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Merged
sbc100 merged 1 commit into from
May 16, 2026
Merged

Prefer standard clang -m64 flag over -sMEMORY64 #26963

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2 changes: 1 addition & 1 deletion cmake/Modules/Platform/Emscripten.cmake
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Expand Up @@ -219,7 +219,7 @@ endif()
list(APPEND CMAKE_FIND_ROOT_PATH "${EMSCRIPTEN_SYSROOT}")
list(APPEND CMAKE_SYSTEM_PREFIX_PATH /)

if (${CMAKE_C_FLAGS} MATCHES "MEMORY64")
if (${CMAKE_C_FLAGS} MATCHES "MEMORY64|-m64|--target=wasm64")
set(CMAKE_LIBRARY_ARCHITECTURE "wasm64-emscripten")
set(CMAKE_SIZEOF_VOID_P 8)
set(CMAKE_C_SIZEOF_DATA_PTR 8)
Expand Down
2 changes: 2 additions & 0 deletions site/source/docs/tools_reference/settings_reference.rst
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Expand Up @@ -311,6 +311,8 @@ The "architecture" to compile for. 0 means the default wasm32, 1 is
the full end-to-end wasm64 mode, and 2 is wasm64 for clang/lld but lowered to
wasm32 in Binaryen (such that it can run on wasm32 engines, while internally
using i64 pointers).
Nowadays we recommend using the more standard `-m64` or `--target=wasm64`
flags, which do the same thing.
Assumes WASM_BIGINT.

.. note:: Applicable during both linking and compilation
Expand Down
2 changes: 2 additions & 0 deletions src/settings.js
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Expand Up @@ -256,6 +256,8 @@ var MEMORY_GROWTH_LINEAR_STEP = -1;
// the full end-to-end wasm64 mode, and 2 is wasm64 for clang/lld but lowered to
// wasm32 in Binaryen (such that it can run on wasm32 engines, while internally
// using i64 pointers).
// Nowadays we recommend using the more standard `-m64` or `--target=wasm64`
// flags, which do the same thing.
// Assumes WASM_BIGINT.
// [compile+link]
var MEMORY64 = 0;
Expand Down
4 changes: 2 additions & 2 deletions test/common.py
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Expand Up @@ -434,7 +434,7 @@ def is_browser_test(self):
return False

def is_wasm64(self):
return self.get_setting('MEMORY64')
return '-m64' in self.cflags

def is_4gb(self):
return self.get_setting('INITIAL_MEMORY') == '4200mb'
Expand Down Expand Up @@ -618,7 +618,7 @@ def require_jspi(self):

def require_wasm2js(self):
if self.is_wasm64():
self.skipTest('wasm2js is not compatible with MEMORY64')
self.skipTest('wasm2js is not compatible with wasm64')
if self.is_2gb() or self.is_4gb():
self.skipTest('wasm2js does not support over 2gb of memory')
if self.get_setting('WASM_ESM_INTEGRATION'):
Expand Down
4 changes: 2 additions & 2 deletions test/decorators.py
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Expand Up @@ -417,7 +417,7 @@ def metafunc(self, with_wasm64, *args, **kwargs):
print('parameterize:wasm64=%s' % with_wasm64)
if with_wasm64:
self.require_wasm64()
self.set_setting('MEMORY64')
self.cflags += ['-m64']
return func(self, *args, **kwargs)

parameterize(metafunc, {'': (False,),
Expand Down Expand Up @@ -459,7 +459,7 @@ def metafunc(self, with_wasm2js, *args, **kwargs):


def can_do_standalone(self, impure=False):
# Pure standalone engines don't support MEMORY64 yet. Even with MEMORY64=2 (lowered)
# Pure standalone engines don't support wasm64 yet. Even with MEMORY64=2 (lowered)
# the WASI APIs that take pointer values don't have 64-bit variants yet.
if not impure:
if self.is_wasm64():
Expand Down
18 changes: 9 additions & 9 deletions test/test_benchmark.py
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Expand Up @@ -390,9 +390,9 @@ def get_output_files(self):
'v8': EmscriptenBenchmarker('v8', aot_v8),
'v8-lto': EmscriptenBenchmarker('v8-lto', aot_v8, ['-flto']),
'v8-ctors': EmscriptenBenchmarker('v8-ctors', aot_v8, ['-sEVAL_CTORS']),
'v8-64': EmscriptenBenchmarker('v8-64', aot_v8, ['-sMEMORY64=2']),
'v8-64': EmscriptenBenchmarker('v8-64', aot_v8, ['-m64']),
'node': EmscriptenBenchmarker('node', config.NODE_JS_TEST),
'node-64': EmscriptenBenchmarker('node-64', config.NODE_JS_TEST, ['-sMEMORY64=2']),
'node-64': EmscriptenBenchmarker('node-64', config.NODE_JS_TEST, ['-m64']),
'cherp-v8': CheerpBenchmarker('cheerp-v8-wasm', aot_v8),
# TODO: ensure no baseline compiler is used, see v8
'sm': EmscriptenBenchmarker('sm', config.SPIDERMONKEY_ENGINE),
Expand Down Expand Up @@ -1037,10 +1037,10 @@ def lua(self, benchmark, expected, output_parser=None):
copy_asset(f'third_party/lua/{benchmark}.lua')

def lib_builder(name, native, env_init):
# Inject -sMEMORY64 into node-64 benchmarking runs.
# Inject -m64 into node-64 benchmarking runs.
env_init['MYCFLAGS'] = env_init.get('CFLAGS', '')
if '-sMEMORY64' in env_init['MYCFLAGS']:
env_init['MYLDFLAGS'] = '-sMEMORY64'
if '-m64' in env_init['MYCFLAGS']:
env_init['MYLDFLAGS'] = '-m64'

# We force recomputation for the native benchmarker because this benchmark
# uses native_exec=True, so we need to copy the native executable
Expand Down Expand Up @@ -1169,9 +1169,9 @@ def test_zzz_poppler(self):
''' % DEFAULT_ARG)

def lib_builder(name, native, env_init): # noqa
if '-sMEMORY64' in env_init.get('CFLAGS', ''):
env_init['CPPFLAGS'] = '-sMEMORY64'
env_init['LDFLAGS'] = '-sMEMORY64'
if '-m64' in env_init.get('CFLAGS', ''):
env_init['CPPFLAGS'] = '-m64'
env_init['LDFLAGS'] = '-m64'
return self.get_poppler_library(env_init=env_init)

self.do_benchmark('poppler', '', 'hashed printout',
Expand All @@ -1182,6 +1182,6 @@ def lib_builder(name, native, env_init): # noqa
'-sERROR_ON_UNDEFINED_SYMBOLS=0',
'-sMINIMAL_RUNTIME=0'], # not minimal because of files
lib_builder=lib_builder,
# TODO: Fix poppler native and freetype MEMORY64 builds to be able
# TODO: Fix poppler native and freetype wasm64 builds to be able
# to remove these skips
skip_benchmarkers=['clang', 'gcc', 'v8-64', 'node-64'])
6 changes: 3 additions & 3 deletions test/test_browser.py
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Expand Up @@ -5685,14 +5685,14 @@ def test_shell_minimal(self, args):
class browser64(browser):
def setUp(self):
super().setUp()
self.set_setting('MEMORY64')
self.cflags += ['-m64']
self.require_wasm64()


class browser64_4gb(browser):
def setUp(self):
super().setUp()
self.set_setting('MEMORY64')
self.cflags += ['-m64']
self.set_setting('INITIAL_MEMORY', '4200mb')
self.set_setting('GLOBAL_BASE', '4gb')
# Without this we get a warning about GLOBAL_BASE being ignored when used with SIDE_MODULE
Expand All @@ -5703,7 +5703,7 @@ def setUp(self):
class browser64_2gb(browser):
def setUp(self):
super().setUp()
self.set_setting('MEMORY64')
self.cflags += ['-m64']
self.set_setting('INITIAL_MEMORY', '2200mb')
self.set_setting('GLOBAL_BASE', '2gb')
# Without this we get a warning about GLOBAL_BASE being ignored when used with SIDE_MODULE
Expand Down
2 changes: 1 addition & 1 deletion test/test_codesize.py
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Expand Up @@ -309,7 +309,7 @@ def strip_numeric_suffixes(funcname):
'Os_mr': (['-Os', '-sMINIMAL_RUNTIME'],),
# EVAL_CTORS also removes the __wasm_call_ctors function
'Oz-ctors': (['-Oz', '-sEVAL_CTORS'],),
'64': (['-Oz', '-sMEMORY64'],),
'64': (['-Oz', '-m64'],),
# WasmFS should not be fully linked into a minimal program.
'wasmfs': (['-Oz', '-sWASMFS'],),
'esm': (['-Oz', '-sEXPORT_ES6'],),
Expand Down
13 changes: 5 additions & 8 deletions test/test_core.py
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Expand Up @@ -9921,18 +9921,15 @@ def setUp(self):
core_2gb = make_run('core_2gb', cflags=['--profiling-funcs'],
settings={'INITIAL_MEMORY': '2200mb', 'GLOBAL_BASE': '2gb'})

# MEMORY64=1
wasm64 = make_run('wasm64', cflags=['--profiling-funcs'],
settings={'MEMORY64': 1}, require_wasm64=True)
wasm64_O2 = make_run('wasm64_O2', cflags=['-O2'],
settings={'MEMORY64': 1}, require_wasm64=True)
wasm64 = make_run('wasm64', cflags=['--profiling-funcs', '-m64'], require_wasm64=True)
wasm64_O2 = make_run('wasm64_O2', cflags=['-O2', '-m64'], require_wasm64=True)
# Run the wasm64 tests with all memory offsets > 4gb. Be careful running this test
# suite with any kind of parallelism.
wasm64_4gb = make_run('wasm64_4gb', cflags=['--profiling-funcs'],
settings={'MEMORY64': 1, 'INITIAL_MEMORY': '4200mb', 'GLOBAL_BASE': '4gb'},
wasm64_4gb = make_run('wasm64_4gb', cflags=['-m64', '--profiling-funcs'],
settings={'INITIAL_MEMORY': '4200mb', 'GLOBAL_BASE': '4gb'},
require_wasm64=True)
# MEMORY64=2, or "lowered"
wasm64l = make_run('wasm64l', cflags=['-O1', '--profiling-funcs'],
wasm64l = make_run('wasm64l', cflags=['-m64', '-O1', '--profiling-funcs'],
settings={'MEMORY64': 2})
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@kripken kripken May 15, 2026

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Why pass both -m64 and -MEMORY64=2?

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@sbc100 sbc100 May 16, 2026

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No reason. But its only not harmful.


lto0 = make_run('lto0', cflags=['-flto', '-O0'])
Expand Down
4 changes: 2 additions & 2 deletions test/test_interactive.py
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Expand Up @@ -389,14 +389,14 @@ def test_html_source_map(self):
class interactive64(interactive):
def setUp(self):
super().setUp()
self.set_setting('MEMORY64')
self.cflags += ['-m64']
self.require_wasm64()


class interactive64_4gb(interactive):
def setUp(self):
super().setUp()
self.set_setting('MEMORY64')
self.cflags += ['-m64']
self.set_setting('INITIAL_MEMORY', '4200mb')
self.set_setting('GLOBAL_BASE', '4gb')
self.require_wasm64()
Expand Down
44 changes: 24 additions & 20 deletions test/test_other.py
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Expand Up @@ -530,10 +530,13 @@ def test_dumpmachine(self):
output = self.run_process([EMCC, '--print-target-triple'], stdout=PIPE, stderr=PIPE).stdout
self.assertContained('wasm32-unknown-emscripten', output)

# Test that -sMEMORY64 triggers the wasm64 triple
# Test that -m64 / -sMEMORY64 triggers the wasm64 triple
output = self.run_process([EMCC, '-sMEMORY64', '-dumpmachine'], stdout=PIPE, stderr=PIPE).stdout
self.assertContained('wasm64-unknown-emscripten', output)

output = self.run_process([EMCC, '-m64', '-dumpmachine'], stdout=PIPE, stderr=PIPE).stdout
self.assertContained('wasm64-unknown-emscripten', output)

@parameterized({
'c': [EMCC, '.c'],
'cxx': [EMXX, '.cpp'],
Expand Down Expand Up @@ -703,7 +706,7 @@ def test_emcc_cflags(self):
@parameterized({
'': [[]],
'lto': [['-flto']],
'wasm64': [['-sMEMORY64']],
'wasm64': [['-m64']],
})
def test_print_search_dirs(self, args):
output = self.run_process([EMCC, '-print-search-dirs'] + args, stdout=PIPE).stdout
Expand All @@ -715,22 +718,22 @@ def test_print_search_dirs(self, args):
libpath = libpath.split(os.pathsep)
libpath = [Path(p) for p in libpath]
settings.LTO = '-flto' in args
settings.MEMORY64 = int('-sMEMORY64' in args)
settings.MEMORY64 = int('-m64' in args)
expected = cache.get_lib_dir(absolute=True)
self.assertIn(expected, libpath)

@crossplatform
@parameterized({
'': [[]],
'lto': [['-flto']],
'wasm64': [['-sMEMORY64']],
'wasm64': [['-m64']],
})
def test_print_libgcc_file_name(self, args):
output = self.run_process([EMCC, '-print-libgcc-file-name'] + args, stdout=PIPE).stdout
output2 = self.run_process([EMCC, '--print-libgcc-file-name'] + args, stdout=PIPE).stdout
self.assertEqual(output, output2)
settings.LTO = '-flto' in args
settings.MEMORY64 = int('-sMEMORY64' in args)
settings.MEMORY64 = int('-m64' in args)
libdir = cache.get_lib_dir(absolute=True)
expected = os.path.join(libdir, 'libcompiler_rt.a')
self.assertEqual(output.strip(), expected)
Expand All @@ -757,7 +760,7 @@ def test_print_prog_name(self):
@parameterized({
'': [[]],
'lto': [['-flto']],
'wasm64': [['-sMEMORY64']],
'wasm64': [['-m64']],
})
def test_print_file_name(self, args):
# make sure the corresponding version of libc exists in the cache
Expand All @@ -767,7 +770,7 @@ def test_print_file_name(self, args):
self.assertEqual(output, output2)
filename = Path(output)
settings.LTO = '-flto' in args
settings.MEMORY64 = int('-sMEMORY64' in args)
settings.MEMORY64 = int('-m64' in args)
self.assertContained(cache.get_lib_name('libc.a'), str(filename))

def test_emar_em_config_flag(self):
Expand Down Expand Up @@ -1085,17 +1088,17 @@ def test_pkg_config_ports(self):

@parameterized({
'': [None],
'wasm64': ['-sMEMORY64'],
'wasm64': ['-m64'],
'pthreads': ['-pthread'],
})
def test_cmake_check_type_size(self, cflag):
if cflag == '-sMEMORY64':
if cflag == '-m64':
self.require_wasm64()
cmd = [EMCMAKE, 'cmake', test_file('cmake/check_type_size')]
if cflag:
cmd += [f'-DCMAKE_CXX_FLAGS={cflag}', f'-DCMAKE_C_FLAGS={cflag}']
output = self.run_process(cmd, stdout=PIPE).stdout
if cflag == '-sMEMORY64':
if cflag == '-m64':
self.assertContained('CMAKE_SIZEOF_VOID_P -> 8', output)
else:
self.assertContained('CMAKE_SIZEOF_VOID_P -> 4', output)
Expand Down Expand Up @@ -3445,7 +3448,7 @@ def test_embind_subclass_pointer(self):
'no_utf8': ['-sEMBIND_STD_STRING_IS_UTF8=0'],
'no_dynamic': ['-sDYNAMIC_EXECUTION=0'],
'aot_js': ['-sDYNAMIC_EXECUTION=0', '-sEMBIND_AOT', '-DSKIP_UNBOUND_TYPES'],
'wasm64': ['-sMEMORY64'],
'wasm64': ['-m64'],
'2gb': ['-sINITIAL_MEMORY=2200mb', '-sGLOBAL_BASE=2gb'],
})
@parameterized({
Expand All @@ -3468,7 +3471,7 @@ def test_embind(self, *extra_args):
#
# By default all of them are run. If you are debugging and want to run just a subset of the
# JS tests you can use `EMBIND_TESTS=myregex` to run just the matching tests.
if '-sMEMORY64' in extra_args:
if '-m64' in extra_args:
self.require_wasm64()
self.cflags += [
'--no-entry',
Expand Down Expand Up @@ -3657,7 +3660,7 @@ def test_embind_tsgen_end_to_end(self, opts, tsc_opts):
'4': [['-fsanitize=undefined', '-gsource-map'], 'embind_tsgen_ignore_3.d.ts'],
'5': [['-sASYNCIFY'], 'embind_tsgen_ignore_3.d.ts'],
'6': [['-sENVIRONMENT=worker', '-lworkerfs.js'], 'embind_tsgen.d.ts'],
'7': [['-sMEMORY64=1', '-gsource-map'], 'embind_tsgen_ignore_7.d.ts'],
'7': [['-m64', '-gsource-map'], 'embind_tsgen_ignore_7.d.ts'],
})
def test_embind_tsgen_ignore(self, extra_args, expected_ts_file):
create_file('fail.js', 'assert(false);')
Expand Down Expand Up @@ -3737,7 +3740,7 @@ def test_embind_tsgen_bigint(self):
def test_embind_tsgen_wasm64(self, args):
# Check that when wasm64 is enabled longs & unsigned longs are mapped to bigint in the generated TS bindings
self.run_process([EMXX, test_file('other/embind_tsgen_wasm64.cpp'),
'-lembind', '--emit-tsd', 'embind_tsgen_wasm64.d.ts', '-sMEMORY64'] +
'-lembind', '--emit-tsd', 'embind_tsgen_wasm64.d.ts', '-m64'] +
args +
self.get_cflags())
self.assertFileContents(test_file('other/embind_tsgen_wasm64.d.ts'), read_file('embind_tsgen_wasm64.d.ts'))
Expand Down Expand Up @@ -6590,7 +6593,7 @@ def test_failing_growth_wasm64(self):
}
}
''')
self.do_runf('test.c', 'done\n', cflags=['-sGLOBAL_BASE=2Gb', '-sTOTAL_MEMORY=4Gb', '-sMAXIMUM_MEMORY=5Gb', '-sALLOW_MEMORY_GROWTH', '-sMEMORY64'])
self.do_runf('test.c', 'done\n', cflags=['-sGLOBAL_BASE=2Gb', '-sTOTAL_MEMORY=4Gb', '-sMAXIMUM_MEMORY=5Gb', '-sALLOW_MEMORY_GROWTH', '-m64'])

def test_libcxx_minimal(self):
create_file('vector.cpp', r'''
Expand Down Expand Up @@ -10055,7 +10058,7 @@ def test_wasm_producers_section(self, args):
# in some modes we run wasm-emscripten-finalize, which normally strips the
# features section for us, so add testing for those
'nobigint': (['-sWASM_BIGINT=0'],),
'wasm64': (['-sMEMORY64'],),
'wasm64': (['-m64'],),
})
def test_wasm_features_section(self, args):
# The features section should never be in our output, when we optimize.
Expand Down Expand Up @@ -13567,7 +13570,7 @@ def test_extended_const(self):
# Test that extended-const expressions are used in the data segments.
self.assertContained(r'\(data (\$\S+ )?\(offset \(i32.add\s+\(global.get \$\S+\)\s+\(i32.const \d+\)', wat, regex=True)

# Smoketest for MEMORY64 setting. Most of the testing of MEMORY64 is by way of the wasm64
# Smoketest for wasm64. Most of the testing of wasm64 is by way of the wasm64
# variant of the core test suite.
@parameterized({
'O0': (['-O0'],),
Expand All @@ -13577,8 +13580,8 @@ def test_extended_const(self):
'Oz': (['-Oz'],),
})
@requires_wasm64
def test_memory64(self, args):
self.do_run_in_out_file_test('core/test_hello_argc.c', args=['hello', 'world'], cflags=['-sMEMORY64'] + args)
def test_wasm64(self, args):
self.do_run_in_out_file_test('core/test_hello_argc.c', args=['hello', 'world'], cflags=['-m64'] + args)

# Verfy that MAIN_MODULE=1 (which includes all symbols from all libraries)
# works with -sPROXY_POSIX_SOCKETS and -Oz, both of which affect linking of
Expand Down Expand Up @@ -14379,6 +14382,7 @@ def is_64(path):
self.assertFalse(is_64('hello_world.wasm'))

self.assert_fail([EMCC, test_file('hello_world.c'), '-target', 'wasm32', '-sMEMORY64'], 'emcc: error: wasm32 target is not compatible with -sMEMORY64')
self.assert_fail([EMCC, test_file('hello_world.c'), '-target', 'wasm32', '-m64'], 'emcc: error: wasm32 target is not compatible with -sMEMORY64')

self.assert_fail([EMCC, test_file('hello_world.c'), '--target=arm64'], 'emcc: error: unsupported target: arm64 (emcc only supports wasm64-unknown-emscripten and wasm32-unknown-emscripten')

Expand Down Expand Up @@ -14701,7 +14705,7 @@ def test_uuid(self):

def test_wasm64_no_asan(self):
expected = 'error: MEMORY64 does not yet work with ASAN'
self.assert_fail([EMCC, test_file('hello_world.c'), '-sMEMORY64', '-fsanitize=address'], expected)
self.assert_fail([EMCC, test_file('hello_world.c'), '-m64', '-fsanitize=address'], expected)

def test_mimalloc_no_asan(self):
# See https://github.com/emscripten-core/emscripten/issues/23288#issuecomment-2571648258
Expand Down
2 changes: 1 addition & 1 deletion test/test_sockets.py
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Expand Up @@ -423,5 +423,5 @@ def test_sockets_send_while_connecting(self):
class sockets64(sockets):
def setUp(self):
super().setUp()
self.set_setting('MEMORY64')
self.cflags.append('-m64')
self.require_wasm64()
4 changes: 2 additions & 2 deletions tools/maint/gen_sig_info.py
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Expand Up @@ -353,8 +353,8 @@ def extract_sig_info(sig_info, extra_settings=None, extra_cflags=None, cxx=False
shared.check_call(cmd)
sig_info32 = extract_sigs(symbols, obj_file)

# Run the same command again with memory64.
shared.check_call(cmd + ['-sMEMORY64'])
# Run the same command again with wasm64.
shared.check_call(cmd + ['-m64'])
sig_info64 = extract_sigs(symbols, obj_file)

for sym, sig32 in sig_info32.items():
Expand Down
2 changes: 1 addition & 1 deletion tools/system_libs.py
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Expand Up @@ -70,7 +70,7 @@ def get_base_cflags(build_dir, force_object_files=False, preprocess=True):
if preprocess:
flags += ['-DEMSCRIPTEN_DYNAMIC_LINKING']
if settings.MEMORY64:
flags += ['-sMEMORY64']
flags += ['-m64']

source_dir = utils.path_from_root()
relative_source_dir = os.path.relpath(source_dir, build_dir)
Expand Down
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