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Undefined symbol _emscripten_memcpy_js when linking rust code with -lc -Oz #22742

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Undefined symbol _emscripten_memcpy_js when linking rust code with -lc -Oz#22742

Description

@hoodmane
hoodmane
opened on Oct 15, 2024

You need rust and the emscripten target installed. rustup target add wasm32-unknown-emscripten installs the emscripten target if you use rustup.

echo "fn main(){}" > a.rs
rustc -Copt-level=z a.rs -o a.js --target=wasm32-unknown-emscripten

Fails with:

          error: undefined symbol: _emscripten_memcpy_js (referenced by root reference (e.g. compiled C/C++ code))
          warning: To disable errors for undefined symbols use `-sERROR_ON_UNDEFINED_SYMBOLS=0`
          warning: __emscripten_memcpy_js may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library
          Error: Aborting compilation due to previous errors
          emcc: error: '/home/rchatham/Documents/programming/emsdk/node/18.20.3_64bit/bin/node /home/rchatham/Documents/programming/emsdk/upstream/emscripten/src/compiler.mjs /tmp/tmpogw1glcz.json' failed (returned 1)

If we minimize the failing emcc link command, it looks like:

emcc -o a.js -Oz -lc \
a.a.<some-hash>-cgu.0.rcgu.o \
a.<some-hash>.rcgu.o \
.../lib/rustlib/wasm32-unknown-emscripten/lib/libstd-1d3ccab4f7990fa9.rlib \
.../lib/rustlib/wasm32-unknown-emscripten/lib/libpanic_abort-bb30bbb88530dc79.rlib \
.../lib/rustlib/wasm32-unknown-emscripten/lib/liballoc-6b694a8bc75de25c.rlib \
.../lib/rustlib/wasm32-unknown-emscripten/lib/libcore-99daaba8bfbbfe7e.rlib \

If I remove either -Oz or -lc then it succeeds. If I pass EMCC_DEBUG=1 and look at the contents of tmpogw1glcz.json it looks like:

Details

{
"ABORTING_MALLOC": true,
"ABORT_ON_WASM_EXCEPTIONS": false,
"AGGRESSIVE_VARIABLE_ELIMINATION": 0,
"ALIASING_FUNCTION_POINTERS": 0,
"ALLOW_BLOCKING_ON_MAIN_THREAD": true,
"ALLOW_MEMORY_GROWTH": false,
"ALLOW_TABLE_GROWTH": false,
"ALLOW_UNIMPLEMENTED_SYSCALLS": true,
"ALL_INCOMING_MODULE_JS_API": [
"ENVIRONMENT",
"GL_MAX_TEXTURE_IMAGE_UNITS",
"SDL_canPlayWithWebAudio",
"SDL_numSimultaneouslyQueuedBuffers",
"INITIAL_MEMORY",
"wasmMemory",
"arguments",
"buffer",
"canvas",
"doNotCaptureKeyboard",
"dynamicLibraries",
"elementPointerLock",
"extraStackTrace",
"forcedAspectRatio",
"instantiateWasm",
"keyboardListeningElement",
"freePreloadedMediaOnUse",
"loadSplitModule",
"locateFile",
"logReadFiles",
"mainScriptUrlOrBlob",
"mem",
"monitorRunDependencies",
"noExitRuntime",
"noInitialRun",
"onAbort",
"onCustomMessage",
"onExit",
"onFree",
"onFullScreen",
"onMalloc",
"onRealloc",
"onRuntimeInitialized",
"postMainLoop",
"postRun",
"preInit",
"preMainLoop",
"preRun",
"preinitializedWebGLContext",
"preloadPlugins",
"print",
"printErr",
"setStatus",
"statusMessage",
"stderr",
"stdin",
"stdout",
"thisProgram",
"wasm",
"wasmBinary",
"websocket",
"fetchSettings"
],
"ASAN_SHADOW_SIZE": -1,
"ASM_JS": 1,
"ASM_PRIMITIVE_VARS": [],
"ASSERTIONS": 0,
"ASYNCIFY": 0,
"ASYNCIFY_ADD": [],
"ASYNCIFY_ADVISE": false,
"ASYNCIFY_BLACKLIST": [],
"ASYNCIFY_DEBUG": 0,
"ASYNCIFY_EXPORTS": [],
"ASYNCIFY_IGNORE_INDIRECT": false,
"ASYNCIFY_IMPORTS": [],
"ASYNCIFY_IMPORTS_EXCEPT_JS_LIBS": [],
"ASYNCIFY_LAZY_LOAD_CODE": false,
"ASYNCIFY_ONLY": [],
"ASYNCIFY_PROPAGATE_ADD": true,
"ASYNCIFY_REMOVE": [],
"ASYNCIFY_STACK_SIZE": 4096,
"ASYNCIFY_WHITELIST": [],
"AUDIO_WORKLET": 0,
"AUDIO_WORKLET_FILE": "",
"AUTODEBUG": false,
"AUTOLOAD_DYLIBS": true,
"AUTO_ARCHIVE_INDEXES": 0,
"AUTO_JS_LIBRARIES": true,
"AUTO_NATIVE_LIBRARIES": true,
"BINARYEN": 1,
"BINARYEN_ASYNC_COMPILATION": true,
"BINARYEN_EXTRA_PASSES": "",
"BINARYEN_FEATURES": [
"--mvp-features",
"--enable-multivalue",
"--enable-mutable-globals",
"--enable-reference-types",
"--enable-sign-ext"
],
"BINARYEN_IGNORE_IMPLICIT_TRAPS": false,
"BINARYEN_MEM_MAX": 2147483648,
"BINARYEN_METHOD": "native-wasm",
"BINARYEN_PASSES": "",
"BINARYEN_SCRIPTS": "",
"BINARYEN_TRAP_MODE": -1,
"BOOTSTRAPPING_STRUCT_INFO": false,
"BUILD_AS_SHARED_LIB": 0,
"BUILD_AS_WORKER": false,
"BULK_MEMORY": false,
"CAN_ADDRESS_2GB": false,
"CASE_INSENSITIVE_FS": false,
"CHECK_NULL_WRITES": true,
"CLOSURE_WARNINGS": "quiet",
"DEAD_FUNCTIONS": [],
"DEBUG_LEVEL": 0,
"DECLARE_ASM_MODULE_EXPORTS": true,
"DEFAULT_LIBRARY_FUNCS_TO_INCLUDE": [
"$ExitStatus",
"$callRuntimeCallbacks",
"$getValue",
"$noExitRuntime",
"$setValue",
"$stackRestore",
"$stackSave",
"__cxa_find_matching_catch_2",
"__cxa_find_matching_catch_4",
"__resumeException",
"__syscall_getcwd",
"_abort_js",
"_emscripten_memcpy_js",
"emscripten_resize_heap",
"environ_get",
"environ_sizes_get",
"fd_write",
"llvm_eh_typeid_for",
"$exitJS",
"$handleException",
"$stringToUTF8OnStack",
"$getWasmTableEntry"
],
"DEFAULT_PTHREAD_STACK_SIZE": 0,
"DEFAULT_TO_CXX": true,
"DEMANGLE_SUPPORT": false,
"DETERMINISTIC": false,
"DISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR": true,
"DISABLE_EXCEPTION_CATCHING": 1,
"DISABLE_EXCEPTION_THROWING": false,
"DOUBLE_MODE": 0,
"DYLINK_DEBUG": 0,
"DYNAMIC_EXECUTION": 1,
"DYNCALLS": false,
"ELIMINATE_DUPLICATE_FUNCTIONS": 0,
"ELIMINATE_DUPLICATE_FUNCTIONS_DUMP_EQUIVALENT_FUNCTIONS": 0,
"ELIMINATE_DUPLICATE_FUNCTIONS_PASSES": 5,
"EMBIND": false,
"EMBIND_AOT": false,
"EMBIND_STD_STRING_IS_UTF8": true,
"EMITTING_JS": 1,
"EMIT_EMSCRIPTEN_LICENSE": false,
"EMIT_EMSCRIPTEN_METADATA": 0,
"EMIT_NAME_SECTION": false,
"EMIT_PRODUCERS_SECTION": false,
"EMIT_SYMBOL_MAP": false,
"EMIT_TSD": false,
"EMSCRIPTEN_TRACING": false,
"EMSCRIPTEN_VERSION": "3.1.68",
"EMULATE_FUNCTION_POINTER_CASTS": false,
"ENVIRONMENT": "web,webview,worker,node",
"ENVIRONMENT_MAY_BE_NODE": true,
"ENVIRONMENT_MAY_BE_SHELL": false,
"ENVIRONMENT_MAY_BE_WEB": true,
"ENVIRONMENT_MAY_BE_WEBVIEW": true,
"ENVIRONMENT_MAY_BE_WORKER": true,
"ERROR_ON_MISSING_LIBRARIES": 1,
"ERROR_ON_UNDEFINED_SYMBOLS": true,
"ERROR_ON_WASM_CHANGES_AFTER_LINK": false,
"EVAL_CTORS": 0,
"EXCEPTION_CATCHING_ALLOWED": [],
"EXCEPTION_CATCHING_WHITELIST": [],
"EXCEPTION_DEBUG": false,
"EXCEPTION_STACK_TRACES": false,
"EXIT_RUNTIME": false,
"EXPECT_MAIN": true,
"EXPORTED_FUNCTIONS": [
"_memory",
"___indirect_function_table",
"_main"
],
"EXPORTED_RUNTIME_METHODS": [
"HEAPF32",
"HEAPF64",
"HEAP_DATA_VIEW",
"HEAP8",
"HEAPU8",
"HEAP16",
"HEAPU16",
"HEAP32",
"HEAPU32",
"HEAP64",
"HEAPU64"
],
"EXPORT_ALL": false,
"EXPORT_BINDINGS": 0,
"EXPORT_ES6": false,
"EXPORT_EXCEPTION_HANDLING_HELPERS": false,
"EXPORT_FUNCTION_TABLES": 0,
"EXPORT_IF_DEFINED": [
"__start_em_asm",
"__stop_em_asm",
"__start_em_lib_deps",
"__stop_em_lib_deps",
"__start_em_js",
"__stop_em_js",
"main",
"__main_argc_argv"
],
"EXPORT_KEEPALIVE": true,
"EXPORT_NAME": "Module",
"EXTRA_EXPORTED_RUNTIME_METHODS": [],
"FAST_UNROLLED_MEMCPY_AND_MEMSET": 0,
"FETCH": false,
"FETCH_DEBUG": false,
"FETCH_SUPPORT_INDEXEDDB": true,
"FILESYSTEM": true,
"FINALIZE_ASM_JS": 0,
"FORCE_ALIGNED_MEMORY": 0,
"FORCE_FILESYSTEM": false,
"FS_DEBUG": false,
"FULL_ES2": false,
"FULL_ES3": false,
"FUNCTION_POINTER_ALIGNMENT": 2,
"GENERATE_DWARF": false,
"GENERATE_SOURCE_MAP": false,
"GLOBAL_BASE": 1024,
"GL_ASSERTIONS": false,
"GL_DEBUG": false,
"GL_DISABLE_HALF_FLOAT_EXTENSION_IF_BROKEN": false,
"GL_EMULATE_GLES_VERSION_STRING_FORMAT": true,
"GL_ENABLE_GET_PROC_ADDRESS": true,
"GL_EXPLICIT_UNIFORM_BINDING": false,
"GL_EXPLICIT_UNIFORM_LOCATION": false,
"GL_EXTENSIONS_IN_PREFIXED_FORMAT": true,
"GL_FFP_ONLY": false,
"GL_MAX_TEMP_BUFFER_SIZE": 2097152,
"GL_POOL_TEMP_BUFFERS": true,
"GL_PREINITIALIZED_CONTEXT": false,
"GL_SUPPORT_AUTOMATIC_ENABLE_EXTENSIONS": true,
"GL_SUPPORT_EXPLICIT_SWAP_CONTROL": false,
"GL_SUPPORT_SIMPLE_ENABLE_EXTENSIONS": true,
"GL_TESTING": false,
"GL_TRACK_ERRORS": true,
"GL_UNSAFE_OPTS": true,
"GL_WORKAROUND_SAFARI_GETCONTEXT_BUG": true,
"HAS_MAIN": true,
"HAVE_EM_ASM": false,
"HEADLESS": false,
"HEAP_BASE": 0,
"HTML5_SUPPORT_DEFERRING_USER_SENSITIVE_REQUESTS": true,
"IGNORE_CLOSURE_COMPILER_ERRORS": false,
"IGNORE_MISSING_MAIN": true,
"IMPORTED_MEMORY": false,
"INCLUDE_FULL_LIBRARY": false,
"INCLUDE_WEBGL1_FALLBACK": true,
"INCOMING_MODULE_JS_API": [
"ENVIRONMENT",
"GL_MAX_TEXTURE_IMAGE_UNITS",
"SDL_canPlayWithWebAudio",
"SDL_numSimultaneouslyQueuedBuffers",
"INITIAL_MEMORY",
"wasmMemory",
"arguments",
"buffer",
"canvas",
"doNotCaptureKeyboard",
"dynamicLibraries",
"elementPointerLock",
"extraStackTrace",
"forcedAspectRatio",
"instantiateWasm",
"keyboardListeningElement",
"freePreloadedMediaOnUse",
"loadSplitModule",
"locateFile",
"logReadFiles",
"mainScriptUrlOrBlob",
"mem",
"monitorRunDependencies",
"noExitRuntime",
"noInitialRun",
"onAbort",
"onCustomMessage",
"onExit",
"onFree",
"onFullScreen",
"onMalloc",
"onRealloc",
"onRuntimeInitialized",
"postMainLoop",
"postRun",
"preInit",
"preMainLoop",
"preRun",
"preinitializedWebGLContext",
"preloadPlugins",
"print",
"printErr",
"setStatus",
"statusMessage",
"stderr",
"stdin",
"stdout",
"thisProgram",
"wasm",
"wasmBinary",
"websocket"
],
"INITIAL_HEAP": 16777216,
"INITIAL_MEMORY": -1,
"INITIAL_TABLE": -1,
"INLINING_LIMIT": false,
"INVOKE_RUN": true,
"JSPI": 0,
"JSPI_EXPORTS": [],
"JSPI_IMPORTS": [],
"JS_LIBRARIES": [
"library_pthread_stub.js"
],
"JS_MATH": false,
"LEGACY_GL_EMULATION": false,
"LEGACY_RUNTIME": false,
"LEGACY_SETTINGS": [
"BINARYEN",
"TOTAL_STACK",
"BINARYEN_ASYNC_COMPILATION",
"UNALIGNED_MEMORY",
"FORCE_ALIGNED_MEMORY",
"PGO",
"QUANTUM_SIZE",
"FUNCTION_POINTER_ALIGNMENT",
"RESERVED_FUNCTION_POINTERS",
"BUILD_AS_SHARED_LIB",
"SAFE_SPLIT_MEMORY",
"SPLIT_MEMORY",
"BINARYEN_METHOD",
"BINARYEN_TRAP_MODE",
"PRECISE_I64_MATH",
"MEMFS_APPEND_TO_TYPED_ARRAYS",
"ERROR_ON_MISSING_LIBRARIES",
"EMITTING_JS",
"SKIP_STACK_IN_SMALL",
"SAFE_STACK",
"MEMORY_GROWTH_STEP",
"ELIMINATE_DUPLICATE_FUNCTIONS",
"ELIMINATE_DUPLICATE_FUNCTIONS_DUMP_EQUIVALENT_FUNCTIONS",
"ELIMINATE_DUPLICATE_FUNCTIONS_PASSES",
"WASM_OBJECT_FILES",
"TOTAL_MEMORY",
"WASM_MEM_MAX",
"BINARYEN_MEM_MAX",
"BINARYEN_PASSES",
"SWAPPABLE_ASM_MODULE",
"ASM_JS",
"FINALIZE_ASM_JS",
"ASYNCIFY_WHITELIST",
"ASYNCIFY_BLACKLIST",
"EXCEPTION_CATCHING_WHITELIST",
"SEPARATE_ASM",
"SEPARATE_ASM_MODULE_NAME",
"FAST_UNROLLED_MEMCPY_AND_MEMSET",
"DOUBLE_MODE",
"PRECISE_F32",
"ALIASING_FUNCTION_POINTERS",
"AGGRESSIVE_VARIABLE_ELIMINATION",
"SIMPLIFY_IFS",
"DEAD_FUNCTIONS",
"WASM_BACKEND",
"EXPORT_BINDINGS",
"RUNNING_JS_OPTS",
"EXPORT_FUNCTION_TABLES",
"BINARYEN_SCRIPTS",
"WARN_UNALIGNED",
"ASM_PRIMITIVE_VARS",
"WORKAROUND_IOS_9_RIGHT_SHIFT_BUG",
"RUNTIME_FUNCS_TO_IMPORT",
"LIBRARY_DEPS_TO_AUTOEXPORT",
"EMIT_EMSCRIPTEN_METADATA",
"SHELL_FILE",
"LLD_REPORT_UNDEFINED",
"MEM_INIT_METHOD",
"USE_PTHREADS",
"USES_DYNAMIC_ALLOC",
"REVERSE_DEPS",
"RUNTIME_LOGGING",
"MIN_EDGE_VERSION",
"MIN_IE_VERSION",
"WORKAROUND_OLD_WEBGL_UNIFORM_UPLOAD_IGNORED_OFFSET_BUG",
"AUTO_ARCHIVE_INDEXES"
],
"LEGACY_VM_SUPPORT": false,
"LEGALIZE_JS_FFI": true,
"LIBRARY_DEBUG": false,
"LIBRARY_DEPS_TO_AUTOEXPORT": [],
"LINKABLE": false,
"LINK_AS_CXX": true,
"LLD_REPORT_UNDEFINED": 1,
"LOAD_SOURCE_MAP": false,
"LTO": 0,
"LZ4": false,
"MAIN_MODULE": 0,
"MAIN_READS_PARAMS": true,
"MALLOC": "dlmalloc",
"MAXIMUM_MEMORY": 2147483648,
"MAX_WEBGL_VERSION": 1,
"MAYBE_CLOSURE_COMPILER": false,
"MAYBE_WASM2JS": false,
"MEMFS_APPEND_TO_TYPED_ARRAYS": 1,
"MEMORY64": 0,
"MEMORYPROFILER": false,
"MEMORY_GROWTH_GEOMETRIC_CAP": 100663296,
"MEMORY_GROWTH_GEOMETRIC_STEP": 0.2,
"MEMORY_GROWTH_LINEAR_STEP": -1,
"MEMORY_GROWTH_STEP": -1,
"MEM_INIT_METHOD": 0,
"MINIFICATION_MAP": "",
"MINIFY_HTML": true,
"MINIFY_WASM_EXPORT_NAMES": true,
"MINIFY_WASM_IMPORTED_MODULES": 1,
"MINIFY_WASM_IMPORTS_AND_EXPORTS": 1,
"MINIFY_WHITESPACE": true,
"MINIMAL_RUNTIME": 0,
"MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION": false,
"MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION": false,
"MIN_CHROME_VERSION": 85,
"MIN_EDGE_VERSION": 2147483647,
"MIN_FIREFOX_VERSION": 79,
"MIN_IE_VERSION": 2147483647,
"MIN_NODE_VERSION": 160000,
"MIN_SAFARI_VERSION": 140100,
"MIN_WEBGL_VERSION": 1,
"MODULARIZE": false,
"NODEJS_CATCH_EXIT": false,
"NODEJS_CATCH_REJECTION": 0,
"NODERAWFS": false,
"NODE_CODE_CACHING": false,
"OFFSCREENCANVASES_TO_PTHREAD": "#canvas",
"OFFSCREENCANVAS_SUPPORT": false,
"OFFSCREEN_FRAMEBUFFER": false,
"OFFSCREEN_FRAMEBUFFER_FORBID_VAO_PATH": false,
"OPENAL_DEBUG": false,
"OPT_LEVEL": 2,
"PGO": 0,
"POLYFILL": true,
"POLYFILL_OLD_MATH_FUNCTIONS": 0,
"POST_JS_FILES": [],
"PRECISE_F32": 0,
"PRECISE_I64_MATH": 1,
"PRE_JS_FILES": [],
"PRINTF_LONG_DOUBLE": false,
"PROXY_POSIX_SOCKETS": false,
"PROXY_TO_PTHREAD": false,
"PROXY_TO_WORKER": false,
"PROXY_TO_WORKER_FILENAME": "",
"PTHREADS": false,
"PTHREADS_DEBUG": false,
"PTHREADS_PROFILING": false,
"PTHREAD_POOL_DELAY_LOAD": false,
"PTHREAD_POOL_SIZE": 0,
"PTHREAD_POOL_SIZE_STRICT": 1,
"PURE_WASI": false,
"QUANTUM_SIZE": 4,
"RELOCATABLE": false,
"REQUIRED_EXPORTS": [
"_emscripten_stack_alloc",
"__get_temp_ret",
"__set_temp_ret",
"__wasm_call_ctors",
"emscripten_stack_get_current",
"_emscripten_stack_restore"
],
"RESERVED_FUNCTION_POINTERS": false,
"RETAIN_COMPILER_SETTINGS": false,
"REVERSE_DEPS": "auto",
"RUNNING_JS_OPTS": 0,
"RUNTIME_DEBUG": false,
"RUNTIME_FUNCS_TO_IMPORT": [],
"RUNTIME_LINKED_LIBS": [],
"RUNTIME_LOGGING": false,
"SAFE_HEAP": 0,
"SAFE_HEAP_LOG": false,
"SAFE_SPLIT_MEMORY": 0,
"SAFE_STACK": 0,
"SDL2_IMAGE_FORMATS": [],
"SDL2_MIXER_FORMATS": [
"ogg"
],
"SEPARATE_ASM": 0,
"SEPARATE_ASM_MODULE_NAME": "",
"SEPARATE_DWARF": false,
"SEPARATE_DWARF_URL": "",
"SHARED_MEMORY": false,
"SHELL_FILE": "",
"SHRINK_LEVEL": 2,
"SIDE_MODULE": 0,
"SIDE_MODULE_EXPORTS": [],
"SIGNATURE_CONVERSIONS": [],
"SIMPLIFY_IFS": 1,
"SINGLE_FILE": false,
"SKIP_STACK_IN_SMALL": 0,
"SMALL_XHR_CHUNKS": false,
"SOCKET_DEBUG": false,
"SOCKET_WEBRTC": false,
"SOURCE_MAP_BASE": "",
"SPLIT_MEMORY": 0,
"SPLIT_MODULE": false,
"STACK_FIRST": false,
"STACK_HIGH": 0,
"STACK_LOW": 0,
"STACK_OVERFLOW_CHECK": 0,
"STACK_SIZE": 65536,
"STANDALONE_WASM": false,
"STB_IMAGE": false,
"STRICT": false,
"STRICT_JS": false,
"SUPPORTS_GLOBALTHIS": true,
"SUPPORTS_PROMISE_ANY": true,
"SUPPORT_BASE64_EMBEDDING": false,
"SUPPORT_BIG_ENDIAN": false,
"SUPPORT_ERRNO": true,
"SUPPORT_LONGJMP": "emscripten",
"SWAPPABLE_ASM_MODULE": 0,
"SYSCALLS_REQUIRE_FILESYSTEM": true,
"SYSCALL_DEBUG": false,
"TABLE_BASE": 1,
"TARGET_BASENAME": "a",
"TARGET_JS_NAME": "a.js",
"TEXTDECODER": 1,
"TOTAL_MEMORY": -1,
"TOTAL_STACK": 65536,
"TRACE_WEBGL_CALLS": false,
"TRANSPILE": false,
"TRUSTED_TYPES": false,
"UBSAN_RUNTIME": 0,
"UNALIGNED_MEMORY": 0,
"USER_EXPORTS": [],
"USES_DYNAMIC_ALLOC": 1,
"USE_ASAN": false,
"USE_BOOST_HEADERS": false,
"USE_BULLET": false,
"USE_BZIP2": false,
"USE_CLOSURE_COMPILER": false,
"USE_COCOS2D": 0,
"USE_ES6_IMPORT_META": true,
"USE_FREETYPE": false,
"USE_GIFLIB": false,
"USE_GLFW": 0,
"USE_HARFBUZZ": false,
"USE_ICU": false,
"USE_LIBJPEG": false,
"USE_LIBPNG": false,
"USE_LSAN": false,
"USE_MODPLUG": false,
"USE_MPG123": false,
"USE_OFFSET_CONVERTER": false,
"USE_OGG": false,
"USE_PTHREADS": 0,
"USE_READY_PROMISE": true,
"USE_REGAL": false,
"USE_RTTI": true,
"USE_SDL": 0,
"USE_SDL_GFX": 0,
"USE_SDL_IMAGE": 1,
"USE_SDL_MIXER": 1,
"USE_SDL_NET": 1,
"USE_SDL_TTF": 1,
"USE_SQLITE3": false,
"USE_VORBIS": false,
"USE_WEBGL2": false,
"USE_WEBGPU": false,
"USE_ZLIB": false,
"VERBOSE": false,
"WARN_DEPRECATED": true,
"WARN_ON_UNDEFINED_SYMBOLS": true,
"WARN_UNALIGNED": 0,
"WASI_MODULE_NAME": "wasi_snapshot_preview1",
"WASM": 1,
"WASM2JS": false,
"WASMFS": false,
"WASM_ASYNC_COMPILATION": true,
"WASM_BACKEND": -1,
"WASM_BIGINT": false,
"WASM_BINARY_FILE": "a.wasm",
"WASM_EXCEPTIONS": false,
"WASM_EXNREF": false,
"WASM_EXPORTS": [
"memory",
"__wasm_call_ctors",
"main",
"__indirect_function_table",
"malloc",
"htonl",
"htons",
"ntohs",
"_emscripten_tempret_set",
"_emscripten_stack_restore",
"_emscripten_stack_alloc",
"emscripten_stack_get_current",
"__cxa_can_catch"
],
"WASM_GLOBAL_EXPORTS": [],
"WASM_MEM_MAX": 2147483648,
"WASM_OBJECT_FILES": 0,
"WASM_WORKERS": 0,
"WASM_WORKER_FILE": "",
"WEAK_IMPORTS": [],
"WEBAUDIO_DEBUG": 0,
"WEBGL2_BACKWARDS_COMPATIBILITY_EMULATION": false,
"WEBGL_USE_GARBAGE_FREE_APIS": false,
"WEBSOCKET_DEBUG": false,
"WEBSOCKET_SUBPROTOCOL": "binary",
"WEBSOCKET_URL": "ws:#",
"WORKAROUND_IOS_9_RIGHT_SHIFT_BUG": 0,
"WORKAROUND_OLD_WEBGL_UNIFORM_UPLOAD_IGNORED_OFFSET_BUG": 0
}

If I delete _emscripten_memcpy_js from DEFAULT_LIBRARY_FUNCS_TO_INCLUDE then compiler.mjs succeeds.

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.68 (ceee49d2ecdab36a3feb85a684f8e5a453dde910)
clang version 20.0.0git (https:/github.com/llvm/llvm-project 5cc64bf60bc04b9315de3c679eb753de4d554a8a)
Target: wasm32-unknown-emscripten
Thread model: posix

Activity

  1. sbc100 commented on Oct 15, 2024

    @sbc100
    sbc100
    on Oct 15, 2024
    Collaborator

    _emscripten_memcpy_js is just a normal JS library function. I lives here:

    emscripten/src/library.js

    Lines 409 to 439 in 1dfe990

    // In -Oz builds, we replace memcpy() altogether with a non-unrolled wasm
    // variant, so we should never emit _emscripten_memcpy_js() in the build.
    // In STANDALONE_WASM we avoid the _emscripten_memcpy_js dependency so keep
    // the wasm file standalone.
    // In BULK_MEMORY mode we include native versions of these functions based
    // on memory.fill and memory.copy.
    // In MAIN_MODULE=1 or EMCC_FORCE_STDLIBS mode all of libc is force included
    // so we cannot override parts of it, and therefore cannot use libc_optz.
    #if (SHRINK_LEVEL < 2 || LINKABLE || process.env.EMCC_FORCE_STDLIBS) && !STANDALONE_WASM && !BULK_MEMORY
    #if MIN_CHROME_VERSION < 45 || MIN_FIREFOX_VERSION < 34 || MIN_SAFARI_VERSION < 100101
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/copyWithin lists browsers that support TypedArray.prototype.copyWithin, but it
    // has outdated information for Safari, saying it would not support it.
    // https://github.com/WebKit/webkit/commit/24a800eea4d82d6d595cdfec69d0f68e733b5c52#diff-c484911d8df319ba75fce0d8e7296333R1 suggests support was added on Aug 28, 2015.
    // Manual testing suggests:
    // Safari/601.1 Version/9.0 on iPhone 4s with iOS 9.3.6 (released September 30, 2015) does not support copyWithin.
    // but the following systems do:
    // AppleWebKit/602.2.14 Safari/602.1 Version/10.0 Mobile/14B100 iPhone OS 10_1_1 on iPhone 5s with iOS 10.1.1 (released October 31, 2016)
    // AppleWebKit/603.3.8 Safari/602.1 Version/10.0 on iPhone 5 with iOS 10.3.4 (released July 22, 2019)
    // AppleWebKit/605.1.15 iPhone OS 12_3_1 Version/12.1.1 Safari/604.1 on iPhone SE with iOS 12.3.1
    // AppleWebKit/605.1.15 Safari/604.1 Version/13.0.4 iPhone OS 13_3 on iPhone 6s with iOS 13.3
    // AppleWebKit/605.1.15 Version/13.0.3 Intel Mac OS X 10_15_1 on Safari 13.0.3 (15608.3.10.1.4) on macOS Catalina 10.15.1
    // Hence the support status of .copyWithin() for Safari version range [10.0.0, 10.1.0] is unknown.
    _emscripten_memcpy_js: `= Uint8Array.prototype.copyWithin
    ? (dest, src, num) => HEAPU8.copyWithin(dest, src, src + num)
    : (dest, src, num) => HEAPU8.set(HEAPU8.subarray(src, src+num), dest)`,
    #else
    _emscripten_memcpy_js: (dest, src, num) => HEAPU8.copyWithin(dest, src, src + num),
    #endif
    #endif

    Does your version of library JS also contains this symbol?

  2. hoodmane commented on Oct 16, 2024

    @hoodmane
    hoodmane
    on Oct 16, 2024
    CollaboratorAuthor

    Yeah library.js has _emscripten_memcpy_js. I am using stock emscripten 3.1.68 installed with emsdk. The following is a full reproduction:

    git clone https://github.com/emscripten-core/emsdk.git
./emsdk/emsdk install 3.1.68
./emsdk/emsdk activate 3.1.68
source ./emsdk/emsdk_env.sh
# install rustup
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
source $HOME/.cargo/env
rustup target add wasm32-unknown-emscripten
echo "fn main(){}" > a.rs
rustc -Copt-level=z a.rs -o a.js --target=wasm32-unknown-emscripten

  3. hoodmane commented on Oct 16, 2024

    @hoodmane
    hoodmane
    on Oct 16, 2024
    CollaboratorAuthor

    I've attached the output from --reproduce=repro.tar
    repro.tar.gz

  4. hoodmane commented on Oct 16, 2024

    @hoodmane
    hoodmane
    on Oct 16, 2024
    CollaboratorAuthor

    This also happens with -lc -sWASM_BIGINT.

  5. hoodmane
    added a commit that references this issue on Oct 18, 2024

    Drop explicitly passed -lc unless -nodefaultlibs or similar is passed

    3414463
  6. hoodmane
    added a commit that references this issue on Nov 1, 2024

    Don't pass -lc to Emscripten, it breaks

    66e3665
  7. tgross35
    added a commit that references this issue on Nov 6, 2024

    Don't pass -lc to Emscripten, it breaks

    31d430b

  8. hoodmane commented on Jan 14, 2025

    @hoodmane
    hoodmane
    on Jan 14, 2025
    CollaboratorAuthor

    This was resolved by rust-lang/libc#4002. Or not exactly resolved but worked around.

  9. hoodmane
    closed this as completedon Jan 14, 2025
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