Re: [boost] Current Guidance on Compiler Warnings?

Subject: Re: [boost] Current Guidance on Compiler Warnings?
From: Gavin Lambert (boost_at_[hidden])
Date: 2018-11-26 23:43:55

On 27/11/2018 12:05, Peter Dimov wrote:
> Gavin Lambert wrote:
>> As an index for a vector or array which cannot have a valid index 
>> below zero, it's perfectly fine.
> 
> It's not perfectly fine, because you can pass a negative index to it and 
> there's no way to check for that (from within the function). If you take 
> a signed type, you can assert.

You cannot pass a negative index to it without a warning at the call 
site, so you have to fix it there anyway.

Besides, in C++20 signed-unsigned integer conversion will be officially 
required to be 2s complement (and prior to this all major platforms 
implement it that way anyway).  In this case for any non-massive array 
you're fairly safe (esp. when someone fixes the call site) with a simple:

   assert(i < size());

(Whereas with a signed index you would have to also check for negative 
values.)