[wasm2c] Add the very beginning of a wasm2c implementation and test harness

.gitignore

@@ -17,6 +17,7 @@ options-pinned.h
 # files related to building in-tree
 CMakeFiles
 *.cmake
+!src/tools/wasm2c/gen-wasm2c-templates.cmake
 /CMakeCache.txt
 /Makefile
 /*.ninja

.gitmodules

@@ -10,3 +10,9 @@
 [submodule "third_party/mimalloc"]
 	path = third_party/mimalloc
 	url = https://github.com/microsoft/mimalloc.git
+[submodule "third_party/simde"]
+	path = third_party/simde
+	url = https://github.com/simd-everywhere/simde
+[submodule "third_party/picosha2"]
+	path = third_party/picosha2
+	url = https://github.com/okdshin/PicoSHA2

CMakeLists.txt

@@ -412,8 +412,8 @@ else() # MSVC
   add_compile_flag("-Wno-unknown-warning-option")
   add_compile_flag("-Wswitch") # we explicitly expect this in the code
   add_compile_flag("-Wimplicit-fallthrough")
-  add_compile_flag("-Wnon-virtual-dtor")
-  add_compile_flag("-Wsuggest-override")
+  add_compile_flag("-Wnon-virtual-dtor" "CXX_ONLY")
+  add_compile_flag("-Wsuggest-override" "CXX_ONLY")
 
   if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
     # Google style requires this, so make sure we compile cleanly with it.

check.py

@@ -25,7 +25,15 @@
 from multiprocessing.pool import ThreadPool
 from pathlib import Path
 
-from scripts.test import binaryenjs, finalize, shared, support, wasm2js, wasm_opt
+from scripts.test import (
+    binaryenjs,
+    finalize,
+    shared,
+    support,
+    wasm2c,
+    wasm2js,
+    wasm_opt,
+)
 from scripts.test.shared import print_heading
 
 assert sys.version_info >= (3, 10), 'requires Python 3.10'
@@ -442,6 +450,7 @@ def wrapper(*args, **kwargs):
     'spec': run_spec_tests,
     'finalize': finalize.test_wasm_emscripten_finalize,
     'wasm2js': wasm2js.test_wasm2js,
+    'wasm2c-spec': wasm2c.test_wasm2c_spec,
     'validator': run_validator_tests,
     'example': run_example_tests,
     'unit': run_unittest,

scripts/test/shared.py

@@ -213,6 +213,7 @@ def is_exe(fpath):
 WASM_AS = [os.path.join(options.binaryen_bin, 'wasm-as')]
 WASM_DIS = [os.path.join(options.binaryen_bin, 'wasm-dis')]
 WASM2JS = [os.path.join(options.binaryen_bin, 'wasm2js')]
+WASM2C = [os.path.join(options.binaryen_bin, 'wasm2c')]
 WASM_CTOR_EVAL = [os.path.join(options.binaryen_bin, 'wasm-ctor-eval')]
 WASM_SHELL = [os.path.join(options.binaryen_bin, 'wasm-shell')]
 WASM_REDUCE = [os.path.join(options.binaryen_bin, 'wasm-reduce')]

scripts/test/wasm2c.py

@@ -0,0 +1,67 @@
+# Copyright 2026 WebAssembly Community Group participants
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pathlib
+
+from . import shared, support
+from .shared import print_heading
+
+spec_tests = [
+]
+
+
+def test_wasm2c_spec_output():
+    for t in shared.options.spec_tests:
+        test_path = pathlib.Path(t)
+        if test_path.name not in spec_tests:
+            continue
+
+        print('..', test_path.name)
+
+        is_fail_test = '.fail' in test_path.name
+
+        test_subdir = f'wasm2c_spec_{test_path.stem}'
+        test_subdir_path = pathlib.Path(test_subdir)
+        test_subdir_path.mkdir(exist_ok=True)
+
+        wasm2c_cmd = [shared.WASM2C[0], t, '-o', f'{test_subdir}/{test_path.stem}.c', '--allow-asserts']
+        support.run_command(wasm2c_cmd, expected_status=(1 if is_fail_test else 0))
+
+        c_sources = sorted(test_subdir_path.glob('*.c'))
+
+        wasm_rt_dir = pathlib.Path(shared.options.binaryen_root) / 'src' / 'tools' / 'wasm2c' / 'wasm-rt'
+        c_sources.append(wasm_rt_dir / 'wasm-rt-impl.c')
+        c_sources.append(wasm_rt_dir / 'wasm-rt-mem-impl.c')
+        c_sources.append(wasm_rt_dir / 'wasm-rt-exceptions-impl.c')
+
+        compile_cmd = [shared.NATIVECC, '-O2', '-std=c11', '-D_GNU_SOURCE', '-D_DEFAULT_SOURCE', '-I.', f"-I{wasm_rt_dir}"] + [str(s) for s in c_sources] + ['-o', f'{test_subdir}/spec_test_runner']
+
+        compile_cmd += ['-fno-optimize-sibling-calls', '-frounding-math']
+        if 'gcc' in shared.NATIVECC.lower():
+            compile_cmd.append('-fsignaling-nans')
+
+        compile_cmd.append('-lm')
+        compile_cmd.append('-lpthread')
+
+        support.run_command(compile_cmd)
+
+        # Run spec test runner binary and assert success
+        support.run_command([f'{test_subdir}/spec_test_runner'])
+
+
+def test_wasm2c_spec():
+    print_heading('checking wasm2c spec testcases...')
+    if shared.skip_if_on_windows('wasm2c-spec'):
+        return
+    test_wasm2c_spec_output()

src/tools/CMakeLists.txt

@@ -11,6 +11,7 @@ set(fuzzing_SOURCES
 binaryen_add_executable(wasm-opt "${fuzzing_SOURCES};wasm-opt.cpp")
 binaryen_add_executable(wasm-metadce wasm-metadce.cpp)
 binaryen_add_executable(wasm2js wasm2js.cpp)
+add_subdirectory(wasm2c)
 binaryen_add_executable(wasm-emscripten-finalize wasm-emscripten-finalize.cpp)
 binaryen_add_executable(wasm-as wasm-as.cpp)
 binaryen_add_executable(wasm-dis wasm-dis.cpp)

src/tools/wasm2c/CMakeLists.txt

@@ -0,0 +1,40 @@
+set(PREBUILT_DIR ${CMAKE_CURRENT_SOURCE_DIR}/prebuilt)
+set(WASM_RT_DIR ${CMAKE_CURRENT_SOURCE_DIR}/wasm-rt)
+
+set(WASM2C_TEMPLATE_SOURCES
+    ${PREBUILT_DIR}/wasm2c_header_top.cpp
+    ${PREBUILT_DIR}/wasm2c_header_bottom.cpp
+    ${PREBUILT_DIR}/wasm2c_source_includes.cpp
+    ${PREBUILT_DIR}/wasm2c_source_declarations.cpp
+    ${PREBUILT_DIR}/wasm2c_simd_source_declarations.cpp
+    ${PREBUILT_DIR}/wasm2c_atomicops_source_declarations.cpp
+    ${PREBUILT_DIR}/wasm2c_spec_top.cpp
+)
+
+binaryen_add_executable(wasm2c "wasm2c-builder.cpp;assertion-emitter.cpp;wasm2c.cpp;${WASM2C_TEMPLATE_SOURCES}")
+# TODO: https://github.com/WebAssembly/binaryen/issues/8775 - stop using picosha2
+target_include_directories(wasm2c PRIVATE ${PROJECT_SOURCE_DIR}/third_party/picosha2 ${PROJECT_SOURCE_DIR}/src/tools/wasm2c)
+
+set(WASM_RT_SOURCES
+  ${WASM_RT_DIR}/wasm-rt-exceptions-impl.c
+  ${WASM_RT_DIR}/wasm-rt-impl.c
+  ${WASM_RT_DIR}/wasm-rt-mem-impl.c
+)
+
+set(WASM_RT_INCLUDES
+  ${WASM_RT_DIR}/wasm-rt-exceptions.h
+  ${WASM_RT_DIR}/wasm-rt.h
+  ${WASM_RT_DIR}/wasm-rt-impl.h
+  ${WASM_RT_DIR}/wasm-rt-impl-tableops.inc
+  ${WASM_RT_DIR}/wasm-rt-mem-impl-helper.inc
+)
+
+set_source_files_properties(${WASM_RT_SOURCES}
+    PROPERTIES LANGUAGE C
+)
+
+set_source_files_properties(${WASM_RT_INCLUDES}
+    PROPERTIES LANGUAGE C
+)
+
+add_library(wasm-rt ${WASM_RT_SOURCES})