Re: Computer architects leaving Intel...

On 04/09/2024 22:53, Michael S wrote:

On Wed, 4 Sep 2024 17:25:44 -0000 (UTC)
Thomas Koenig <tkoenig@netcologne.de> wrote:
 

David Brown <david.brown@hesbynett.no> schrieb:
>

I'm all in favour of temporarily having checks for overflow (and
other errors) during debugging, but I am sceptical to having
distinct debug/release builds.  It encourages people to use debug
builds during development, bug hunting and testing, then when all
looks good they switch to release build and deploy it.  I prefer a
single build, and enable run-time checks on parts of it if and when
necessary.

>
Wise man once said...
>
# It is absurd to make elaborate security checks on debugging runs,
# when no trust is put in the results, and then remove them in
# production runs, when an erroneous result could be expensive or
# disastrous. What would we think of a sailing enthusiast who wears
# his lifejacket when training on dry land, but takes it off as soon
# as he goes to sea?
>
(C.A.R. Hoare, in "Hints on Programming Language Desin)

 Wise man was wrong.
Range check are not similar to live jackets. They do not turn incorrect
program into correct one.
 

Wise man was right.  Range checks are not intended to turn incorrect programs into correct ones - they are for damage mitigation.  Life jackets don't stop you falling overboard, they stop you drowning if you /do/ fall overboard.  The context of the quotation was "security checks", which is different from debugging and fault-finding.
For some kinds of software, you have to think about what can go wrong outside the context of software bugs, and what can be done about it - such as damage limitation.  There can be external effects such as malicious or accidental corruption of data, hardware failures, etc. These are outside the scope of C, and need special treatment such as using "volatile" to inform the compiler that something has observable behaviour, or using inline assembly or intrinsic functions for fine control.  And you have to accept that usually, there is no way to handle these things entirely in software.