fixes #24402; Memory leak under Arc/Orc on inline iterators with nested seq

Author: ringabout

compiler/transf.nim

@@ -400,7 +400,8 @@ proc transformYield(c: PTransf, n: PNode): PNode =
           let lhs = c.transCon.forStmt[i]
           let rhs = transform(c, v)
           result.add(asgnTo(lhs, rhs))
-    elif e.kind notin {nkAddr, nkHiddenAddr}: # no need to generate temp for address operation
+    elif e.kind notin {nkAddr, nkHiddenAddr} and e.kind != nkSym:
+      # no need to generate temp for address operation + nodes without sideeffects
       # TODO do not use temp for nodes which cannot have side-effects
       var tmp = newTemp(c, e.typ, e.info)
       let v = newNodeI(nkVarSection, e.info)
@@ -435,7 +436,8 @@ proc transformYield(c: PTransf, n: PNode): PNode =
       else:
         notLiteralTuple = true
 
-      if e.kind notin {nkAddr, nkHiddenAddr} and notLiteralTuple:
+      if e.kind notin {nkAddr, nkHiddenAddr} and notLiteralTuple and e.kind != nkSym:
+        # no need to generate temp for address operation + nodes without sideeffects
         # TODO do not use temp for nodes which cannot have side-effects
         var tmp = newTemp(c, e.typ, e.info)
         let v = newNodeI(nkVarSection, e.info)

tests/arc/t24402.nim

@@ -0,0 +1,54 @@
+discard """
+  joinable: false
+"""
+
+# bug #24402
+
+iterator myPairsInline*[T](twoDarray: seq[seq[T]]): (int, seq[T]) {.inline.} =
+  for indexValuePair in twoDarray.pairs:
+    yield indexValuePair
+
+iterator myPairsClosure*[T](twoDarray: seq[seq[T]]): (int, seq[T]) {.closure.} =
+  for indexValuePair in twoDarray.pairs:
+    yield indexValuePair
+
+template testTotalMem(iter: untyped): int =
+  proc innerTestTotalMem(): int {.gensym.} =
+    result = 0
+
+    # do the same operation 100 times, which should have similar mem footprint
+    # as doing it once.
+    for iterNum in 0..100:
+      result = max(result, getTotalMem()) # record current mem footprint
+
+      # initialize nested sequence
+      var my2dArray: seq[seq[int32]] = @[]
+
+      # fill with some data...
+      for i in 0'i32..10_000:
+        var z = @[i, i+1]
+        my2dArray.add z
+
+      # use that data somehow...
+      var otherContainer: seq[int32] = @[]
+      var count = 0'i32
+      for oneDindex, innerArray in my2dArray.iter:
+        for value in innerArray:
+          inc count
+          if oneDindex > 50 and value < 200:
+            otherContainer.add count
+
+  innerTestTotalMem()
+
+proc main =
+  let closureMem = testTotalMem(myPairsClosure) #1052672
+  let inlineMem = testTotalMem(myPairsInline) #20328448
+
+  when defined(echoFootprint):
+    echo "Closure memory footprint: " & $closureMem
+    echo "Inline memory footprint: " & $inlineMem
+
+  # check that mem footprint is relatively similar b/t each method
+  doAssert (closureMem - inlineMem).abs < (closureMem div 10)
+
+main()