From 6c9730b3534927ac2bdd4ec7c77e0d37bba7aa2e Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Sat, 11 Oct 2014 12:25:15 +0200
Subject: [PATCH] fixes #1551

---
 compiler/semexprs.nim               | 5 +++++
 lib/pure/concurrency/threadpool.nim | 6 +++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index ff445ecd09..46e6f1ab3c 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -1614,6 +1614,11 @@ proc instantiateCreateFlowVarCall(c: PContext; t: PType;
   initIdTable(bindings)
   bindings.idTablePut(sym.ast[genericParamsPos].sons[0].typ, t)
   result = c.semGenerateInstance(c, sym, bindings, info)
+  # since it's an instantiation, we unmark it as a compilerproc. Otherwise
+  # codegen would fail:
+  if sfCompilerProc in result.flags:
+    result.flags = result.flags - {sfCompilerProc, sfExportC, sfImportC}
+    result.loc.r = nil
 
 proc setMs(n: PNode, s: PSym): PNode = 
   result = n
diff --git a/lib/pure/concurrency/threadpool.nim b/lib/pure/concurrency/threadpool.nim
index e0a2ac6782..f46822d941 100644
--- a/lib/pure/concurrency/threadpool.nim
+++ b/lib/pure/concurrency/threadpool.nim
@@ -95,7 +95,7 @@ type
 
   FlowVarBase* = ref FlowVarBaseObj ## untyped base class for 'FlowVar[T]'
   FlowVarBaseObj = object of TObject
-    ready, usesCondVar: bool
+    ready, usesCondVar, awaited: bool
     cv: CondVar #\
     # for 'awaitAny' support
     ai: ptr AwaitInfo
@@ -129,8 +129,8 @@ type
 proc await*(fv: FlowVarBase) =
   ## waits until the value for the flowVar arrives. Usually it is not necessary
   ## to call this explicitly.
-  if fv.usesCondVar:
-    fv.usesCondVar = false
+  if fv.usesCondVar and not fv.awaited:
+    fv.awaited = true
     await(fv.cv)
     destroyCondVar(fv.cv)