On Tuesday, 20 January 2015 at 18:12:27 UTC, ketmar via
Digitalmars-d wrote:
Hello.
as there is no possibility to doing GC allocations in class
destructors, wouldn't it be nice to just force "@nogc"
attribute on
such dtors?
Classes don't have to be designed to be allocated on the GC heap.
Class instances can be allocated on the stack, the C heap, or
anywhere else.
i know, i know, "this will break alot of code". i'm pretty sure
that
this will break alot of INVALID code, which better be broken at
compile-time anyway.
There is potentially a plethora of valid code broken by such a
change:
* Classes designed to be used on the stack or other non-GC-heap
memory locations.
* Class destructors that never call a GC function, but @nogc was
nevertheless not applied throughout the codebase, maybe because
it was an old or poorly maintainable codebase.
* Users using non-standard or modified GC implementations that
don't have this restriction.
* Classes in programs that have ripped out the GC to begin with,
replacing `new` and other GC primitives with something else. This
one is dubious, as from a language standpoint, `new` is
exclusively intended for GC allocation.
* Class destructors calling into functions that predictively
have both an allocating and non-allocating path, thus cannot be
@nogc but can be verified at the call-site to be @nogc. Arguably
such functions are poorly designed and should be split into two
layers.
let's see how this proposal will be rejected. will there be
some sane
reasons, or only the good old song about "broken code"? make
your bets!
D is a systems-programming language and should cater to a wide
variety of use patterns, including users who wish to use classes
in non-GC memory locations. Perhaps splitting class destructors
into two separate concepts, a destructor and a finalizer, with
the latter being @nogc, could be a more satisfactory solution.
Alternatively, maybe we should anticipate a standard GC
implementation (or one of several standard implementations, like
Java and .NET do) that does not have this restriction.
