On 1/5/19 6:33 AM, Russel Winder wrote:
On Sat, 2019-01-05 at 10:52 +0000, Russel Winder wrote:
On Sat, 2019-01-05 at 10:31 +0000, Nicholas Wilson via Digitalmars-d-learn
wrote:
[…]
Maybe it is a problem with copying a File_Ptr (e.g. missing a
increase of the reference count)? Like, `auto a = File_Ptr(); {
auto b = a; }` and b calls the destructor on scope exit.
That would be consistent with having problems copying to object
to pass to writeln.
I found the problem and then two minutes later read your email and bingo we
have found the problem.
Previously I had used File_Ptr* and on this occasion I was using File_Ptr
and
there was no copy constructor because I have @disable this(this). Except
that
clearly copying a value is not copying a value in this case. Clearly this
situation is what is causing the destructor to be called on an unconstructed
value. But I have no idea why.
The question now, of course, is should I have been using File_Ptr instead of
File_Ptr* in the first place. I am beginning to think I should have been.
More
thinking needed.
Switching to using File_Ptr* I now get the SIGSEGV at the end of main as you
were thinking before. Oh f###.
This code used to work. :-(
Russel, make sure your destructor both checks whether the underlying
resource is set, and clears it to invalid when freeing it.
Even types that can't be copied can be moved, or temporarily created as
rvalues. When they are moved the shell they get moved out of is still
destructed! So it has to have a state where it can be destroyed, even
though there is no resource.
Maybe some inspiration here:
https://github.com/MartinNowak/io/blob/master/src/std/io/file.d#L189-L196
-Steve
