Nim Hot Code Reloading tests fail on OpenBSD

[euantorano]

There are several nimhcr tests that fail on OpenBSD with a Not supported [OSError] error. THe problem appears to be in the reservedmem module as they all fail with a stacktrace similar to the following:

Category: dll
Name: tests/dll/nimhcr_unit.nim C
Action: run
Result: reExitcodesDiffer
-------- Expected -------
exitcode: 0
--------- Given  --------
exitcode: 1

Output:
nimhcr_unit.nim(107)     nimhcr_unit
/home/administrator/build/Nim/lib/nimhcr.nim(342) hcrRegisterProc
/home/administrator/build/Nim/lib/pure/reservedmem.nim(217) setLen
/home/administrator/build/Nim/lib/pure/reservedmem.nim(94) setLen
/home/administrator/build/Nim/lib/pure/includes/oserr.nim(94) raiseOSError
Error: unhandled exception: Not supported [OSError]

[timotheecour]

The stacktrace isn't super helpful because check is a template, not a proc, so it can't (currently! refs timotheecour#447) tell which line it was called from:

  template check(expr) =
    if not expr:
      raiseOSError(osLastError())

but as I saw in #16329 it actually points to one of these failing:
check mprotect or check posix_madvise

proc setLen*(m: var ReservedMem, newLen: int) =
  let len = m.len
  m.usedMemEnd = m.memStart.shift(newLen)
  if newLen > len:
    let d = distance(m.committedMemEnd, m.usedMemEnd)
    if d > 0:
      let commitExtensionSize = nextAlignedOffset(d, allocationGranularity)
      when defined(windows):
        check virtualAlloc(m.committedMemEnd, commitExtensionSize,
                           MEM_COMMIT, m.accessFlags.cint)
      else:
        check mprotect(m.committedMemEnd, commitExtensionSize,
            m.accessFlags.cint) == 0
  else:
    let d = distance(m.usedMemEnd, m.committedMemEnd) -
            m.maxCommittedAndUnusedPages * allocationGranularity
    if d > 0:
      let commitSizeShrinkage = nextAlignedOffset(d, allocationGranularity)
      let newCommitEnd = m.committedMemEnd.shift(-commitSizeShrinkage)

      when defined(windows):
        check virtualFree(newCommitEnd, commitSizeShrinkage, MEM_DECOMMIT)
      else:
        check posix_madvise(newCommitEnd, commitSizeShrinkage,
                            POSIX_MADV_DONTNEED) == 0

      m.committedMemEnd = newCommitEnd

upon further investigation i found this comment:

OpenBSD however doesn't implement posix_madvise().

in https://patchwork.ozlabs.org/project/qemu-devel/patch/1284224755-11299-1-git-send-email-andreas.faerber@web.de/

but there's some contradiction with other sources I found on the topic; it my depend on glibc etc

links

• http://man.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/madvise.2
• https://github.com/dlang/druntime/blob/master/src/core/sys/openbsd/sys/mman.d no mention of posix_madvise, only madvise

EDIT

looks like it's in fact check mprotect the culprit (really hard to debug via CI)

        check mprotect(m.committedMemEnd, commitExtensionSize,
            m.accessFlags.cint) == 0

I can't find any relevant reference on the web / nim sources to "Not supported" from the errmsg
Error: unhandled exception: Not supported [OSError] so it's not clear where that comes from.

Further investigation needs to look what was this equal to: m.accessFlags.cint