Walter Bright wrote:
On 2/18/2012 3:13 PM, Andrei Alexandrescu wrote:
On 2/18/12 4:26 PM, Jonathan M Davis wrote (abridged):
GetOptException
FlagArgumentMissingException
InvalidFlagArgumentException
UnknownFlagException
FileException
FileNotFoundException
NotFileException
NotDirException
AccessDeniedException
I died inside a little.
I think typed exceptions are a good idea, but something looks wrong with
these.
(Also, having a large number of exception types is going to produce a
lot of program size bloat. Remember, for EVERY class type, you've got
the vtbl[], the .init data, and the TypeInfo. Going to town on exception
types can really add this up.)
I feel that druntime might be optimized.
1) I think most of the bloat comes from .init data. For example this
program:
class A
{
ubyte[1024 * 1024 * 10] tenMegabytes;
}
class B : A {}
class C : B {}
class D : C {}
void main() { }
compiles to 40 MB exe under windows. Every class has copy of the same 10
MB .init data.
I wonder why init is byte[] array. IMHO the better thing would be making
it byte[][], i.e. array of byte arrays. Then some derived parts may be
shared as byte array slices. This maybe little slower because it adds
another level of indirection.
By the way, current byte[] array solution doesn't speed up void
initializers, because it always overwrites void fields. This simple program:
import std.stdio;
class A { ubyte[8] test = void; }
void main() { writeln((new A()).test); }
always prints [0, 0, 0, 0, 0, 0, 0, 0].
With byte[][] array, some slices may have null ptrs so they may be
initialized using memset() or not initialized at all (when using void
initializer).
2) vtbl[] might also be shared for derivation chains that don't override
any functions. But that may slow down program start, because vtables
must be constructed at runtime.
Please correct me if I'm wrong :) I think that the use of classes should
not be limited because of implementation issues. For me it's purely
implementation issue, and I suppose it may be addressed with more
optimized ABI or druntime.
