linux: support building Python and dependencies with musl

I believe this works!

We had to use --disable-shared in various places because we can't
build shared libraries with musl. In theory this should be possible.
I suspect the musl-clang wrapper is passing conflicting
compiler/linker flags or something.

C++ compilation doesn't work with musl. So we disabled C++
compilation in some components. This would be a reasonable change
otherwise as we should never use the C++ bits.

Some hacks were required here and there. For example, OpenSSL
insists on looking for kernel headers, which we don't have. So
we had to disable some OpenSSL functionality to get things to
build. Disabling secure memory is sounds a bit scary. I left a
TODO to track investigating that.

Author: indygreg

build-linux.py

@@ -24,6 +24,7 @@
 
 def bootstrap():
     parser = argparse.ArgumentParser()
+    parser.add_argument('--musl', action='store_true')
     parser.add_argument('--optimized', action='store_true')
 
     args = parser.parse_args()
@@ -40,6 +41,8 @@ def bootstrap():
     os.environ['PATH'] = '%s:%s' % (str(VENV / 'bin'), os.environ['PATH'])
     os.environ['PYTHONPATH'] = str(ROOT)
 
+    if args.musl:
+        os.environ['PYBUILD_MUSL'] = '1'
     if args.optimized:
         os.environ['PYBUILD_OPTIMIZED'] = '1'
 
@@ -58,6 +61,9 @@ def run():
     basename = 'cpython-linux64'
     extra = ''
 
+    if 'PYBUILD_MUSL' in os.environ:
+        basename += '-musl'
+        extra = '-musl'
     if 'PYBUILD_OPTIMIZED' in os.environ:
         basename += '-pgo'
         extra = '-pgo'

cpython-linux/Makefile

@@ -11,6 +11,10 @@ COMMON_DEPENDS := \
 
 PLATFORM := linux64
 
+ifdef PYBUILD_MUSL
+    PLATFORM := $(PLATFORM)-musl
+endif
+
 BASE_TOOLCHAIN_DEPENDS := \
     $(OUTDIR)/binutils-linux64.tar \
     $(OUTDIR)/gcc-linux64.tar \
@@ -22,7 +26,7 @@ TOOLCHAIN_DEPENDS := \
     $(OUTDIR)/musl-linux64.tar \
     $(NULL)
 
-default: $(OUTDIR)/cpython-linux64$(if $(PYBUILD_OPTIMIZED),-pgo,).tar
+default: $(OUTDIR)/cpython-$(PLATFORM)$(if $(PYBUILD_OPTIMIZED),-pgo,).tar
 
 $(OUTDIR)/image-%.tar: $(HERE)/%.Dockerfile $(COMMON_DEPENDS)
 	$(BUILD) image-$*

cpython-linux/build-bdb.sh

@@ -8,8 +8,6 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf db-${BDB_VERSION}.tar.gz
 
@@ -19,7 +17,8 @@ CLFAGS="${EXTRA_TARGET_CFLAGS} -fPIC" CPPFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" ..
     --build=x86_64-unknown-linux-gnu \
     --target=${TARGET} \
     --prefix=/tools/deps \
-    --enable-dbm
+    --enable-dbm \
+    --disable-shared
 
 make -j `nproc`
 make -j `nproc` install DESTDIR=/build/out

cpython-linux/build-bzip2.sh

@@ -15,7 +15,7 @@ pushd bzip2-${BZIP2_VERSION}
 
 make -j `nproc` install \
     AR=/tools/host/bin/${TOOLCHAIN_PREFIX}ar \
-    CC=clang \
+    CC="${CC}" \
     CFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" \
     LDFLAGS="${EXTRA_TARGET_LDFLAGS}" \
     PREFIX=/build/out/tools/deps

cpython-linux/build-cpython.sh

@@ -8,8 +8,6 @@ set -ex
 cd /build
 
 export PATH=/tools/clang-linux64/bin:/tools/host/bin:/tools/deps/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 # configure somehow has problems locating llvm-profdata even though it is in
 # PATH. The macro it is using allows us to specify its path via an
@@ -26,6 +24,8 @@ tar -xf Python-${PYTHON_VERSION}.tar.xz
 cat Setup.local
 mv Setup.local Python-${PYTHON_VERSION}/Modules/Setup.local
 
+cat Makefile.extra
+
 pushd Python-${PYTHON_VERSION}
 
 cp Modules/readline.c Modules/readline-libedit.c
@@ -44,6 +44,12 @@ CFLAGS="-fPIC -I/tools/deps/include -I/tools/deps/include/ncurses"
 CPPFLAGS=$CFLAGS
 LDFLAGS="-L/tools/deps/lib"
 
+if [ "${CC}" = "musl-clang" ]; then
+    CFLAGS="${CFLAGS} -static"
+    CPPFLAGS="${CPPFLAGS} -static"
+    LDFLAGS="${LDFLAGS} -static"
+fi
+
 CONFIGURE_FLAGS="--prefix=/install --with-openssl=/tools/deps --without-ensurepip"
 
 # TODO support --with-lto

cpython-linux/build-gdbm.sh

@@ -8,8 +8,6 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf gdbm-${GDBM_VERSION}.tar.gz
 
@@ -21,6 +19,7 @@ CLFAGS="${EXTRA_TARGET_CFLAGS} -fPIC" CPPFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" ./
     --build=x86_64-unknown-linux-gnu \
     --target=${TARGET} \
     --prefix=/tools/deps \
+    --disable-shared \
     --enable-libgdbm-compat
 
 make -j `nproc`

cpython-linux/build-libedit.sh

@@ -8,21 +8,25 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf libedit-${LIBEDIT_VERSION}.tar.gz
 
 pushd libedit-${LIBEDIT_VERSION}
 
 cflags="${EXTRA_TARGET_CFLAGS} -fPIC -I/tools/deps/include -I/tools/deps/include/ncurses"
 
+# musl doesn't define __STDC_ISO_10646__, so work around that.
+if [ "${CC}" = "musl-clang" ]; then
+    cflags="${cflags} -D__STDC_ISO_10646__=201103L"
+fi
+
 # Install to /tools/deps/libedit so it doesn't conflict with readline's files.
 CLFAGS="${cflags}" CPPFLAGS="${cflags}" LDFLAGS="-L/tools/deps/lib" \
     ./configure \
         --build=x86_64-unknown-linux-gnu \
         --host=${TARGET} \
         --prefix=/tools/deps/libedit \
+        --disable-shared
 
 make -j `nproc`
 make -j `nproc` install DESTDIR=/build/out

cpython-linux/build-libffi.sh

@@ -8,8 +8,6 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf libffi-${LIBFFI_VERSION}.tar.gz
 
@@ -18,7 +16,8 @@ pushd libffi-${LIBFFI_VERSION}
 CFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" CPPFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" ./configure \
     --build=x86_64-unknown-linux-gnu \
     --host=${TARGET} \
-    --prefix=/tools/deps
+    --prefix=/tools/deps \
+    --disable-shared
 
 make -j `nproc`
 make -j `nproc` install DESTDIR=/build/out

cpython-linux/build-ncurses.sh

@@ -8,8 +8,6 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf ncurses-${NCURSES_VERSION}.tar.gz
 
@@ -18,6 +16,7 @@ pushd ncurses-${NCURSES_VERSION}
 CFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" ./configure \
     --build=x86_64-unknown-linux-gnu \
     --host=${TARGET} \
-    --prefix=/tools/deps
+    --prefix=/tools/deps \
+    --without-cxx
 make -j `nproc`
 make -j `nproc` install DESTDIR=/build/out

cpython-linux/build-openssl.sh

@@ -8,14 +8,19 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf openssl-${OPENSSL_VERSION}.tar.gz
 
 pushd openssl-${OPENSSL_VERSION}
 
-/usr/bin/perl ./Configure --prefix=/tools/deps linux-x86_64
+# musl is missing support for various primitives.
+# TODO disable secure memory is a bit scary. We should look into a proper
+# workaround.
+if [ "${CC}" = "musl-clang" ]; then
+    EXTRA_FLAGS="no-async -DOPENSSL_NO_ASYNC -D__STDC_NO_ATOMICS__=1 no-engine -DOPENSSL_NO_SECURE_MEMORY "
+fi
+
+/usr/bin/perl ./Configure --prefix=/tools/deps linux-x86_64 no-shared ${EXTRA_FLAGS}
 
 make -j `nproc`
 make -j `nproc` install DESTDIR=/build/out

cpython-linux/build-readline.sh

@@ -8,8 +8,6 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf readline-${READLINE_VERSION}.tar.gz
 
@@ -20,6 +18,7 @@ CLFAGS="${EXTRA_TARGET_CFLAGS} -fPIC" CPPFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" LD
         --build=x86_64-unknown-linux-gnu \
         --host=${TARGET} \
         --prefix=/tools/deps \
+        --disable-shared \
         --with-curses
 
 make -j `nproc`

cpython-linux/build-sqlite.sh

@@ -8,13 +8,13 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf sqlite-autoconf-3280000.tar.gz
 pushd sqlite-autoconf-3280000
 
-CFLAGS="-fPIC" CPPFLAGS="-fPIC" ./configure --prefix /tools/deps
+CFLAGS="-fPIC" CPPFLAGS="-fPIC" ./configure \
+    --prefix /tools/deps \
+    --disable-shared
 
 make -j `nproc`
 make -j `nproc` install DESTDIR=/build/out

cpython-linux/build-tcltk.sh

@@ -8,8 +8,6 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf tcl8.6.9-src.tar.gz
 

cpython-linux/build-uuid.sh

@@ -8,13 +8,13 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf libuuid-${UUID_VERSION}.tar.gz
 pushd libuuid-${UUID_VERSION}
 
-CFLAGS="-fPIC" CPPFLAGS="-fPIC" ./configure --prefix=/tools/deps
+CFLAGS="-fPIC" CPPFLAGS="-fPIC" ./configure \
+    --prefix=/tools/deps \
+    --disable-shared
 
 make -j `nproc`
 make -j `nproc` install DESTDIR=/build/out

cpython-linux/build-xz.sh

@@ -8,15 +8,14 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf xz-${XZ_VERSION}.tar.gz
 
 pushd xz-${XZ_VERSION}
 
 CFLAGS="-fPIC" CPPFLAGS="-fPIC" CCASFLAGS="-fPIC" ./configure \
     --prefix=/tools/deps \
+    --disable-shared \
     --disable-xz \
     --disable-xzdec \
     --disable-lzmadec \

cpython-linux/build-zlib.sh

@@ -8,8 +8,6 @@ set -ex
 cd /build
 
 export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
-export CC=clang
-export CXX=clang++
 
 tar -xf zlib-${ZLIB_VERSION}.tar.gz