See also this post to D.learn by Lodovico Giaretta:
http://forum.dlang.org/post/[email protected]
----
import std.typecons: RefCounted;
struct S
{
int x;
RefCounted!S s;
}
void main()
{
S s;
s.x = 1;
s.s.x = 2;
s.s.s.x = 3;
assert(s.x == 1);
assert(s.s.x == 2);
assert(s.s.s.x == 3);
}
----
2.067.1: Compiles and passes asserts.
2.068.2, 2.069.2: segfault
2.070.2, 2.071.0: "no size yet for forward reference" errors
git master (bc74f4a): "std/typecons.d(4739): Error: forward reference to (*this._store)._payload"
Marking this as a phobos regression. I have a reduction, but that works up to 2.069, so there may be something else going on. Filing that separately.
Comment #1 by ag0aep6g — 2016-05-10T21:59:08Z
(In reply to ag0aep6g from comment #0)
> Marking this as a phobos regression. I have a reduction, but that works up
> to 2.069, so there may be something else going on. Filing that separately.
Filed as issue 16012.
Compiling this now gives the following error:
[email protected](380): Assertion failure
----------------
0x005FD23F in _d_assertp
0x00408EFA in AttribDeclaration at C:\cbx\mars\attrib.d(181)
0x0045F5D7 in StructDeclaration at C:\cbx\mars\dstruct.d(373)
0x0045F5D7 in StructDeclaration at C:\cbx\mars\dstruct.d(373)
0x00474D79 in TemplateInstance at C:\cbx\mars\dtemplate.d(8272)
0x00474DDC in TemplateInstance at C:\cbx\mars\dtemplate.d(8290)
0x00470E61 in TemplateInstance at C:\cbx\mars\dtemplate.d(6361)
0x004714BB in TemplateInstance at C:\cbx\mars\dtemplate.d(6595)
0x004ECA1E in TypeInstance at C:\cbx\mars\mtype.d(8004)
0x004ECAE2 in TypeInstance at C:\cbx\mars\mtype.d(8027)
0x00434BE8 in VarDeclaration at C:\cbx\mars\declaration.d(1180)
0x0045F5D7 in StructDeclaration at C:\cbx\mars\dstruct.d(373)
0x00454D54 in Module at C:\cbx\mars\dmodule.d(1065)
0x004D9F9F in int ddmd.mars.tryMain(uint, const(char)**) at C:\cbx\mars\mars.d(847)
0x004DAB43 in _Dmain at C:\cbx\mars\mars.d(1086)
0x005FF73B in D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ6runAllMFZ9__lambda1MFNlZv
0x005FF6FF in scope void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runAll()
0x005FF600 in _d_run_main
0x004DCDD8 in main at C:\cbx\mars\root\stringtable.d(7)
0x0061B245 in mainCRTStartup
0x74F3336A in BaseThreadInitThunk
0x77359902 in RtlInitializeExceptionChain
0x773598D5 in RtlInitializeExceptionChain
It appears to be a forward reference error. The code itself cannot work because RefCounted stores an instance of S in itself, and a struct cannot have itself as a field. In fact, the same error occurs with the following example:
struct RefCounted {
S s;
}
struct S {
int x;
RefCounted s;
}
Looks like my copy of dmd is out of date. HEAD is passing the example. Closing because it works now.
Comment #6 by ag0aep6g — 2017-10-08T08:55:49Z
(In reply to Walter Bright from comment #5)
> Looks like my copy of dmd is out of date. HEAD is passing the example.
> Closing because it works now.
I can't confirm that. DMD64 D Compiler v2.076.1-b1-169-g5db88ac83 gives me "Error: struct test.S no size because of forward reference". Reopening.
Comment #7 by bugzilla — 2019-12-17T10:25:54Z
With master, this now produces:
std/traits.d(2713): Error: unable to determine fields of S because of forward references
std/traits.d(3353): Error: template instance std.traits.FieldTypeTuple!(S) error instantiating
std/typecons.d(6243): instantiated from here: hasIndirections!(S)
test.d(6): instantiated from here: RefCounted!(S, cast(RefCountedAutoInitialize)1)
Comment #8 by robert.schadek — 2024-12-13T18:47:41Z