Thoughts from newcommer

[Jonathan M Davis via Digitalmars-d]

On Monday, April 17, 2017 11:14:47 Shachar Shemesh via Digitalmars-d wrote:
> scope(exit) is a much cleaner solution than a finally clause, but
> not as clean as RAII. If the language supports RAII, how come
> people are not using it?

Well, if you're talking managing memory, most folks just use the GC. And for
the rest, I think that RAII does get used fairly frequently (e.g.
std.stdio.File uses it), but largely, RAII is only going to get used when
some resource is going to need to be passed around or managed in the same
way in several places, because otherwise, it's simpler to just put a
scope(exit) statement in there than to declare a type. And the programs that
do use RAII are simply buggy in the cases where constructors don't clean up
properly when an exception is thrown. For a lot of code, it really doesn't
matter (e.g. they simply aren't at any real risk of an exception being
thrown during construction), and even in code where it does matter, it could
easily be missed, especially if exceptions aren't thrown often. Certainly,
this topic comes up infrequently enough that I really don't think that all
that many folks are using scope(exit) instead of RAII simply because of the
bug with constructors. I'd guess that most folks aren't even aware that it's
an issue.

Now, I totally agree that https://issues.dlang.org/show_bug.cgi?id=14246 is
a serious issue that needs to be fixed and that some software is going to
have some major issues as long as it uses RAII and that bug exists. But
because D does not rely as heavily on RAII as C++ does, and RAII works
correctly in many cases (particularly if an exception is not thrown during
construction), a lot of code can be written which happens to use RAII
without being buggy or without the bug being caught. It's when you start
relying heavily on RAII that you're more likely to notice it. If RAII were
completely broken, I suspect that this would have been a higher priority and
would have been fixed ages ago. But because RAII mostly works, this problem
has managed to go sufficiently under the radar that it's never become as
high a priority as it arguably should be, and it hasn't yet been fixed like
it should have been.

- Jonathan M Davis