Re: [PATCH] xen: let ASSERT_UNREACHABLE() WARN() in non-debug builds

[Juergen Gross <jgross@xxxxxxxx>]

On 24.08.22 12:35, Jan Beulich wrote:
> On 24.08.2022 12:22, Juergen Gross wrote:
> > Hitting an ASSERT_UNREACHABLE() is always wrong, so even in production
> > builds a warning seems to be appropriate when hitting one.
> I disagree, for two reasons: This violates the implication of NDEBUG
> meaning ASSERT() and friends expand to no actual code. Plus if doing so
This is something we can change IMHO.

> for ASSERT_UNREACHABLE(), why would we not do the same for ASSERT()?
There are multiple reasons to have ASSERT()s. Some serve as a kind of
documentation (e.g. to document that the programmer thought of a special
case not being possible), or they are meant to catch hard to diagnose
bugs rather early instead of letting them hit later in a situation where
it wouldn't be clear what caused them. Adding a WARN() for all of these
cases isn't really appropriate, especially as this might impact
performance due to added tests, which isn't the case for theoretically
unreachable code.

> There's a reason we have ASSERT() and friends and, independently,
> WARN_ON() / BUG_ON() et al.
We might want to introduce something like ASSERT_OR_WARN(). I'm sure
this could be useful in some cases.


Juergen

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