Object destructor not called when reassigning after a try-except block.

nim-lang / Nim

Nim is a statically typed compiled systems programming language. It combines successful concepts from mature languages like Python, Ada and Modula. Its design focuses on efficiency, expressiveness, and elegance (in that order of priority).

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Description

Object destructor not called when reassigning after a try-except block.

Minimal example:

import std/os

type MyObj = object
  data: pointer
  size: int

proc initMyObj(size: int): MyObj =
  assert size > 0
  result.data = allocShared0(size)
  result.size = size

  # imitate work
  let p = cast[ptr UncheckedArray[uint8]](result.data)
  for i in 0..<size:
    p[i] = i.uint8

proc `=destroy`(x: MyObj) =
  if not x.data.isNil:
    deallocShared(x.data)

proc `=wasMoved`(x: var MyObj) =
  x.data = nil
  x.size = 0

proc `=copy`(x: var MyObj, y: MyObj) {.error.}

proc main() =
  while true:
    var obj: MyObj
    try:
      obj = initMyObj(10_000_000)
    except:
    # except FloatOverflowError: also causes a leak, although it is never raised
      break

    # discard obj

    obj = MyObj()
    sleep(20)

    echo getOccupiedMem()

main()

Uncommenting the discard obj line removes the issue.

Nim Version

Both on

Nim Compiler Version 2.0.8 [Linux: amd64]
Compiled at 2024-07-03
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: 5935c3bfa9fec6505394867b23510eb5cbab3dbf
active boot switches: -d:release

and

Nim Compiler Version 2.1.99 [Linux: amd64]
Compiled at 2024-09-12
Copyright (c) 2006-2024 by Andreas Rumpf

git hash: 793cee4de1934fd1f6271cf5fed46f01c5abb19b
active boot switches: -d:release

Current Output

Expected Output

Known Workarounds

In the example above, uncommenting the discard obj line removes the issue.

Additional Information

No response

The test source

import std/os type MyObj = object data: pointer size: int proc initMyObj(size: int): MyObj = assert size > 0 result.data = allocShared0(size) result.size = size # imitate work let p = cast[ptr UncheckedArray[uint8]](result.data) for i in 0..<size: p[i] = i.uint8 proc `=destroy`(x: MyObj) = if not x.data.isNil: deallocShared(x.data) proc `=wasMoved`(x: var MyObj) = x.data = nil x.size = 0 proc `=copy`(x: var MyObj, y: MyObj) {.error.} proc main() = while true: var obj: MyObj discard obj try: obj = initMyObj(10_000_000) except: # except FloatOverflowError: also causes a leak, although it is never raised break # discard obj obj = MyObj() sleep(20) echo getOccupiedMem() main()

Test test source

import std/os type MyObj = object data: pointer size: int proc initMyObj(size: int): MyObj = assert size > 0 result.data = allocShared0(size) result.size = size # imitate work let p = cast[ptr UncheckedArray[uint8]](result.data) for i in 0..<size: p[i] = i.uint8 proc `=destroy`(x: var MyObj) = # Using `var` in nim-1.6.20 if not x.data.isNil: deallocShared(x.data) proc `=wasMoved`(x: var MyObj) = x.data = nil x.size = 0 proc `=copy`(x: var MyObj, y: MyObj) {.error.} proc main() = while true: var obj: MyObj try: obj = initMyObj(10_000_000) except: # except FloatOverflowError: also causes a leak, although it is never raised break # discard obj obj = MyObj() sleep(20) echo getOccupiedMem() main()

nim-lang / Nim