Fixes crashes when asyncdispatch.adjustTimeout returns a negative value. (#11231)

lib/pure/asyncdispatch.nim

@@ -211,11 +211,10 @@ proc processPendingCallbacks(p: PDispatcherBase; didSomeWork: var bool) =
     didSomeWork = true
 
 proc adjustTimeout(pollTimeout: int, nextTimer: Option[int]): int {.inline.} =
-  if nextTimer.isNone():
+  if nextTimer.isNone() or pollTimeout == -1:
     return pollTimeout
 
-  result = nextTimer.get()
+  result = max(nextTimer.get(), 0)
-  if pollTimeout == -1: return
   result = min(pollTimeout, result)
 
 proc callSoon*(cbproc: proc () {.gcsafe.}) {.gcsafe.}

lib/pure/ioselects/ioselectors_epoll.nim

@@ -378,6 +378,8 @@ proc selectInto*[T](s: Selector[T], timeout: int,
   if maxres > len(results):
     maxres = len(results)
 
+  verifySelectParams(timeout)
+
   let count = epoll_wait(s.epollFD, addr(resTable[0]), maxres.cint,
                          timeout.cint)
   if count < 0:

lib/pure/ioselects/ioselectors_kqueue.nim

@@ -44,8 +44,8 @@ elif defined(netbsd) or defined(openbsd):
 when hasThreadSupport:
   type
     SelectorImpl[T] = object
-      kqFD : cint
+      kqFD: cint
-      maxFD : int
+      maxFD: int
       changes: ptr SharedArray[KEvent]
       fds: ptr SharedArray[SelectorKey[T]]
       count: int
@@ -57,8 +57,8 @@ when hasThreadSupport:
 else:
   type
     SelectorImpl[T] = object
-      kqFD : cint
+      kqFD: cint
-      maxFD : int
+      maxFD: int
       changes: seq[KEvent]
       fds: seq[SelectorKey[T]]
       count: int
@@ -447,6 +447,8 @@ proc selectInto*[T](s: Selector[T], timeout: int,
     ptv = addr tv
     maxres = MAX_KQUEUE_EVENTS
 
+  verifySelectParams(timeout)
+
   if timeout != -1:
     if timeout >= 1000:
       tv.tv_sec = posix.Time(timeout div 1_000)

lib/pure/ioselects/ioselectors_poll.nim

@@ -214,6 +214,8 @@ proc selectInto*[T](s: Selector[T], timeout: int,
   if maxres > len(results):
     maxres = len(results)
 
+  verifySelectParams(timeout)
+
   s.withPollLock():
     let count = posix.poll(addr(s.pollfds[0]), Tnfds(s.pollcnt), timeout)
     if count < 0:

lib/pure/ioselects/ioselectors_select.nim

@@ -309,6 +309,8 @@ proc selectInto*[T](s: Selector[T], timeout: int,
   var ptv = addr tv
   var rset, wset, eset: FdSet
 
+  verifySelectParams(timeout)
+
   if timeout != -1:
     when defined(genode):
       tv.tv_sec = Time(timeout div 1_000)

lib/pure/selectors.nim

@@ -314,6 +314,14 @@ else:
     key.events = {}
     key.data = empty
 
+  proc verifySelectParams(timeout: int) =
+    # Timeout of -1 means: wait forever
+    # Anything higher is the time to wait in miliseconds.
+    if timeout < -1:
+      raise newException(
+        ValueError, "Cannot select with a negative value, got " & $timeout
+      )
+
   when defined(linux):
     include ioselects/ioselectors_epoll
   elif bsdPlatform: