From 9b9cd452affa2b0f632435b975ab8851589a8ba4 Mon Sep 17 00:00:00 2001
From: Mauro Werder <mauro3@runbox.com>
Date: Wed, 27 Nov 2019 15:26:53 +0100
Subject: [PATCH] Make the at-threads a no-op if nthreads()==0

---
 base/threadingconstructs.jl | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/base/threadingconstructs.jl b/base/threadingconstructs.jl
index 1d88c882a0688..baf8ab394e142 100644
--- a/base/threadingconstructs.jl
+++ b/base/threadingconstructs.jl
@@ -19,6 +19,8 @@ on `threadid()`.
 nthreads() = Int(unsafe_load(cglobal(:jl_n_threads, Cint)))
 
 function _threadsfor(iter,lbody)
+    nthreads()==1 && return esc(Expr(:for, iter, lbody)) # do nothing if there are not threads
+
     lidx = iter.args[1]         # index
     range = iter.args[2]
     quote