Merge branch 'main' into sy/old-wasip3

.github/actions/install-deps/action.yml

@@ -7,7 +7,7 @@ runs:
     - name: Setup `wasmtime` for tests
       uses: bytecodealliance/actions/wasmtime/setup@v1
       with:
-        version: "29.0.1"
+        version: "41.0.3"
     - name: Install ccache, ninja (macOS)
       run: brew install ccache ninja
       if: runner.os == 'macOS'

.github/workflows/main.yml

@@ -155,15 +155,21 @@ jobs:
           key: 0-cache-${{ matrix.artifact }}-${{ github.run_id }}
 
   build-only-sysroot:
-    name: Build only sysroot
+    name: Build only sysroot - ${{ matrix.name }}
     runs-on: ubuntu-24.04
+    strategy:
+      matrix:
+        include:
+          - name: default
+          - name: exceptions
+            defines: -DWASI_SDK_EXCEPTIONS=ON
     steps:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - uses: ./.github/actions/checkout
       - uses: ./.github/actions/install-deps
-      - run: cargo install wasm-component-ld@0.5.12
+      - run: cargo install wasm-component-ld@0.5.21
       - run: sudo apt-get update -y && sudo apt-get install -y clang-20 lld-20
       - run: |
           cmake -G Ninja -B build -S . \
@@ -172,7 +178,8 @@ jobs:
             -DWASI_SDK_INCLUDE_TESTS=ON \
             -DWASI_SDK_CPU_CFLAGS="" \
             -DCMAKE_C_LINKER_DEPFILE_SUPPORTED=OFF \
-            -DCMAKE_CXX_LINKER_DEPFILE_SUPPORTED=OFF
+            -DCMAKE_CXX_LINKER_DEPFILE_SUPPORTED=OFF \
+            ${{ matrix.defines }}
       - run: ninja -C build
       - run: ctest --output-on-failure --parallel 10 --test-dir build/tests
 

CppExceptions.md

@@ -0,0 +1,60 @@
+# Support for C++ Exceptions
+
+The released artifacts for wasi-sdk at this time do not support C++ exceptions.
+LLVM and Clang, however, have support for C++ exceptions in WebAssembly and this
+is intended to serve as documentation of the current state of affairs of using
+C++ exceptions. It should be noted though that the current status of C++
+exceptions support is not intended to be the final state of support, and this is
+all continuing to be iterated on over time.
+
+## Building wasi-sdk with exceptions
+
+When building the sysroot with wasi-sdk you can pass `-DWASI_SDK_EXCEPTIONS=ON`
+to enable support for C++ exceptions. For example:
+
+```shell script
+$ cmake -G Ninja -B build/sysroot -S . \
+    -DCMAKE_TOOLCHAIN_FILE=$path/to/wasi-sdk-p1.cmake \
+    -DWASI_SDK_EXCEPTIONS=ON
+```
+
+The C++ standard library will be compiled with support for exceptions for the
+desired targets and the resulting sysroot supports using exceptions.
+
+## Compiling code with C++ exceptions
+
+Currently extra compilation flags are required to fully support C++ exceptions.
+Without these flags programs using C++ exceptions will not work correctly:
+
+* `-fwasm-exceptions` - needed to enable the WebAssembly exception-handling
+  proposal.
+* `-mllvm -wasm-use-legacy-eh=false` - indicates that the standard WebAssembly
+  exception-handling instructions should be used.
+* `-lunwind` - links in support for unwinding which C++ exceptions requires.
+
+This can be specified for example with:
+
+```shell script
+$ export CFLAGS="-fwasm-exceptions -mllvm -wasm-use-legacy-eh=false"
+$ export LDFLAGS="-lunwind"
+```
+
+## Limitations
+
+Currently C++ exceptions support in wasi-sdk does not support shared libraries.
+Fixing this will require resolving some miscellaneous build issues in this
+repository itself.
+
+## Future Plans
+
+There are a few tracking issues with historical discussion about C++ exceptions
+support in wasi-sdk such as [#334](https://github.com/WebAssembly/wasi-sdk/issues/334)
+and [#565](https://github.com/WebAssembly/wasi-sdk/issues/565). The major
+remaining items are:
+
+* Figure out support for shared libraries.
+* Determine how to ship a sysroot that supports both with-and-without
+  exceptions.
+* Figure out how to avoid the need for extra compiler flags when using
+  exceptions.
+* Figure out if a new wasm target is warranted.

README.md

@@ -44,6 +44,7 @@ The Wasm-sdk's build process needs some packages :
 * `clang`
 * `ninja`
 * `python3`
+* `cargo`
 
 Please refer to your OS documentation to install those packages.
 
@@ -87,6 +88,10 @@ in compiling WebAssembly code. Supported CMake flags are:
 * `-DWASI_SDK_INCLUDE_TESTS=ON` - used for building tests.
 * `-DWASI_SDK_CPU_CFLAGS=..` - used to specify CFLAGS to tweak wasm features
   to enable/disable. The default is `-mcpu=lime1`.
+* `-DWASI_SDK_LTO=ON` - whether to enable/disable builds of LTO-capable
+  libraries as part of the build.
+* `-DWASI_SDK_EXCEPTIONS=ON` - whether to enable/disable support for C++
+  exceptions, see [CppExceptions.md](./CppExceptions.md) for more information.
 * `-DWASI_SDK_TEST_HOST_TOOLCHAIN=ON` - test the host toolchain's wasi-libc and
   sysroot libraries, don't build or use fresh libraries for tests.
 * `-DWASI_SDK_TARGETS=..` - a list of targets to build, by default all WASI

cmake/wasi-sdk-sysroot.cmake

@@ -23,7 +23,8 @@ find_program(MAKE make REQUIRED)
 option(WASI_SDK_DEBUG_PREFIX_MAP "Pass `-fdebug-prefix-map` for built artifacts" ON)
 option(WASI_SDK_INCLUDE_TESTS "Whether or not to build tests by default" OFF)
 option(WASI_SDK_INSTALL_TO_CLANG_RESOURCE_DIR "Whether or not to modify the compiler's resource directory" OFF)
-option(WASI_SDK_LTO "Whether or not to build LTO assets" OFF)
+option(WASI_SDK_LTO "Whether or not to build LTO assets" ON)
+option(WASI_SDK_EXCEPTIONS "Whether or not C++ exceptions are enabled" OFF)
 set(WASI_SDK_CPU_CFLAGS "-mcpu=lime1" CACHE STRING "CFLAGS to specify wasm features to enable")
 
 set(wasi_tmp_install ${CMAKE_CURRENT_BINARY_DIR}/install)
@@ -89,6 +90,8 @@ function(define_compiler_rt target)
         -DCOMPILER_RT_BUILD_GWP_ASAN=OFF
         -DCMAKE_C_COMPILER_TARGET=${target}
         -DCMAKE_C_FLAGS=${WASI_SDK_CPU_CFLAGS}
+        -DCMAKE_CXX_FLAGS=${WASI_SDK_CPU_CFLAGS}
+        -DCMAKE_ASM_FLAGS=${WASI_SDK_CPU_CFLAGS}
         -DCMAKE_INSTALL_PREFIX=${wasi_resource_dir}
     EXCLUDE_FROM_ALL ON
     USES_TERMINAL_CONFIGURE ON
@@ -162,7 +165,6 @@ function(define_wasi_libc_sub target target_suffix lto)
       -DCMAKE_C_FLAGS=${extra_cflags}
       -DBUILTINS_LIB=${libcompiler_rt_a}
       -DUSE_WASM_COMPONENT_LD=OFF
-      -DBINDINGS_TARGET=OFF
       -DWASI_SDK_VERSION=${wasi_sdk_version}
     DEPENDS compiler-rt
     EXCLUDE_FROM_ALL ON
@@ -221,6 +223,17 @@ function(define_libcxx_sub target target_suffix extra_target_flags extra_libdir_
     --sysroot ${wasi_sysroot}
     -resource-dir ${wasi_resource_dir})
 
+  if (WASI_SDK_EXCEPTIONS)
+    # TODO: lots of builds fail with shared libraries and `-fPIC`. Looks like
+    # things are maybe changing in llvm/llvm-project#159143 but otherwise I'm at
+    # least not really sure what the state of shared libraries and exceptions
+    # are. For now shared libraries are disabled and supporting them is left for
+    # a future endeavor.
+    set(pic OFF)
+    set(runtimes "libunwind;${runtimes}")
+    list(APPEND extra_flags -fwasm-exceptions -mllvm -wasm-use-legacy-eh=false)
+  endif()
+
   set(extra_cflags_list ${CMAKE_C_FLAGS} ${extra_flags})
   list(JOIN extra_cflags_list " " extra_cflags)
   set(extra_cxxflags_list ${CMAKE_CXX_FLAGS} ${extra_flags})
@@ -244,14 +257,14 @@ function(define_libcxx_sub target target_suffix extra_target_flags extra_libdir_
       -DLLVM_COMPILER_CHECKED=ON
       -DLIBCXX_ENABLE_SHARED:BOOL=${pic}
       -DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY:BOOL=OFF
-      -DLIBCXX_ENABLE_EXCEPTIONS:BOOL=OFF
+      -DLIBCXX_ENABLE_EXCEPTIONS:BOOL=${WASI_SDK_EXCEPTIONS}
       -DLIBCXX_ENABLE_FILESYSTEM:BOOL=ON
       -DLIBCXX_ENABLE_ABI_LINKER_SCRIPT:BOOL=OFF
       -DLIBCXX_CXX_ABI=libcxxabi
       -DLIBCXX_CXX_ABI_INCLUDE_PATHS=${llvm_proj_dir}/libcxxabi/include
       -DLIBCXX_HAS_MUSL_LIBC:BOOL=ON
       -DLIBCXX_ABI_VERSION=2
-      -DLIBCXXABI_ENABLE_EXCEPTIONS:BOOL=OFF
+      -DLIBCXXABI_ENABLE_EXCEPTIONS:BOOL=${WASI_SDK_EXCEPTIONS}
       -DLIBCXXABI_ENABLE_SHARED:BOOL=${pic}
       -DLIBCXXABI_SILENT_TERMINATE:BOOL=ON
       -DLIBCXXABI_ENABLE_THREADS:BOOL=ON
@@ -260,12 +273,18 @@ function(define_libcxx_sub target target_suffix extra_target_flags extra_libdir_
       -DLIBCXXABI_BUILD_EXTERNAL_THREAD_LIBRARY:BOOL=OFF
       -DLIBCXXABI_HAS_WIN32_THREAD_API:BOOL=OFF
       -DLIBCXXABI_ENABLE_PIC:BOOL=${pic}
-      -DLIBCXXABI_USE_LLVM_UNWINDER:BOOL=OFF
+      -DLIBCXXABI_USE_LLVM_UNWINDER:BOOL=${WASI_SDK_EXCEPTIONS}
+      -DLIBUNWIND_ENABLE_SHARED:BOOL=${pic}
+      -DLIBUNWIND_ENABLE_THREADS:BOOL=ON
+      -DLIBUNWIND_USE_COMPILER_RT:BOOL=ON
+      -DLIBUNWIND_INCLUDE_TESTS:BOOL=OFF
       -DUNIX:BOOL=ON
       -DCMAKE_C_FLAGS=${extra_cflags}
+      -DCMAKE_ASM_FLAGS=${extra_cflags}
       -DCMAKE_CXX_FLAGS=${extra_cxxflags}
       -DLIBCXX_LIBDIR_SUFFIX=/${target}${extra_libdir_suffix}
       -DLIBCXXABI_LIBDIR_SUFFIX=/${target}${extra_libdir_suffix}
+      -DLIBUNWIND_LIBDIR_SUFFIX=/${target}${extra_libdir_suffix}
       -DLIBCXX_INCLUDE_TESTS=OFF
       -DLIBCXX_INCLUDE_BENCHMARKS=OFF
 
@@ -280,6 +299,9 @@ function(define_libcxx_sub target target_suffix extra_target_flags extra_libdir_
     USES_TERMINAL_CONFIGURE ON
     USES_TERMINAL_BUILD ON
     USES_TERMINAL_INSTALL ON
+    PATCH_COMMAND
+      ${CMAKE_COMMAND} -E chdir .. bash -c
+        "git apply ${CMAKE_SOURCE_DIR}/src/llvm-pr-168449.patch || git apply ${CMAKE_SOURCE_DIR}/src/llvm-pr-168449.patch -R --check"
   )
 endfunction()
 

cmake/wasi-sdk-toolchain.cmake

@@ -119,7 +119,7 @@ install(DIRECTORY ${wasi_tmp_install}/bin ${wasi_tmp_install}/lib ${wasi_tmp_ins
 # Build logic for `wasm-component-ld` installed from Rust code.
 set(wasm_component_ld_root ${CMAKE_CURRENT_BINARY_DIR}/wasm-component-ld)
 set(wasm_component_ld ${wasm_component_ld_root}/bin/wasm-component-ld${CMAKE_EXECUTABLE_SUFFIX})
-set(wasm_component_ld_version 0.5.20)
+set(wasm_component_ld_version 0.5.21)
 if(RUST_TARGET)
   set(rust_target_flag --target=${RUST_TARGET})
 endif()

src/llvm-pr-168449.patch

@@ -0,0 +1,28 @@
+diff --git a/libunwind/src/assembly.h b/libunwind/src/assembly.h
+index f8e83e138eff..c5097d25b0c6 100644
+--- a/libunwind/src/assembly.h
++++ b/libunwind/src/assembly.h
+@@ -249,6 +249,9 @@ aliasname:                                                                     \
+ #define WEAK_ALIAS(name, aliasname)
+ #define NO_EXEC_STACK_DIRECTIVE
+ 
++#elif defined(__wasm__)
++#define NO_EXEC_STACK_DIRECTIVE
++
+ // clang-format on
+ #else
+ 
+diff --git a/libunwind/src/config.h b/libunwind/src/config.h
+index deb5a4d4d73d..23c9f012cbcf 100644
+--- a/libunwind/src/config.h
++++ b/libunwind/src/config.h
+@@ -66,7 +66,8 @@
+   #define _LIBUNWIND_EXPORT
+   #define _LIBUNWIND_HIDDEN
+ #else
+-  #if !defined(__ELF__) && !defined(__MACH__) && !defined(_AIX)
++  #if !defined(__ELF__) && !defined(__MACH__) && !defined(_AIX) &&             \
++      !defined(__wasm__)
+     #define _LIBUNWIND_EXPORT __declspec(dllexport)
+     #define _LIBUNWIND_HIDDEN
+   #else

tests/CMakeLists.txt

@@ -67,7 +67,12 @@ function(add_testcase runwasi test)
 
       # Apply language-specific options and dependencies.
       if(test MATCHES "cc$")
-        target_compile_options(${target_name} PRIVATE -fno-exceptions)
+        if(WASI_SDK_EXCEPTIONS)
+          target_compile_options(${target_name} PRIVATE -fwasm-exceptions -mllvm -wasm-use-legacy-eh=false)
+          target_link_options(${target_name} PRIVATE -lunwind)
+        else()
+          target_compile_options(${target_name} PRIVATE -fno-exceptions)
+        endif()
         if(NOT WASI_SDK_TEST_HOST_TOOLCHAIN)
           add_dependencies(${target_name} libcxx-${target})
         endif()
@@ -84,11 +89,20 @@ function(add_testcase runwasi test)
       endif()
 
       if(runwasi)
+        set(runner ${runwasi})
+        if(${runner} MATCHES wasmtime)
+          if(target MATCHES threads)
+            set(runner "${runner} -Wshared-memory")
+          endif()
+          if(WASI_SDK_EXCEPTIONS)
+            set(runner "${runner} -Wexceptions")
+          endif()
+        endif()
         add_test(
           NAME test-${target_name}
           COMMAND
             bash ../testcase.sh
-            "${runwasi}"
+            ${runner}
             ${test}
             $<TARGET_FILE:${target_name}>
           WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})

tests/general/exceptions.cc

@@ -0,0 +1,17 @@
+#include <iostream>
+#include <stdlib.h>
+
+int main() {
+#ifdef __wasm_exception_handling__
+  try {
+    throw std::runtime_error("An error occurred");
+    abort();
+  } catch (const std::runtime_error& e) {
+    // ..
+    return 0;
+  }
+  abort();
+#else
+  return 0;
+#endif
+}

tests/testcase.sh

@@ -46,7 +46,7 @@ fi
 
 # Run the test, capturing stdout, stderr, and the exit status.
 exit_status=0
-"$runwasi" $env $dir "$wasm" $dirarg \
+$runwasi $env $dir "$wasm" $dirarg \
     < "$stdin" \
     > "$stdout_observed" \
     2> "$stderr_observed" \