dmd foreach loops throw exceptions on invalid UTF sequences, use replacementDchar instead

[Abdulhaq]

On Friday, 5 November 2021 at 10:09:40 UTC, norm wrote:
>
> It isn't always that simple, e.g. working on medical devices 
> crashing isn't an option when it comes to how we're going to 
> deal with bad data.

Mm, I have a totally different take on this. In my view all 
incoming data should be sanitised on entry into the application, 
this takes place at what I think of as leaf nodes in the 
application. This sanitisation includes conversion of all 
measurements into standard units, checking validity of strings 
etc.

Once data has entered the main application then the application 
should **fail fast**. This is **especially important** for 
medical devices. This allows the developers of the application to 
see, early in development, problems with their code and the logic 
thereof.

Signs of developers ignoring the fail fast principle include a 
disease I've identified where ```if (x is null)``` is seen to 
start proliferating through the code. This happens when you are 
calling a function that you did not write and one day you find it 
has returned null, you don't know why. So you add an ```if (null) 
return null``` to your code and carry on. This allows the program 
to stagger on in the face of being in a state that is not 
understood by the developer.

If I am on a ventilator and the program enters a state that the 
programmer did not anticipate, then life can start to get very 
uncomfortable for me. I would far prefer that it stopped, coughed 
up an error code, and the medical staff can unplug it and 
(quickly, I hope) replace it with another one. If there is 
actually a scenario where staggering on is considered better, 
then at the very least it should be under instruction from the 
programmer. The idea of the language runtime silently modifying 
application data is somewhat frightening for me in this scenario.