ORC: use =destroy instead of =dispose (#18440)

* ORC refactoring in preparation for further changes (=dispose must die)
* ORC: embrace =destroy, avoid =dispose
* ORC: no need for =dispose
* closes #18421

4 files changed, 37 insertions, 33 deletions

diff --git a/lib/system.nim b/lib/system.nim
index a4608997a..090ab309e 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -1779,7 +1779,6 @@ when not defined(js) and defined(nimV2):
       align: int
       name: cstring
       traceImpl: pointer
-      disposeImpl: pointer
       typeInfoV1: pointer # for backwards compat, usually nil
       flags: int
     PNimTypeV2 = ptr TNimTypeV2
diff --git a/lib/system/cellseqs_v2.nim b/lib/system/cellseqs_v2.nim
index 59cf67dcd..27be48d78 100644
--- a/lib/system/cellseqs_v2.nim
+++ b/lib/system/cellseqs_v2.nim
@@ -10,20 +10,20 @@
 # Cell seqs for cyclebreaker and cyclicrefs_v2.
 
 type
-  CellTuple = (PT, PNimTypeV2)
-  CellArray = ptr UncheckedArray[CellTuple]
-  CellSeq = object
+  CellTuple[T] = (T, PNimTypeV2)
+  CellArray[T] = ptr UncheckedArray[CellTuple[T]]
+  CellSeq[T] = object
     len, cap: int
-    d: CellArray
+    d: CellArray[T]
 
-proc add(s: var CellSeq, c: PT; t: PNimTypeV2) {.inline.} =
+proc add[T](s: var CellSeq[T], c: T; t: PNimTypeV2) {.inline.} =
   if s.len >= s.cap:
     s.cap = s.cap * 3 div 2
     when compileOption("threads"):
-      var d = cast[CellArray](allocShared(uint(s.cap * sizeof(CellTuple))))
+      var d = cast[CellArray[T]](allocShared(uint(s.cap * sizeof(CellTuple[T]))))
     else:
-      var d = cast[CellArray](alloc(s.cap * sizeof(CellTuple)))
-    copyMem(d, s.d, s.len * sizeof(CellTuple))
+      var d = cast[CellArray[T]](alloc(s.cap * sizeof(CellTuple[T])))
+    copyMem(d, s.d, s.len * sizeof(CellTuple[T]))
     when compileOption("threads"):
       deallocShared(s.d)
     else:
@@ -33,15 +33,15 @@ proc add(s: var CellSeq, c: PT; t: PNimTypeV2) {.inline.} =
   s.d[s.len] = (c, t)
   inc(s.len)
 
-proc init(s: var CellSeq, cap: int = 1024) =
+proc init[T](s: var CellSeq[T], cap: int = 1024) =
   s.len = 0
   s.cap = cap
   when compileOption("threads"):
-    s.d = cast[CellArray](allocShared(uint(s.cap * sizeof(CellTuple))))
+    s.d = cast[CellArray[T]](allocShared(uint(s.cap * sizeof(CellTuple[T]))))
   else:
-    s.d = cast[CellArray](alloc(s.cap * sizeof(CellTuple)))
+    s.d = cast[CellArray[T]](alloc(s.cap * sizeof(CellTuple[T])))
 
-proc deinit(s: var CellSeq) =
+proc deinit[T](s: var CellSeq[T]) =
   if s.d != nil:
     when compileOption("threads"):
       deallocShared(s.d)
@@ -51,6 +51,6 @@ proc deinit(s: var CellSeq) =
   s.len = 0
   s.cap = 0
 
-proc pop(s: var CellSeq): (PT, PNimTypeV2) =
+proc pop[T](s: var CellSeq[T]): (T, PNimTypeV2) =
   result = s.d[s.len-1]
   dec s.len
diff --git a/lib/system/cyclebreaker.nim b/lib/system/cyclebreaker.nim
index a3159f95c..6ec0f01f7 100644
--- a/lib/system/cyclebreaker.nim
+++ b/lib/system/cyclebreaker.nim
@@ -53,7 +53,6 @@ depth-first traversal suffices.
 
 ]#
 
-type PT = ptr pointer
 include cellseqs_v2
 
 const
@@ -78,7 +77,7 @@ proc nimMarkCyclic(p: pointer) {.compilerRtl, inl.} = discard
 
 type
   GcEnv = object
-    traceStack: CellSeq
+    traceStack: CellSeq[ptr pointer]
 
 proc trace(p: pointer; desc: PNimTypeV2; j: var GcEnv) {.inline.} =
   when false:
diff --git a/lib/system/orc.nim b/lib/system/orc.nim
index df81afcf1..6273e1a21 100644
--- a/lib/system/orc.nim
+++ b/lib/system/orc.nim
@@ -14,7 +14,6 @@
 # R.D. Lins / Information Processing Letters 109 (2008) 71–78
 #
 
-type PT = Cell
 include cellseqs_v2
 
 const
@@ -68,10 +67,10 @@ const
 
 type
   GcEnv = object
-    traceStack: CellSeq
+    traceStack: CellSeq[ptr pointer]
     when useJumpStack:
-      jumpStack: CellSeq   # Lins' jump stack in order to speed up traversals
-    toFree: CellSeq
+      jumpStack: CellSeq[ptr pointer]   # Lins' jump stack in order to speed up traversals
+    toFree: CellSeq[Cell]
     freed, touched, edges, rcSum: int
     keepThreshold: bool
 
@@ -92,13 +91,13 @@ proc free(s: Cell; desc: PNimTypeV2) {.inline.} =
 
   when logOrc: writeCell("free", s, desc)
 
-  if desc.disposeImpl != nil:
-    cast[DisposeProc](desc.disposeImpl)(p)
+  if desc.destructor != nil:
+    cast[DestructorProc](desc.destructor)(p)
 
   when false:
     cstderr.rawWrite desc.name
     cstderr.rawWrite " "
-    if desc.disposeImpl == nil:
+    if desc.destructor == nil:
       cstderr.rawWrite "lacks dispose"
       if desc.traceImpl != nil:
         cstderr.rawWrite ", but has trace\n"
@@ -125,16 +124,16 @@ proc nimTraceRef(q: pointer; desc: PNimTypeV2; env: pointer) {.compilerRtl, inli
     orcAssert strstr(desc.name, "TType") == nil, "following a TType but it's acyclic!"
 
     var j = cast[ptr GcEnv](env)
-    j.traceStack.add(head p[], desc)
+    j.traceStack.add(p, desc)
 
 proc nimTraceRefDyn(q: pointer; env: pointer) {.compilerRtl, inline.} =
   let p = cast[ptr pointer](q)
   if p[] != nil:
     var j = cast[ptr GcEnv](env)
-    j.traceStack.add(head p[], cast[ptr PNimTypeV2](p[])[])
+    j.traceStack.add(p, cast[ptr PNimTypeV2](p[])[])
 
 var
-  roots {.threadvar.}: CellSeq
+  roots {.threadvar.}: CellSeq[Cell]
 
 proc unregisterCycle(s: Cell) =
   # swap with the last element. O(1)
@@ -162,7 +161,8 @@ proc scanBlack(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
   trace(s, desc, j)
   when logOrc: writeCell("root still alive", s, desc)
   while j.traceStack.len > until:
-    let (t, desc) = j.traceStack.pop()
+    let (entry, desc) = j.traceStack.pop()
+    let t = head entry[]
     inc t.rc, rcIncrement
     if t.color != colBlack:
       t.setColor colBlack
@@ -187,7 +187,8 @@ proc markGray(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
     orcAssert(j.traceStack.len == 0, "markGray: trace stack not empty")
     trace(s, desc, j)
     while j.traceStack.len > 0:
-      let (t, desc) = j.traceStack.pop()
+      let (entry, desc) = j.traceStack.pop()
+      let t = head entry[]
       dec t.rc, rcIncrement
       inc j.edges
       when useJumpStack:
@@ -195,7 +196,7 @@ proc markGray(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
           t.rc = t.rc or jumpStackFlag
           when traceCollector:
             cprintf("[Now in jumpstack] %p %ld color %ld in jumpstack %ld\n", t, t.rc shr rcShift, t.color, t.rc and jumpStackFlag)
-          j.jumpStack.add(t, desc)
+          j.jumpStack.add(entry, desc)
       if t.color != colGray:
         t.setColor colGray
         inc j.touched
@@ -225,7 +226,8 @@ proc scan(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
         # that are still alive; we also need to mark what they
         # refer to as alive:
         while j.jumpStack.len > 0:
-          let (t, desc) = j.jumpStack.pop
+          let (entry, desc) = j.jumpStack.pop
+          let t = head entry[]
           # not in jump stack anymore!
           t.rc = t.rc and not jumpStackFlag
           if t.color == colGray and (t.rc shr rcShift) >= 0:
@@ -239,7 +241,8 @@ proc scan(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
       s.setColor(colWhite)
       trace(s, desc, j)
       while j.traceStack.len > 0:
-        let (t, desc) = j.traceStack.pop()
+        let (entry, desc) = j.traceStack.pop()
+        let t = head entry[]
         if t.color == colGray:
           if (t.rc shr rcShift) >= 0:
             scanBlack(t, desc, j)
@@ -249,7 +252,8 @@ proc scan(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
               # that are still alive; we also need to mark what they
               # refer to as alive:
               while j.jumpStack.len > 0:
-                let (t, desc) = j.jumpStack.pop
+                let (entry, desc) = j.jumpStack.pop
+                let t = head entry[]
                 # not in jump stack anymore!
                 t.rc = t.rc and not jumpStackFlag
                 if t.color == colGray and (t.rc shr rcShift) >= 0:
@@ -285,7 +289,9 @@ proc collectColor(s: Cell; desc: PNimTypeV2; col: int; j: var GcEnv) =
     j.toFree.add(s, desc)
     trace(s, desc, j)
     while j.traceStack.len > 0:
-      let (t, desc) = j.traceStack.pop()
+      let (entry, desc) = j.traceStack.pop()
+      let t = head entry[]
+      entry[] = nil # ensure that the destructor does touch moribund objects!
       if t.color == col and t.rootIdx == 0:
         j.toFree.add(t, desc)
         t.setColor(colBlack)