assert(0) behavior

[Jonathan M Davis via Digitalmars-d]

On Tuesday, 4 August 2015 at 22:13:40 UTC, Steven Schveighoffer 
wrote:
> On 8/4/15 5:39 PM, Jonathan M Davis wrote:
>
>> I'm certainly not opposed to have a message be printed before 
>> the HLT
>> instruction with assert(0), but I don't at all agree that the 
>> fact that
>> the message is not seen in -release is a reason not to have a 
>> message.
>
> For instance:
>
> https://github.com/D-Programming-Language/druntime/blob/master/src/core/time.d#L2283
>
> This makes it seem like a message will be printed in the case 
> where ticksPerSecond was 0. but in reality it simply throws a 
> segfault.
>
> Whether this happens or not in debug mode is pretty much 
> irrelevant -- druntime is used in release mode by the vast 
> majority of all developers, and this passes unit tests for us. 
> It's the whole impetus for this thread, because someone 
> actually did find a case where it gets there.
>
> So why have a message with the clock name that failed? Why not 
> just assert(0)? The only purpose I see for such a message is to 
> trick the reviewer into accepting it (not that this was the 
> intention of course) as being sufficiently explanatory when an 
> error occurs.
>
> We should always review such code with the view that when it 
> *doesn't* print the message, is the error sufficient to a user 
> such that they know where to look. I find it hard to believe 
> it's *ever* sufficient, if you needed to have a message in the 
> first place.
>
> We can look at it this way -- if you need to add a message to 
> an assert(0) for it to make sense, you should find a different 
> way to communicate that.

It was never expected that a user to see any of those messages 
anyway. The idea was that if they failed, there was something 
seriously wrong, and the program needed to be killed. If the 
message prints when it fails, great. It's more explanatory that 
way, but it's a bonus (and one that you do get if druntime is 
build in debug mode). The purpose was to kill the program, 
because it was in an invalid state.

- Jonathan M Davis