_to<key>, special_allocator<std::pair<const key, 
data>>>::const_iterator F = foo();


    Bo Persson