ported to FreeRTOS

(cherry picked from commit 9f56688)

lib/pure/asyncdispatch.nim

@@ -1946,13 +1946,15 @@ proc activeDescriptors*(): int {.inline.} =
 when defined(posix):
   import posix
 
-proc maxDescriptors*(): int {.raises: OSError.} =
-  ## Returns the maximum number of active file descriptors for the current
-  ## process. This involves a system call.
-  when defined(windows):
-    result = 16_700_000
-  else:
-    var fdLim: RLimit
-    if getrlimit(RLIMIT_NOFILE, fdLim) < 0:
-      raiseOSError(osLastError())
-    result = int(fdLim.rlim_cur) - 1
+when defined(linux) or defined(windows) or defined(macosx) or defined(bsd):
+  proc maxDescriptors*(): int {.raises: OSError.} =
+    ## Returns the maximum number of active file descriptors for the current
+    ## process. This involves a system call. For now `maxDescriptors` is
+    ## supported on the following OSes: Windows, Linux, OSX, BSD.
+    when defined(windows):
+      result = 16_700_000
+    else:
+      var fdLim: RLimit
+      if getrlimit(RLIMIT_NOFILE, fdLim) < 0:
+        raiseOSError(osLastError())
+      result = int(fdLim.rlim_cur) - 1

lib/pure/asynchttpserver.nim

@@ -308,9 +308,18 @@ proc processClient(server: AsyncHttpServer, client: AsyncSocket, address: string
     )
     if not retry: break
 
+const
+  nimMaxDescriptorsFallback* {.intdefine.} = 16_000 ## fallback value for \
+    ## when `maxDescriptors` is not available.
+    ## This can be set on the command line during compilation
+    ## via `-d:nimMaxDescriptorsFallback=N`
+
 proc listen*(server: AsyncHttpServer; port: Port; address = "") =
   ## Listen to the given port and address.
-  server.maxFDs = maxDescriptors()
+  when declared(maxDescriptors):
+    server.maxFDs = try: maxDescriptors() except: nimMaxDescriptorsFallback
+  else:
+    server.maxFDs = nimMaxDescriptorsFallback
   server.socket = newAsyncSocket()
   if server.reuseAddr:
     server.socket.setSockOpt(OptReuseAddr, true)