On Wednesday, 5 August 2015 at 10:31:40 UTC, Iain Buclaw wrote:
I think as a guideline, there are really only be two places
where using an assert makes sense in druntime/phobos.
1. Internal modules, such as rt and core.internal.
2. Inside contracts (in, out, invariant) or unittests.
Everywhere else - *especially* if it's part of a public API
like core.time - you should throw an Exception or Error based
on what you see fit.
I think that it makes perfect sense to use assertions inside of
druntime or Phobos functions when testing the correctness of
their internal state, but it obviously can't be expected that
they run normally (at least in non-templated code), and it can't
be expected that much beyond the unit tests run them (at least in
non-templated code), since almost no one is going to be using a
debug version of druntime/Phobos. Certainly, I don't see anything
special about druntime or Phobos with regards to assertions
except for the fact that not much beyond the unit tests is going
to be using druntime/Phobos in debug mode, so assertions in
non-templated code simply aren't going to be doing anything
outside of the unit test builds.
As for assert(0) specifically, it makes sense in cases where the
code should never ever hit that point, and there's a serious
problem if it does (e.g. the default branch of a switch statement
where it should be impossible for that branch to be hit), but it
was a mistake to use it in core.time, since that was failing
based on a system call returning a failure (which should
basically never happen in this case, but it still depends on the
environment and thus could conceivably fail as opposed to only
ever failing if druntime's code is definitely broken).
Because of this view, I'm not really in agreement with the
addition of a core.abort module.
Well, then please comment on the PR:
https://github.com/D-Programming-Language/druntime/pull/1337
It seems to me that the whole point of abort is to work around
the fact that Walter doesn't want assert(0) to print messages
before the HLT instruction in release mode. Certainly, I can't
see any other reason for it.
- Jonathan M Davis
