diff --git a/L/Libtask/build_dylib.sh b/L/Libtask/build_dylib.sh
deleted file mode 100644
index 3fd0089ddd0..00000000000
--- a/L/Libtask/build_dylib.sh
+++ /dev/null
@@ -1,62 +0,0 @@
-#!/bin/bash
-
-# target=x86_64-linux-gnu
-cd $WORKSPACE/srcdir
-
-RELEASES=(
-    arm-linux-gnueabihf@v1_0@https://julialang-s3.julialang.org/bin/linux/armv7l/1.0/julia-1.0.0-linux-armv7l.tar.gz
-    arm-linux-gnueabihf@v1_2@https://julialang-s3.julialang.org/bin/linux/armv7l/1.2/julia-1.2.0-linux-armv7l.tar.gz
-    arm-linux-gnueabihf@v1_3@https://julialang-s3.julialang.org/bin/linux/armv7l/1.3/julia-1.3.0-linux-armv7l.tar.gz
-    aarch64-linux-gnu@v1_0@https://julialang-s3.julialang.org/bin/linux/aarch64/1.0/julia-1.0.4-linux-aarch64.tar.gz
-    aarch64-linux-gnu@v1_1@https://julialang-s3.julialang.org/bin/linux/aarch64/1.1/julia-1.1.1-linux-aarch64.tar.gz
-    aarch64-linux-gnu@v1_2@https://julialang-s3.julialang.org/bin/linux/aarch64/1.2/julia-1.2.0-linux-aarch64.tar.gz
-    aarch64-linux-gnu@v1_3@https://julialang-s3.julialang.org/bin/linux/aarch64/1.3/julia-1.3.0-linux-aarch64.tar.gz
-    i686-linux-gnu@v1_0@https://julialang-s3.julialang.org/bin/linux/x86/1.0/julia-1.0.0-linux-i686.tar.gz
-    i686-linux-gnu@v1_1@https://julialang-s3.julialang.org/bin/linux/x86/1.1/julia-1.1.0-linux-i686.tar.gz
-    i686-linux-gnu@v1_2@https://julialang-s3.julialang.org/bin/linux/x86/1.2/julia-1.2.0-linux-i686.tar.gz
-    i686-linux-gnu@v1_3@https://julialang-s3.julialang.org/bin/linux/x86/1.3/julia-1.3.0-linux-i686.tar.gz
-    x86_64-linux-gnu@v1_0@https://julialang-s3.julialang.org/bin/linux/x64/1.0/julia-1.0.0-linux-x86_64.tar.gz
-    x86_64-linux-gnu@v1_1@https://julialang-s3.julialang.org/bin/linux/x64/1.1/julia-1.1.0-linux-x86_64.tar.gz
-    x86_64-linux-gnu@v1_2@https://julialang-s3.julialang.org/bin/linux/x64/1.2/julia-1.2.0-linux-x86_64.tar.gz
-    x86_64-linux-gnu@v1_3@https://julialang-s3.julialang.org/bin/linux/x64/1.3/julia-1.3.0-linux-x86_64.tar.gz
-    powerpc64le-linux-gnu@v1_0@http://cxan.kdr2.com/julia/releases/julia-1.0.0-linux-ppc64le.tar.gz
-    powerpc64le-linux-gnu@v1_1@http://cxan.kdr2.com/julia/releases/julia-1.1.0-linux-ppc64le.tar.gz
-    powerpc64le-linux-gnu@v1_2@http://cxan.kdr2.com/julia/releases/julia-1.2.0-linux-ppc64le.tar.gz
-    powerpc64le-linux-gnu@v1_3@http://cxan.kdr2.com/julia/releases/julia-1.3.0-linux-ppc64le.tar.gz
-    x86_64-w64-mingw32@v1_0@http://cxan.kdr2.com/julia/releases/julia-1.0.0-win64.tar.gz
-    x86_64-w64-mingw32@v1_1@http://cxan.kdr2.com/julia/releases/julia-1.1.0-win64.tar.gz
-    x86_64-w64-mingw32@v1_2@http://cxan.kdr2.com/julia/releases/julia-1.2.0-win64.tar.gz
-    x86_64-w64-mingw32@v1_3@http://cxan.kdr2.com/julia/releases/julia-1.3.0-win64.tar.gz
-    i686-w64-mingw32@v1_0@http://cxan.kdr2.com/julia/releases/julia-1.0.0-win32.tar.gz
-    i686-w64-mingw32@v1_1@http://cxan.kdr2.com/julia/releases/julia-1.1.0-win32.tar.gz
-    i686-w64-mingw32@v1_2@http://cxan.kdr2.com/julia/releases/julia-1.2.0-win32.tar.gz
-    i686-w64-mingw32@v1_3@http://cxan.kdr2.com/julia/releases/julia-1.3.0-win32.tar.gz
-    x86_64-apple-darwin14@v1_0@http://cxan.kdr2.com/julia/releases/julia-1.0.0-mac64.tar.gz
-    x86_64-apple-darwin14@v1_1@http://cxan.kdr2.com/julia/releases/julia-1.1.0-mac64.tar.gz
-    x86_64-apple-darwin14@v1_2@http://cxan.kdr2.com/julia/releases/julia-1.2.0-mac64.tar.gz
-    x86_64-apple-darwin14@v1_3@http://cxan.kdr2.com/julia/releases/julia-1.3.0-mac64.tar.gz
-)
-
-for RELEASE in ${RELEASES[@]}; do
-    REL_TARGET=$(echo $RELEASE | cut -d@ -f1)
-    if [ $target != $REL_TARGET ]; then
-        continue
-    fi
-    rm -f *.tar.gz
-    rm -fr julia
-    wget $(echo $RELEASE | cut -d@ -f3)
-    tar xzvf *tar.gz
-    rm -f *.tar.gz
-    mv julia* julia
-    export JULIA_VERSION=$(echo $RELEASE | cut -d@ -f2)
-    if [ $target = x86_64-apple-darwin14 ]; then
-        export JULIA_HOME=$(pwd)/julia/Contents/Resources/julia
-    else
-        export JULIA_HOME=$(pwd)/julia
-        # export JULIA_HOME=/home/kdr2/programs/julia-1.1.0
-    fi
-    make -C Libtask.jl/deps
-done
-
-# https://juliapackaging.github.io/BinaryBuilder.jl/dev/build_tips/#Installing-the-license-file-1
-install_license Libtask.jl/LICENSE
diff --git a/L/Libtask/build_tarballs.jl b/L/Libtask/build_tarballs.jl
index 9a6d881b18e..bb8a7a5f2f7 100644
--- a/L/Libtask/build_tarballs.jl
+++ b/L/Libtask/build_tarballs.jl
@@ -1,52 +1,69 @@
 # Note that this script can accept some limited command-line arguments, run
 # `julia build_tarballs.jl --help` to see a usage message.
-using Pkg
-using BinaryBuilder
+using BinaryBuilder, Pkg
 
-name = "Libtask"
-version = v"0.3.2"
-commit_id = "fbe338053f402d76524d0a01f3796dd7da90b781"
+julia_version = v"1.3.1"
 
-# see https://github.com/JuliaPackaging/BinaryBuilder.jl/issues/336
-# ENV["CI_COMMIT_TAG"] = ENV["TRAVIS_TAG"] = "v" * string(version)
+name = "Libtask"
+version = v"0.4.0"
 
+# Collection of sources required to build Libtask
 sources = [
-    "https://github.com/TuringLang/Libtask.jl.git" => commit_id,
+    DirectorySource("./bundled"),
 ]
 
 # Bash recipe for building across all platforms
-script_file = joinpath(@__DIR__, "build_dylib.sh")
-if !isfile(script_file) # when run generate_buildjl.jl
-    script_file = joinpath(@__DIR__, "L/Libtask/build_dylib.sh")
-end
-script = read(script_file, String)
+script = raw"""
+# create output directory
+mkdir -p "${libdir}"
+
+# compile library
+cd "${WORKSPACE}/srcdir/"
+
+CFLAGS="-I${includedir} -I${includedir}/julia -O2 -shared -std=gnu99 -fPIC"
+if [[ "${target}" == i686-* ]]; then
+  CFLAGS="${CFLAGS} -march=pentium4"
+fi
+if [[ "${target}" == *-mingw* ]]; then
+  CFLAGS="${CFLAGS} -Wl,--export-all-symbols"
+elif [[ "${target}" == *-linux-* ]]; then
+  CFLAGS="${CFLAGS} -Wl,--export-dynamic"
+fi
+
+LDFLAGS="-L${libdir} -ljulia"
+if [[ "${target}" == *-mingw* ]]; then
+  LDFLAGS="${LDFLAGS} -lopenlibm"
+fi
+
+$CC $CFLAGS $LDFLAGS task.c -o "${libdir}/libtask_julia.${dlext}"
+
+# install license
+install_license LICENSE.md
+"""
 
 # These are the platforms we will build for by default, unless further
 # platforms are passed in on the command line
-platforms = [
-    Platform("i686", "linux"; libc="glibc"),
-    Platform("x86_64", "linux"; libc="glibc"),
-    Platform("powerpc64le", "linux"; libc="glibc"),
-    # Platform("armv7l", "linux"; libc="glibc"),
-    Platform("aarch64", "linux"),
-    Platform("x86_64", "macos"),
-    Platform("i686", "windows"),
-    Platform("x86_64", "windows")
-]
+platforms = supported_platforms()
+
+# skip i686 musl builds (not supported by libjulia_jll)
+filter!(p -> !(Sys.islinux(p) && libc(p) == "musl" && arch(p) == "i686"), platforms)
+
+# skip PowerPC builds in Julia 1.3 (not supported by libjulia_jll)
+if julia_version < v"1.4"
+    filter!(p -> !(Sys.islinux(p) && arch(p) == "powerpc64le"), platforms)
+end
 
 # The products that we will ensure are always built
 products = [
-    LibraryProduct("libtask_v1_0", :libtask_v1_0)
-    LibraryProduct("libtask_v1_1", :libtask_v1_1)
-    LibraryProduct("libtask_v1_2", :libtask_v1_2)
-    LibraryProduct("libtask_v1_3", :libtask_v1_3)
+    LibraryProduct("libtask_julia", :libtask_julia),
 ]
 
 # Dependencies that must be installed before this package can be built
 dependencies = [
+    BuildDependency(PackageSpec(name="libjulia_jll", version=julia_version)),
 ]
 
 # Build the tarballs, and possibly a `build.jl` as well.
-# build_file = "products/build_$(name).v$(version).jl"
-build_tarballs(ARGS, name, version, sources,
-               script, platforms, products, dependencies)
+build_tarballs(ARGS, name, version, sources, script, platforms, products, dependencies;
+               julia_compat = "~$(julia_version.major).$(julia_version.minor)",
+               lock_microarchitecture = false)
diff --git a/L/Libtask/bundled/LICENSE.md b/L/Libtask/bundled/LICENSE.md
new file mode 100644
index 00000000000..2b0ea03ff7f
--- /dev/null
+++ b/L/Libtask/bundled/LICENSE.md
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2018 The Turing Language
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/L/Libtask/bundled/task.c b/L/Libtask/bundled/task.c
new file mode 100644
index 00000000000..d5e9160647d
--- /dev/null
+++ b/L/Libtask/bundled/task.c
@@ -0,0 +1,74 @@
+/*
+ task.c
+ task copying (aka continuation) for lightweight processes (symmetric coroutines)
+ */
+
+#include "julia.h"
+
+// Workaround for JuliaLang/julia#32812
+jl_task_t *vanilla_get_current_task(void)
+{
+    jl_ptls_t ptls = jl_get_ptls_states();
+    return (jl_task_t*)ptls->current_task;
+}
+
+
+jl_task_t *jl_enable_stack_copying(jl_task_t *t)
+{
+    if (!t->copy_stack) {
+        jl_ptls_t ptls = jl_get_ptls_states();
+        t->copy_stack = 1;
+        t->bufsz = 0;
+        memcpy(&t->ctx, &ptls->base_ctx, sizeof(t->ctx));
+    }
+    return t;
+}
+
+jl_task_t *jl_clone_task(jl_task_t *t)
+{
+    jl_ptls_t ptls = jl_get_ptls_states();
+    jl_task_t *newt = (jl_task_t*)jl_gc_allocobj(sizeof(jl_task_t)); //  More efficient
+    //jl_task_t *newt = (jl_task_t*)jl_new_task(t->start, t->ssize); //  Less efficient
+    memset(newt, 0, sizeof(jl_task_t));
+    jl_set_typeof(newt, jl_task_type);
+    newt->stkbuf = NULL;
+    newt->gcstack = NULL;
+    JL_GC_PUSH1(&newt);
+
+    newt->state = t->state;
+    newt->start = t->start;
+    newt->tls = jl_nothing;
+    newt->logstate = ptls->current_task->logstate;
+    newt->result = jl_nothing;
+    newt->donenotify = jl_nothing;
+    newt->exception = jl_nothing;
+    newt->backtrace = jl_nothing;
+    newt->eh = t->eh;
+    newt->gcstack = t->gcstack;
+    newt->tid = t->tid;          // TODO: need testing
+    newt->started = t->started;  // TODO: need testing
+
+
+    newt->copy_stack = t->copy_stack;
+    memcpy((void*)newt->ctx.uc_mcontext, (void*)t->ctx.uc_mcontext, sizeof(jl_jmp_buf));
+    newt->queue = t->queue;
+    newt->sticky = t->sticky;
+
+    if (t->stkbuf) {
+        // newt->stkbuf = allocb(t->bufsz);
+        // newt->bufsz = t->bufsz;
+        // memcpy(newt->stkbuf, t->stkbuf, t->bufsz);
+        // workaround, newt and t will get new stkbuf when savestack is called.
+        t->bufsz    = 0;
+        newt->bufsz = 0;
+        newt->stkbuf = t->stkbuf;
+    } else {
+        newt->bufsz = 0;
+        newt->stkbuf = NULL;
+    }
+
+    JL_GC_POP();
+    jl_gc_wb_back(newt);
+
+    return newt;
+}