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Issue 21693 - Lower scoped destruction of extern(C++) class to destroy/dtor call #12265
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e28736c
Issue 21693 - Lower scoped destruction of extern(C++) class to destroy
MoonlightSentinel 57858e4
Mimic struct destruction for stack allocated classes
MoonlightSentinel aa2147b
fixup! Issue 21693 - Lower scoped destruction of extern(C++) class to…
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,143 @@ | ||
| /* | ||
| https://issues.dlang.org/show_bug.cgi?id=21693 | ||
|
|
||
| RUN_OUTPUT: | ||
| --- | ||
| CppA: | ||
| 1: CppA.~this | ||
| CppB: | ||
| 2: CppB.~this | ||
| 2: CppA.~this | ||
| CppC: | ||
| 3: CppC.~this | ||
| 3: CppB.~this | ||
| 3: CppA.~this | ||
| CppC: | ||
| 4: CppC.~this | ||
| 4: CppB.~this | ||
| 4: CppA.~this | ||
| CppNoDestruct: | ||
| DA: | ||
| 1: DA.~this | ||
| DB: | ||
| 2: DB.~this | ||
| 2: DA.~this | ||
| DC: | ||
| 3: DC.~this | ||
| 3: DB.~this | ||
| 3: DA.~this | ||
| DC: | ||
| 4: DC.~this | ||
| 4: DB.~this | ||
| 4: DA.~this | ||
| --- | ||
| */ | ||
|
|
||
| extern (C) int printf(scope const char*, ...); | ||
|
|
||
| extern (C++) class CppA | ||
| { | ||
| int num; | ||
| this(int num) | ||
| { | ||
| this.num = num; | ||
| } | ||
|
|
||
| ~this() | ||
| { | ||
| printf("%d: CppA.~this\n", num); | ||
| } | ||
| } | ||
|
|
||
| extern (C++) class CppB : CppA | ||
| { | ||
| this(int num) | ||
| { | ||
| super(num); | ||
| } | ||
|
|
||
| ~this() | ||
| { | ||
| printf("%d: CppB.~this\n", num); | ||
| } | ||
| } | ||
|
|
||
| extern (C++) class CppC : CppB | ||
| { | ||
| this(int num) | ||
| { | ||
| super(num); | ||
| } | ||
|
|
||
| ~this() | ||
| { | ||
| printf("%d: CppC.~this\n", num); | ||
| } | ||
| } | ||
|
|
||
| extern (D) class DA | ||
| { | ||
| int num; | ||
| this(int num) | ||
| { | ||
| this.num = num; | ||
| } | ||
|
|
||
| ~this() | ||
| { | ||
| printf("%d: DA.~this\n", num); | ||
| } | ||
| } | ||
|
|
||
| extern (D) class DB : DA | ||
| { | ||
| this(int num) | ||
| { | ||
| super(num); | ||
| } | ||
|
|
||
| ~this() | ||
| { | ||
| printf("%d: DB.~this\n", num); | ||
| } | ||
| } | ||
|
|
||
| extern (D) class DC : DB | ||
| { | ||
| this(int num) | ||
| { | ||
| super(num); | ||
| } | ||
|
|
||
| ~this() | ||
| { | ||
| printf("%d: DC.~this\n", num); | ||
| } | ||
| } | ||
|
|
||
| extern (C++) class CppNoDestruct | ||
| { | ||
| int num; | ||
| this(int num) | ||
| { | ||
| this.num = num; | ||
| } | ||
| } | ||
|
|
||
| void main() | ||
| { | ||
| printf("CppA:\n"); { scope a = new CppA(1); } | ||
| printf("CppB:\n"); { scope CppA b = new CppB(2); } | ||
| printf("CppC:\n"); { scope CppA c = new CppC(3); } | ||
| printf("CppC:\n"); { scope CppB c2 = new CppC(4); } | ||
|
|
||
| printf("CppNoDestruct:\n"); | ||
| { | ||
| scope const nd = new CppNoDestruct(1); | ||
| } | ||
|
|
||
| printf("DA:\n"); { scope a = new DA(1); } | ||
| printf("DB:\n"); { scope DA b = new DB(2); } | ||
| printf("DC:\n"); { scope DA c = new DC(3); } | ||
| printf("DC:\n"); { scope DB c2 = new DC(4); } | ||
| } |
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destroyshould be used instead ofdeletefor for D classes, too: https://issues.dlang.org/show_bug.cgi?id=21692There was a problem hiding this comment.
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destroydoesn't work forconst/immutableeither (unless we insert an explicit cast to mutable)There was a problem hiding this comment.
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Implemented another approach, it's now directly calling the dtor (effectively inlining the call to
destroy).This matches the implementation for
structs and allows the hack to call dtors on immutable instances.There was a problem hiding this comment.
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Seems like it does (tested with v2.096.0). Anyway, the direct dtor call is better. Is there a reason you don't use it for D classes too? I find it inconsistent (can use
scope const/immutablewith C++ classes, but not with D ones) and don't really like deprecated expressions in compiler-generated AST nodes. ;)There was a problem hiding this comment.
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Nevermind, seems like it was an issue with the lowering.
Mostly because
destroy(anddeleteIIRC) refer tort_finalize2which does more cleanup than just calling the dtor. Not sure if those additional steps are required for stack allocated instances...But lowering to
destroywould still work for D classes.There was a problem hiding this comment.
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Yeah that'd be great.
You're right, for D classes, there's apparently the need to descend to all base classes and invoke the dtors manually (via TypeInfo... argh), and the monitor might need cleanup too. LDC has a special case for these
deleteexpressions forscopeclasses and tries to avoid calling druntime if the class has no finalizer and the monitor is null: https://github.com/ldc-developers/ldc/blob/937c57b8354d4821daededb35abdb77d16ce3737/gen/classes.cpp#L200-L222Doing this here in the frontend directly would obviously be much nicer.
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Maybe the best way forward is to replace the
TypeInfobased dtor-loop in DRuntime with a real dtor chain as done for C++ classes and to move the cleanup into `Object.~this()). That would cause less (magic) code scattered across dmd/druntime/ldc/... .Anyway, lowering to
destroydoesn't work yet.@nogcdestroy(it needs some special casing as done fordelete)