Nim Version

Nim Compiler Version 2.2.2 [Linux: amd64]
Compiled at 2025-02-06
Copyright (c) 2006-2025 by Andreas Rumpf

git hash: 6c34f62785263ad412f662f3e4e4bf8d8751d113
active boot switches: -d:release

Description

The following code is throwing a null pointer exception

!nim c --gc:arc

type
  Callback*[C] = proc(value: sink C): uint
  Person = object

proc invoke[C](target: Callback[C], values: sink C): uint =
  return target(values)

proc operation(value: sink (Person, string, int)): uint =
  return 123

doAssert invoke(operation, (Person(), "Jack", 25)) == 123

Current Output

Traceback (most recent call last)
/usercode/in.nim(11)     in
/usercode/in.nim(8)      invoke
SIGSEGV: Illegal storage access. (Attempt to read from nil?)
Segmentation fault (core dumped)

Expected Output

I expect that code to execute without a SIGSEGV

Known Workarounds

A few different changes will cause this code to work:

• Removing the sink param
• Removing any of the tuple parameters
• Calling the function directly instead of going through the invoke proc

Additional Information

It looks like the error is happening from within the destructor for the tuple, but I might be wrong about that.