Build libc++/libc++abi for wasm32-wasi

Do a standalone build of libcxx/libcxxabi, for wasm32-wasi. libcxx requires a libc, and thus this requires a new build dependency on wasi-libc. wasi-libc is not currently available for wasm64, so limit the build to wasm32. This introduces two new binary packages: - libc++-${LLVM_VERSION}-dev-wasm32 - libc++abi-${LLVM_VERSION}-dev-wasm32 There isn't currently a naming convention in Debian for WebAssembly. Use a "-dev-wasm32" suffix, which makes it consistent with packages such as "libc6-dev-i386" and "libstd-rust-dev-wasm32". Given these builds are specific to WASI, it can be argued that the names should be something like "-dev-wasm32-wasi", or simplified to "-dev-wasi" (not very future proof) or "-dev-wasi32" (not something upstream uses). Something to think through later on. WebAssembly only supports shared linking, hence why we -dev packages are provided, shipping development headers and static archives.
2025-07-27 09:50:53 +00:00 · 2022-11-13 12:14:06 +02:00 · 2022-11-13 12:14:06 +02:00 · 97d60707ed
commit 97d60707ed
parent 9459395c21
7 changed files with 159 additions and 8 deletions
--- a/debian/control
+++ b/debian/control
@ -24,6 +24,7 @@ Build-Depends: debhelper (>= 10.0), cmake, ninja-build,
    libpfm4-dev [linux-any], python3-setuptools, libz3-dev,
    llvm-spirv-14 [ amd64 arm64 armel armhf mips64el mipsel ppc64el s390x ] <!stage1> | hello [!i386],
    spirv-tools [ linux-any ] | hello [ !i386],
+    wasi-libc,
    libcurl4-dev,
    libgrpc++-dev [amd64 arm64 armel armhf mips64el mipsel ppc64 ppc64el powerpc riscv64 s390x],
    protobuf-compiler-grpc [amd64 arm64 armel armhf mips64el mipsel ppc64 ppc64el powerpc riscv64 s390x],
@ -648,6 +649,29 @@ Description: LLVM C++ Standard library (development files)
     as exception objects, rtti and memory allocation.
   * Extensive unit tests.

+Package: libc++-14-dev-wasm32
+Section: libdevel
+Architecture: all
+Multi-Arch: foreign
+Depends: wasi-libc, libc++abi-14-dev-wasm32, ${misc:Depends}
+Provides: libc++-x.y-dev-wasm32
+Conflicts: libc++-x.y-dev-wasm32
+Replaces: libc++-x.y-dev-wasm32
+Description: LLVM C++ Standard library (WASI)
+ libc++ is another implementation of the C++ standard library
+ .
+ Features and Goals
+ .
+   * Correctness as defined by the C++ standards.
+   * Fast execution.
+   * Minimal memory use.
+   * Fast compile times.
+   * ABI compatibility with gcc's libstdc++ for some low-level features such
+     as exception objects, rtti and memory allocation.
+   * Extensive unit tests.
+ .
+ This package provides a version for the 32-bit WebAssembly System Interface.
+
 # ------------- libcxxabi -------------

 Package: libc++abi1-14
@ -687,6 +711,25 @@ Description: LLVM low level support for a standard C++ library (development file
   * Correctness as defined by the C++ standards.
   * Provide a portable sublayer to ease the porting of libc++

+Package: libc++abi-14-dev-wasm32
+Section: libdevel
+Architecture: all
+Multi-Arch: foreign
+Depends: wasi-libc, ${misc:Depends}
+Provides: libc++abi-x.y-dev-wasm32
+Conflicts: libc++abi-x.y-dev-wasm32
+Replaces: libc++abi-x.y-dev-wasm32
+Description: LLVM low level support for a standard C++ library (WASI)
+ libc++abi is another implementation of low level support for a standard C++
+ library.
+ .
+ Features and Goals
+ .
+   * Correctness as defined by the C++ standards.
+   * Provide a portable sublayer to ease the porting of libc++
+ .
+ This package provides a version for the 32-bit WebAssembly System Interface.
+
 # ------------- libclc -------------

 Package: libclc-14
--- a/debian/libc++-X.Y-dev-wasm32.install.in
+++ b/debian/libc++-X.Y-dev-wasm32.install.in
@ -0,0 +1,3 @@
+usr/lib/llvm-@LLVM_VERSION@/lib/wasm32-wasi/libc++.a
+usr/lib/llvm-@LLVM_VERSION@/include/wasm32-wasi/c++/
+usr/lib/llvm-@LLVM_VERSION@/include/wasm32-wasi/c++/v1/
--- a/debian/libc++-X.Y-dev-wasm32.links.in
+++ b/debian/libc++-X.Y-dev-wasm32.links.in
@ -0,0 +1,2 @@
+usr/lib/llvm-@LLVM_VERSION@/lib/wasm32-wasi/libc++.a /usr/lib/wasm32-wasi/libc++.a
+usr/lib/llvm-@LLVM_VERSION@/include/wasm32-wasi/c++/v1 /usr/include/wasm32-wasi/c++/v1
--- a/debian/libc++abi-X.Y-dev-wasm32.install.in
+++ b/debian/libc++abi-X.Y-dev-wasm32.install.in
@ -0,0 +1 @@
+usr/lib/llvm-@LLVM_VERSION@/lib/wasm32-wasi/libc++abi.a
--- a/debian/libc++abi-X.Y-dev-wasm32.links.in
+++ b/debian/libc++abi-X.Y-dev-wasm32.links.in
@ -0,0 +1 @@
+usr/lib/llvm-@LLVM_VERSION@/lib/wasm32-wasi/libc++abi.a /usr/lib/wasm32-wasi/libc++abi.a
--- a/debian/qualify-clang.sh
+++ b/debian/qualify-clang.sh
@ -1361,22 +1361,34 @@ fi
 if dpkg -l|grep -q wasi-libc; then
    cat <<EOF > printf.c
    #include <stdio.h>
-    int main(int argc, char *argv[])
-    {
-    printf("%s\n", "Hello world!");
+    int main(int argc, char *argv[]) {
+      printf("%s\n", "Hello World!");
    }
 EOF
-    clang-$VERSION -target wasm32-unknown-wasi -o printf printf.c
+    # wasi-libc supports only wasm32 right now
+    clang-$VERSION -target wasm32-wasi -o printf printf.c
    file printf &> foo.log
    if ! grep -q "WebAssembly" foo.log; then
        echo "the generated file isn't a WebAssembly file?"
        exit 1
    fi
    rm -f printf.c printf
+
+    cat <<EOF > cout.cpp
+    #include <iostream>
+    int main() {
+      std::cout << "Hello World!" << std::endl;
+    }
+EOF
+    # libcxx requires wasi-libc, which only exists for wasm32 right now
+    clang++-$VERSION --target=wasm32-wasi -o cout cout.cpp
+    file cout &> foo.log
+    if ! grep -q "WebAssembly" foo.log; then
+        echo "the generated file isn't a WebAssembly file?"
+        exit 1
+    fi
+    rm -f cout.cpp cout
 fi
-echo '#include <algorithm>' > foo.cpp
-# Fails for now
-clang++-$VERSION --target=wasm32-wasi -o foo.o -c foo.cpp||true

 echo '
 #include <vector>
--- a/debian/rules
+++ b/debian/rules
@ -740,8 +740,89 @@ build-wasm/compiler-rt-%:
 		-DCOMPILER_RT_OS_DIR=wasi
 	ninja -C "$@" $(NJOBS) $(VERBOSE)

+build-wasm/libcxx-%-wasi: cpu = $(@:build-wasm/libcxx-%-wasi=%)
+build-wasm/libcxx-%-wasi: build-wasm/compiler-rt-%
+	@echo "Building libcxx for $(cpu)"
+	@echo "Using cmake: $(CMAKE_BIN)"
+
+	# We need a functioning clang, which in turn requires a linker. We
+	# patch clang to use a versioned wasm-ld (cf. wasm-ld-path.diff), so
+	# create wasm-ld-$(LLVM_VERSION) in the stage2 bin dir manually.
+	cp $(STAGE_2_BIN_DIR)/wasm-ld $(STAGE_2_BIN_DIR)/wasm-ld-$(LLVM_VERSION)
+
+	# We need a wasm compiler-rt. Depend on the make target that builds it,
+	# and manually copy it to the stage2 lib dir from there
+	mkdir -p \
+	   $(STAGE_2_LIB_DIR)/clang/$(LLVM_VERSION_FULL)/lib/wasi/
+	cp build-wasm/compiler-rt-$(cpu)/lib/wasi/libclang_rt.builtins-$(cpu).a \
+	   $(STAGE_2_LIB_DIR)/clang/$(LLVM_VERSION_FULL)/lib/wasi/
+
+	# Notes:
+	# - Uses $(LDFLAGS) instead of $(STAGE_2_LDFLAGS), because wasm-ld does not
+	#   support --build-id yet. Upstream is working on it, cf. D107662.
+	# - Pass -fno-stack-protector to disable -fstack-protector-strong that is
+	#   passed by default, as this is not supported yet in WebAssembly, cf.
+	#   https://github.com/WebAssembly/wasi-libc/issues/157
+	# - Use llvm-ar and llvm-ranlib, as binutils does not currently support
+	#   WebAssembly and creates invalid indexes.
+	# - Use LLVM_LIBDIR_SUFFIX to install to /usr/lib/wasm32-wasi. To be
+	#   replaced by CMAKE_INSTALL_LIBDIR=lib/$(cpu)-wasi when D130586
+	#   ships.
+	mkdir -p "$@"
+	$(CMAKE_BIN) -B "$@" -S runtimes \
+		-G $(GENERATOR) \
+		$(SCCACHE_CMAKE) \
+		-DCMAKE_C_COMPILER_WORKS=ON \
+		-DCMAKE_CXX_COMPILER_WORKS=ON \
+		-DLLVM_COMPILER_CHECKED=ON \
+		-DCMAKE_C_COMPILER_TARGET=$(cpu)-unknown-wasi \
+		-DCMAKE_CXX_COMPILER_TARGET=$(cpu)-unknown-wasi \
+		-DCMAKE_ASM_COMPILER_TARGET=$(cpu)-unknown-wasi \
+		-DCMAKE_C_COMPILER=$(STAGE_2_BIN_DIR)/clang \
+		-DCMAKE_CXX_COMPILER=$(STAGE_2_BIN_DIR)/clang++ \
+		-DCMAKE_AR=$(STAGE_2_BIN_DIR)/llvm-ar \
+		-DCMAKE_RANLIB=$(STAGE_2_BIN_DIR)/llvm-ranlib \
+		-DCMAKE_C_FLAGS="$(opt_flags) $(STAGE_2_CFLAGS) -fno-stack-protector" \
+		-DCMAKE_CXX_FLAGS="$(opt_flags) $(STAGE_2_CXXFLAGS) -fno-stack-protector" \
+		-DCMAKE_SHARED_LINKER_FLAGS="$(LDFLAGS) -L$(STAGE_2_LIB_DIR)" \
+		-DCMAKE_MODULE_LINKER_FLAGS="$(LDFLAGS) -L$(STAGE_2_LIB_DIR)" \
+		-DCMAKE_EXE_LINKER_FLAGS="$(LDFLAGS) -L$(STAGE_2_LIB_DIR)" \
+		-DCMAKE_INSTALL_PREFIX=/usr/lib/llvm-$(LLVM_VERSION) \
+		-DCMAKE_INSTALL_INCLUDEDIR=include/$(cpu)-wasi \
+		-DLLVM_LIBDIR_SUFFIX=/$(cpu)-wasi \
+		-DLLVM_CONFIG=$(STAGE_2_BIN_DIR)/llvm-config \
+		-DLLVM_ENABLE_RUNTIMES="libcxx;libcxxabi" \
+		-DLIBCXX_USE_COMPILER_RT=ON \
+		-DLIBCXXABI_USE_COMPILER_RT=ON \
+		-DLIBCXX_ENABLE_STATIC_ABI_LIBRARY=ON \
+		-DLIBCXX_STATICALLY_LINK_ABI_IN_STATIC_LIBRARY=ON \
+		-DLIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY=OFF \
+		-DCMAKE_BUILD_TYPE=RelWithDebugInfo \
+		-DLIBCXX_CXX_ABI=libcxxabi \
+		-DLIBCXX_ABI_VERSION=2 \
+		-DLIBCXX_HAS_MUSL_LIBC:BOOL=ON \
+		-DLIBCXX_ENABLE_SHARED:BOOL=OFF \
+		-DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY:BOOL=OFF \
+		-DLIBCXX_ENABLE_EXCEPTIONS:BOOL=OFF \
+		-DLIBCXX_ENABLE_FILESYSTEM:BOOL=OFF \
+		-DLIBCXX_ENABLE_THREADS:BOOL=OFF \
+		-DLIBCXX_HAS_PTHREAD_API:BOOL=OFF \
+		-DLIBCXX_HAS_EXTERNAL_THREAD_API:BOOL=OFF \
+		-DLIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY:BOOL=OFF \
+		-DLIBCXXABI_ENABLE_SHARED:BOOL=OFF \
+		-DLIBCXXABI_ENABLE_EXCEPTIONS:BOOL=OFF \
+		-DLIBCXXABI_SILENT_TERMINATE:BOOL=ON \
+		-DLIBCXXABI_ENABLE_THREADS:BOOL=OFF \
+		-DLIBCXXABI_HAS_PTHREAD_API:BOOL=OFF \
+		-DLIBCXXABI_HAS_EXTERNAL_THREAD_API:BOOL=OFF \
+		-DLIBCXXABI_BUILD_EXTERNAL_THREAD_LIBRARY:BOOL=OFF
+	ninja -C "$@" $(NJOBS) $(VERBOSE)
+
+# Build compiler-rt for wasm32 and wasm64. Build libcxx only for wasm32, as
+# libcxx requires wasi-libc, which only exists for wasm32 right now.
 debian-wasm-build: \
  build-wasm/compiler-rt-wasm32 \
+  build-wasm/libcxx-wasm32-wasi \
  build-wasm/compiler-rt-wasm64
 	touch $@

@ -902,6 +983,7 @@ endif

 	DESTDIR=$(DEB_INST) ninja $(VERBOSE) -C build-wasm/compiler-rt-wasm32 install
 	DESTDIR=$(DEB_INST) ninja $(VERBOSE) -C build-wasm/compiler-rt-wasm64 install
+	DESTDIR=$(DEB_INST) ninja $(VERBOSE) -C build-wasm/libcxx-wasm32-wasi install

 # Rename binaries
 	mkdir -p $(DEB_INST)/usr/bin/
@ -1055,7 +1137,7 @@ ifeq ($(shell dpkg --compare-versions $(shell dpkg-query -W -f '$${Version}' bin
 else
 	# GNU strip doesn't recognize WebAssembly binaries, and actually corrupts them.
 	# llvm-strip (as of 15.0.2) fails with --strip-debug (but works with --strip-all)
-	dh_strip -a -v -Xlibclang_rt.builtins-wasm32.a -Xlibclang_rt.builtins-wasm64.a
+	dh_strip -a -v -Xlibclang_rt.builtins-wasm32.a -Xlibclang_rt.builtins-wasm64.a -Xusr/lib/wasm32-wasi
 endif

 override_dh_install:
@ -1085,6 +1167,13 @@ override_dh_installdeb:

 # Remove some libc++ abi files in the libc++ file. See bug #969274
 	rm -f $(CURDIR)/debian/libc++-$(LLVM_VERSION)-dev/usr/lib/llvm-$(LLVM_VERSION)/include/c++/__cxxabi_config.h $(CURDIR)/debian/libc++-$(LLVM_VERSION)-dev/usr/lib/llvm-$(LLVM_VERSION)/include/c++/cxxabi.h
+
+	mkdir -p $(CURDIR)/debian/libc++abi-$(LLVM_VERSION)-dev-wasm32/usr/lib/llvm-$(LLVM_VERSION)/include/wasm32-wasi/c++/v1
+	mv $(CURDIR)/debian/libc++-$(LLVM_VERSION)-dev-wasm32/usr/lib/llvm-$(LLVM_VERSION)/include/wasm32-wasi/c++/v1/__cxxabi_config.h \
+	   $(CURDIR)/debian/libc++abi-$(LLVM_VERSION)-dev-wasm32/usr/lib/llvm-$(LLVM_VERSION)/include/wasm32-wasi/c++/v1/__cxxabi_config.h
+	mv $(CURDIR)/debian/libc++-$(LLVM_VERSION)-dev-wasm32/usr/lib/llvm-$(LLVM_VERSION)/include/wasm32-wasi/c++/v1/cxxabi.h \
+	   $(CURDIR)/debian/libc++abi-$(LLVM_VERSION)-dev-wasm32/usr/lib/llvm-$(LLVM_VERSION)/include/wasm32-wasi/c++/v1/cxxabi.h
+
 # Remove auto generated python pyc
 	find $(CURDIR)/debian/llvm-$(LLVM_VERSION)-tools/usr/lib/llvm-$(LLVM_VERSION)/ -name '*.pyc' | xargs -r rm -f
				`@ -0,0 +1 @@`
				`usr/lib/llvm-@LLVM_VERSION@/lib/wasm32-wasi/libc++abi.a`