Date: Sat, 10 Oct 2026 16:24:13 -0400
On Saturday, 10 October 2026 03:09:02 Eastern Daylight Time jim x via Std-
Discussion wrote:
> However, saying a program has undefined behaviour could imply the program
> is *unconditionally* undefined behavior; I don't think this is true.
It is true. The behaviour, *according to the Standard*, is undefined.
But machines are deterministic. Once compiled, the program will have *some*
behaviour. Data races and non-atomic accesses may have one of multiple
deterministic behaviours, but which one cannot be determined ahead of time.
That does not change the Standard. The fact that some implementation may define
a specific undefined behaviour to be very specifically determined does not remove
the fact that the Standard still said it was undefined.
Discussion wrote:
> However, saying a program has undefined behaviour could imply the program
> is *unconditionally* undefined behavior; I don't think this is true.
It is true. The behaviour, *according to the Standard*, is undefined.
But machines are deterministic. Once compiled, the program will have *some*
behaviour. Data races and non-atomic accesses may have one of multiple
deterministic behaviours, but which one cannot be determined ahead of time.
That does not change the Standard. The fact that some implementation may define
a specific undefined behaviour to be very specifically determined does not remove
the fact that the Standard still said it was undefined.
-- Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Principal Engineer - Intel Data Center - Platform & Sys. Eng.
Received on 2026-10-10 20:24:26