Nim check hangs in macro

[liwt31]

Nim check hangs in macro. Don't know what exactly caused this.

Example

Content of bug.nim:

macro foo(): untyped  = 
  let lines = ["123", "5423"]
  var idx = 0
  while idx < lines.len():
    if lines[idx].len() < 1: 
      inc(idx)
      continue
 
foo()

Current Output

$ nim check bug.nim 
Hint: used config file '/home/wtli/.choosenim/toolchains/nim-0.19.0/config/nim.cfg' [Conf]
Hint: system [Processing]
Hint: bug [Processing]
^CSIGINT: Interrupted by Ctrl-C.
Traceback (most recent call last)
proxyexe.nim(62)         proxyexe
proxyexe.nim(49)         main
osproc.nim(1136)         waitForExit
SIGINT: Interrupted by Ctrl-C.

The program hangs in Hint: bug [Processing] until a SIGINT.

Expected Output

I know there's a infinite loop, but I've seen:

Error: interpretation requires too many iterations; if you are sure this is not a bug in your code edit compiler/vmdef.MaxLoopIterations and rebuild the compiler

before in a simpler case. That's a lot nicer (and very cool!).

Possible Solution

Donno.

Additional Information

Nim Compiler Version 0.19.0 [Linux: amd64]
Compiled at 2018-09-26
Copyright (c) 2006-2018 by Andreas Rumpf

git hash: f6c5c636bb1a1f4e1301ae0ba5a8afecef439132
active boot switches: -d:release

Linux localhost.localdomain 3.10.0-862.el7.x86_64 #1 SMP Fri Apr 20 16:44:24 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Thank you in advance.

[nc-x]

@Araq Why the crash label, this is not a crash.

@liwt31

Don't know what exactly caused this.

macro foo(): untyped  = 
  let lines = ["123", "5423"]
  var idx = 0
  while idx < lines.len():                   -----
    if lines[idx].len() < 1:                      | Infinite loop because inc(idx) is never called
      inc(idx)                                    | 
      continue                               -----
 
foo()

A macro is evaluated at compile time. And you created an infinite loop (which runs at compile time). So the compilation nevers completes.

Also the issue is not specific to nim check. nim c also gets stuck at infinite loop.

[Araq]

The VM doesn't have infinite loops, an infinite loop is a crash.