mktoolchain.sh

#!/usr/bin/env bash
set -e
set -o pipefail

SRCDIR=/srcdir
BUILDDIR=/build
PKGDIR=/toolchain

die() {
  echo "die: $*" 1>&2
  exit 1
}

pacman-key --refresh-keys
pacman -Syy --noconfirm python binutils gcc bison cmake ninja make libunistring patch

mkdir -p ${SRCDIR}/binutils
curl http://ftp.gnu.org/gnu/binutils/binutils-2.26.tar.bz2 | tar xj -C ${SRCDIR}/binutils --strip-components=1
mkdir -p ${SRCDIR}/llvm
curl http://llvm.org/releases/3.8.0/llvm-3.8.0.src.tar.xz | tar xJ -C ${SRCDIR}/llvm --strip-components=1
mkdir -p ${SRCDIR}/llvm/tools/clang
curl http://llvm.org/releases/3.8.0/cfe-3.8.0.src.tar.xz | tar xJ -C ${SRCDIR}/llvm/tools/clang --strip-components=1
mkdir -p ${SRCDIR}/llvm/projects/compiler-rt
curl http://llvm.org/releases/3.8.0/compiler-rt-3.8.0.src.tar.xz | tar xJ -C ${SRCDIR}/llvm/projects/compiler-rt --strip-components=1
mkdir -p ${SRCDIR}/llvm/projects/libcxx
curl http://llvm.org/releases/3.8.0/libcxx-3.8.0.src.tar.xz | tar xJ -C ${SRCDIR}/llvm/projects/libcxx --strip-components=1
mkdir -p ${SRCDIR}/llvm/projects/libcxxabi
curl http://llvm.org/releases/3.8.0/libcxxabi-3.8.0.src.tar.xz | tar xJ -C ${SRCDIR}/llvm/projects/libcxxabi --strip-components=1
mkdir -p ${SRCDIR}/llvm/projects/libunwind
curl http://llvm.org/releases/3.8.0/libunwind-3.8.0.src.tar.xz | tar xJ -C ${SRCDIR}/llvm/projects/libunwind --strip-components=1
mkdir -p ${SRCDIR}/musl
curl http://www.musl-libc.org/releases/musl-1.1.14.tar.gz | tar xz -C ${SRCDIR}/musl --strip-components=1

pushd ${SRCDIR}/llvm/tools/clang
patch -p1 <<EOF
diff --git a/include/clang/Driver/ToolChain.h b/include/clang/Driver/ToolChain.h
index 7e68d0a..424d9cc 100644
--- a/include/clang/Driver/ToolChain.h
+++ b/include/clang/Driver/ToolChain.h
@@ -258,0 +259,4 @@ public:
+  virtual CXXStdlibType GetDefaultCXXStdlibType() const {
+    return ToolChain::CST_Libcxx;
+  }
+
diff --git a/lib/Driver/ToolChain.cpp b/lib/Driver/ToolChain.cpp
index cbbd485..af5332a 100644
--- a/lib/Driver/ToolChain.cpp
+++ b/lib/Driver/ToolChain.cpp
@@ -547 +547 @@ ToolChain::CXXStdlibType ToolChain::GetCXXStdlibType(const ArgList &Args) const{
-  return ToolChain::CST_Libstdcxx;
+  return GetDefaultCXXStdlibType();
@@ -610,0 +611,2 @@ void ToolChain::AddCXXStdlibLibArgs(const ArgList &Args,
+    CmdArgs.push_back("-lc++abi");
+    CmdArgs.push_back("-lunwind");
diff --git a/lib/Driver/ToolChains.h b/lib/Driver/ToolChains.h
index f940e58..fd4b23e 100644
--- a/lib/Driver/ToolChains.h
+++ b/lib/Driver/ToolChains.h
@@ -803,0 +804,7 @@ public:
+  CXXStdlibType GetDefaultCXXStdlibType() const override {
+    return ToolChain::CST_Libstdcxx;
+  }
+  RuntimeLibType GetDefaultRuntimeLibType() const override {
+    return ToolChain::RLT_CompilerRT;
+  }
+
EOF
popd

rm -rf ${BUILDDIR}/build-clang+llvm-x86_64-bootstrap && mkdir -p ${BUILDDIR}/build-clang+llvm-x86_64-bootstrap
pushd ${BUILDDIR}/build-clang+llvm-x86_64-bootstrap
cmake -GNinja \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_INSTALL_PREFIX=${BUILDDIR}/clang+llvm-x86_64-bootstrap \
  -DLLVM_INSTALL_TOOLCHAIN_ONLY=ON \
  ${SRCDIR}/llvm
ninja install
popd

rm -rf ${BUILDDIR}/build-binutils && mkdir -p ${BUILDDIR}/build-binutils
pushd ${BUILDDIR}/build-binutils
${SRCDIR}/binutils/configure \
  CC=${BUILDDIR}/clang+llvm-x86_64-bootstrap/bin/clang \
  CXX=${BUILDDIR}/clang+llvm-x86_64-bootstrap/bin/clang++ \
  CXXFLAGS='-stdlib=libc++ -I${BUILDDIR}/clang+llvm-x86_64-bootstrap/include/c++/v1' \
  LDFLAGS='-L${BUILDDIR}/clang+llvm-x86_64-bootstrap/lib -Wl,-rpath,'"'"'$\\$$\$$\\$$\$$ORIGIN/../lib'"'"' -Wl,-z,origin' \
  --prefix=${PKGDIR}/clang+llvm-x86_64-archlinux \
  --enable-deterministic-archives \
  --enable-gold \
  --enable-plugins \
  --disable-ld \
  --disable-werror \
  --with-sysroot=${PKGDIR}/clang+llvm-x86_64-archlinux
make
make install
popd

pushd ${PKGDIR}/clang+llvm-x86_64-archlinux
rm -rf include lib share x86_64-pc-linux-gnu
popd

rm -rf ${BUILDDIR}/build-clang+llvm-x86_64-archlinux && mkdir -p ${BUILDDIR}/build-clang+llvm-x86_64-archlinux
pushd ${BUILDDIR}/build-clang+llvm-x86_64-archlinux
cmake -GNinja \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_C_COMPILER=${BUILDDIR}/clang+llvm-x86_64-bootstrap/bin/clang \
  -DCMAKE_CXX_COMPILER=${BUILDDIR}/clang+llvm-x86_64-bootstrap/bin/clang++ \
  -DCMAKE_INSTALL_PREFIX=${PKGDIR}/clang+llvm-x86_64-archlinux \
  -DCMAKE_INSTALL_RPATH='$ORIGIN/../lib' \
  -DLLVM_ENABLE_TIMESTAMPS=OFF \
  -DLLVM_ENABLE_LIBCXX=ON \
  -DLLVM_ENABLE_LIBCXXABI=ON \
  -DLLVM_BINUTILS_INCDIR=/binutils/include \
  -DLLVM_INSTALL_TOOLCHAIN_ONLY=ON \
  -DLLVM_USE_HOST_TOOLS=ON \
  -DLIBCXX_HAS_MUSL_LIBC=ON \
  -DLIBCXXABI_USE_LLVM_UNWINDER=ON \
  -DDEFAULT_SYSROOT=${PKGDIR}/clang+llvm-x86_64-archlinux \
  ${SRCDIR}/llvm
ninja install
popd

rm -rf ${BUILDDIR}/build-musl && mkdir -p ${BUILDDIR}/build-musl
pushd ${BUILDDIR}/build-musl
${SRCDIR}/musl/configure \
  CC=${BUILDDIR}/clang+llvm-x86_64-bootstrap/bin/clang \
  LIBCC=-lclang_rt.builtins-x86_64 \
  LDFLAGS=-L${PKGDIR}/clang+llvm-x86_64-archlinux/lib/clang/3.8.0/lib/linux \
  --prefix=${PKGDIR}/clang+llvm-x86_64-archlinux \
  --disable-wrapper
make install
popd

rm -rf ${BUILDDIR}/build-crt && mkdir -p ${BUILDDIR}/build-crt
pushd ${BUILDDIR}/build-crt
touch crtbegin.c crtend.c
${PKGDIR}/clang+llvm-x86_64-archlinux/bin/clang crtbegin.c -c -o crtbegin.o
${PKGDIR}/clang+llvm-x86_64-archlinux/bin/clang crtend.c -c -o crtend.o
install crtbegin.o crtend.o ${PKGDIR}/clang+llvm-x86_64-archlinux/lib/clang/3.8.0/
popd

Note: crt{begin,end}S.o are required, e.g. after line 139:

touch crtbeginS.c crtendS.c
${PKGDIR}/bin/clang crtbeginS.c -c -o crtbeginS.o
${PKGDIR}/bin/clang crtendS.c -c -o crtendS.o
install crtbeginS.o crtendS.o ${PKGDIR}/lib/clang/3.8.0/