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Fix roundtrip behavior for utimesat and stat #27941

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Merged
sbc100 merged 12 commits into from
Oct 14, 2026
Merged

Fix roundtrip behavior for utimesat and stat #27941

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b6ee6d7
Fix roundtrip behavior for utimesat and stat
hoodmane Oct 9, 2026
6bf480a
Fix tests
hoodmane Oct 13, 2026
923a7bf
Mark test crossplatform
hoodmane Oct 13, 2026
91bb91e
Fix code sizes
hoodmane Oct 13, 2026
25f2f38
Update code sizes
hoodmane Oct 13, 2026
e20c1d6
Fix test in wasmfs
hoodmane Oct 13, 2026
c2d7ec2
Merge branch 'main' into fix-utimes-stat-roundtrip
hoodmane Oct 13, 2026
9238b1e
Don't use static in tests
hoodmane Oct 13, 2026
26ebc88
Remove another static
hoodmane Oct 13, 2026
9d95e29
Update codesizes
hoodmane Oct 13, 2026
f595b4e
Merge branch 'main' into fix-utimes-stat-roundtrip
hoodmane Oct 14, 2026
15e9f79
Update code size
hoodmane Oct 14, 2026
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5 changes: 0 additions & 5 deletions src/lib/libmemfs.js
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Original file line number Diff line number Diff line change
Expand Up @@ -156,11 +156,6 @@ addToLibrary({
attr.atime = new Date(node.atime);
attr.mtime = new Date(node.mtime);
attr.ctime = new Date(node.ctime);
// A Date only holds whole milliseconds: also return the exact times
// (e.g. as set by utimensat), which SYSCALLS.writeStat prefers.
attr.atimeMs = node.atime;
attr.mtimeMs = node.mtime;
attr.ctimeMs = node.ctime;
// NOTE: In our implementation, st_blocks = Math.ceil(st_size/st_blksize),
// but this is not required by the standard.
attr.blksize = 4096;
Expand Down
3 changes: 0 additions & 3 deletions src/lib/libnodefs.js
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Expand Up @@ -140,9 +140,6 @@ addToLibrary({
atime: stat.atime,
mtime: stat.mtime,
ctime: stat.ctime,
atimeMs: stat.atimeMs,
mtimeMs: stat.mtimeMs,
ctimeMs: stat.ctimeMs,
blksize: stat.blksize,
blocks: stat.blocks
};
Expand Down
20 changes: 7 additions & 13 deletions src/lib/libsyscall.js
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Expand Up @@ -48,18 +48,15 @@ var SyscallsLibrary = {
{{{ makeSetValue('buf', C_STRUCTS.stat.st_size, 'stat.size', 'i64') }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_blksize, '4096', 'i32') }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_blocks, 'stat.blocks', 'i32') }}};
// Prefer `*Ms` properties if available (e.g. from MEMFS, or NODEFS / host
// `fs.Stats`) for sub-millisecond precision; fall back to Date#getTime for
// other filesystems.
var atime = stat.atimeMs ?? stat.atime.getTime();
var mtime = stat.mtimeMs ?? stat.mtime.getTime();
var ctime = stat.ctimeMs ?? stat.ctime.getTime();
var atime = stat.atime.getTime();
var mtime = stat.mtime.getTime();
var ctime = stat.ctime.getTime();
{{{ makeSetValue('buf', C_STRUCTS.stat.st_atim.tv_sec, 'Math.floor(atime / 1000)', 'i64') }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_atim.tv_nsec, 'Math.floor((atime % 1000) * 1_000_000)', SIZE_TYPE) }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_atim.tv_nsec, '(atime % 1000) * 1000 * 1000', SIZE_TYPE) }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_mtim.tv_sec, 'Math.floor(mtime / 1000)', 'i64') }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_mtim.tv_nsec, 'Math.floor((mtime % 1000) * 1_000_000)', SIZE_TYPE) }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_mtim.tv_nsec, '(mtime % 1000) * 1000 * 1000', SIZE_TYPE) }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_ctim.tv_sec, 'Math.floor(ctime / 1000)', 'i64') }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_ctim.tv_nsec, 'Math.floor((ctime % 1000) * 1_000_000)', SIZE_TYPE) }}};

@sbc100 sbc100 Oct 9, 2026

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Can you keep the new 1_000_000 syntax?

Does removing Math.floor here have any semantic difference?

@hoodmane hoodmane Oct 13, 2026

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Do you want 1_000? I don't see anywhere in the codebase that says that, the _ is only used in numbers at least 5 digits. But I can put it in.

I don't think Math.floor() makes a difference, no.

{{{ makeSetValue('buf', C_STRUCTS.stat.st_ctim.tv_nsec, '(ctime % 1000) * 1000 * 1000', SIZE_TYPE) }}};
{{{ makeSetValue('buf', C_STRUCTS.stat.st_ino, 'stat.ino', 'i64') }}};
return 0;
},
Expand Down Expand Up @@ -1092,10 +1089,7 @@ var SyscallsLibrary = {
return null;
}
var tv_sec = {{{ makeGetValue('ptr', C_STRUCTS.timespec.tv_sec, 'i53') }}};
// Round down tv_nsec to the nearest 10 microseconds (10,000 ns) to prevent
// floating-point rounding into the next whole second when converting to host/Windows timestamps.
tv_nsec = (tv_nsec / 10_000 | 0) * 10_000;
return (tv_sec + (tv_nsec / 1_000_000_000)) * 1000;
return (tv_sec*1000) + Math.floor(tv_nsec/(1000*1000));
}
atime = readTimespec(times);
mtime = readTimespec(times + {{{ C_STRUCTS.timespec.__size__ }}});
Expand Down
6 changes: 1 addition & 5 deletions system/lib/wasmfs/syscalls.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,6 @@

#define _LARGEFILE64_SOURCE // For F_GETLK64 etc

#include <cmath>
#include <dirent.h>
#include <emscripten/emscripten.h>
#include <emscripten/heap.h>
Expand Down Expand Up @@ -1139,10 +1138,7 @@ static double timespec_to_ms(timespec ts) {
if (ts.tv_nsec == UTIME_NOW) {
return emscripten_date_now();
}
// Round down tv_nsec to the nearest 10 microseconds (10,000 ns) to prevent
// floating-point rounding into the next whole second when converting to host/Windows timestamps.
long tv_nsec_10us = (ts.tv_nsec / 10000) * 10000;
return (double(ts.tv_sec) + double(tv_nsec_10us) / 1e9) * 1000;
return double(ts.tv_sec) * 1000 + double(ts.tv_nsec / (1000 * 1000));
}

// TODO: Test this with non-AT_FDCWD values.
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_ctors1.json
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@@ -1,10 +1,10 @@
{
"a.out.js": 19180,
"a.out.js.gz": 8091,
"a.out.js": 19126,
"a.out.js.gz": 8079,
"a.out.nodebug.wasm": 133999,
"a.out.nodebug.wasm.gz": 51252,
"total": 153179,
"total_gz": 59343,
"total": 153125,
"total_gz": 59331,
"sent": [
"__cxa_throw",
"_abort_js",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_ctors2.json
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@@ -1,10 +1,10 @@
{
"a.out.js": 19157,
"a.out.js.gz": 8074,
"a.out.js": 19103,
"a.out.js.gz": 8063,
"a.out.nodebug.wasm": 133427,
"a.out.nodebug.wasm.gz": 50944,
"total": 152584,
"total_gz": 59018,
"total": 152530,
"total_gz": 59007,
"sent": [
"__cxa_throw",
"_abort_js",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_except.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 22874,
"a.out.js.gz": 9053,
"a.out.js": 22820,
"a.out.js.gz": 9041,
"a.out.nodebug.wasm": 176407,
"a.out.nodebug.wasm.gz": 58760,
"total": 199281,
"total_gz": 67813,
"total": 199227,
"total_gz": 67801,
"sent": [
"__cxa_begin_catch",
"__cxa_end_catch",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_except_wasm.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 18979,
"a.out.js.gz": 8010,
"a.out.js": 18925,
"a.out.js.gz": 7999,
"a.out.nodebug.wasm": 149664,
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"total": 168643,
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"total": 168589,
"total_gz": 64299,
"sent": [
"_abort_js",
"_tzset_js",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_except_wasm_legacy.json
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@@ -1,10 +1,10 @@
{
"a.out.js": 19057,
"a.out.js.gz": 8033,
"a.out.js": 19003,
"a.out.js.gz": 8022,
"a.out.nodebug.wasm": 147446,
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"total": 166503,
"total_gz": 63996,
"total": 166449,
"total_gz": 63985,
"sent": [
"_abort_js",
"_tzset_js",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_lto.json
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@@ -1,10 +1,10 @@
{
"a.out.js": 18520,
"a.out.js.gz": 7786,
"a.out.js": 18466,
"a.out.js.gz": 7775,
"a.out.nodebug.wasm": 101050,
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"total": 119570,
"total_gz": 46073,
"total": 119516,
"total_gz": 46062,
"sent": [
"a (emscripten_resize_heap)",
"b (_setitimer_js)",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_mangle.json
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@@ -1,10 +1,10 @@
{
"a.out.js": 22924,
"a.out.js.gz": 9073,
"a.out.js": 22870,
"a.out.js.gz": 9061,
"a.out.nodebug.wasm": 242687,
"a.out.nodebug.wasm.gz": 80983,
"total": 265611,
"total_gz": 90056,
"total": 265557,
"total_gz": 90044,
"sent": [
"__cxa_begin_catch",
"__cxa_end_catch",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_noexcept.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 19180,
"a.out.js.gz": 8091,
"a.out.js": 19126,
"a.out.js.gz": 8079,
"a.out.nodebug.wasm": 135906,
"a.out.nodebug.wasm.gz": 51862,
"total": 155086,
"total_gz": 59953,
"total": 155032,
"total_gz": 59941,
"sent": [
"__cxa_throw",
"_abort_js",
Expand Down
20 changes: 6 additions & 14 deletions test/codesize/test_codesize_file_preload.expected.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1074,11 +1074,6 @@ var MEMFS = {
attr.atime = new Date(node.atime);
attr.mtime = new Date(node.mtime);
attr.ctime = new Date(node.ctime);
// A Date only holds whole milliseconds: also return the exact times
// (e.g. as set by utimensat), which SYSCALLS.writeStat prefers.
attr.atimeMs = node.atime;
attr.mtimeMs = node.mtime;
attr.ctimeMs = node.ctime;
// NOTE: In our implementation, st_blocks = Math.ceil(st_size/st_blksize),
// but this is not required by the standard.
attr.blksize = 4096;
Expand Down Expand Up @@ -3029,18 +3024,15 @@ var SYSCALLS = {
HEAP64[(((buf) + (24)) >> 3)] = BigInt(stat.size);
HEAP32[(((buf) + (32)) >> 2)] = 4096;
HEAP32[(((buf) + (36)) >> 2)] = stat.blocks;
// Prefer `*Ms` properties if available (e.g. from MEMFS, or NODEFS / host
// `fs.Stats`) for sub-millisecond precision; fall back to Date#getTime for
// other filesystems.
var atime = stat.atimeMs ?? stat.atime.getTime();
var mtime = stat.mtimeMs ?? stat.mtime.getTime();
var ctime = stat.ctimeMs ?? stat.ctime.getTime();
var atime = stat.atime.getTime();
var mtime = stat.mtime.getTime();
var ctime = stat.ctime.getTime();
HEAP64[(((buf) + (40)) >> 3)] = BigInt(Math.floor(atime / 1e3));
HEAPU32[(((buf) + (48)) >> 2)] = Math.floor((atime % 1e3) * 1e6);
HEAPU32[(((buf) + (48)) >> 2)] = (atime % 1e3) * 1e3 * 1e3;
HEAP64[(((buf) + (56)) >> 3)] = BigInt(Math.floor(mtime / 1e3));
HEAPU32[(((buf) + (64)) >> 2)] = Math.floor((mtime % 1e3) * 1e6);
HEAPU32[(((buf) + (64)) >> 2)] = (mtime % 1e3) * 1e3 * 1e3;
HEAP64[(((buf) + (72)) >> 3)] = BigInt(Math.floor(ctime / 1e3));
HEAPU32[(((buf) + (80)) >> 2)] = Math.floor((ctime % 1e3) * 1e6);
HEAPU32[(((buf) + (80)) >> 2)] = (ctime % 1e3) * 1e3 * 1e3;
HEAP64[(((buf) + (88)) >> 3)] = BigInt(stat.ino);
return 0;
},
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_file_preload.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 22232,
"a.out.js.gz": 9258,
"a.out.js": 22178,
"a.out.js.gz": 9246,
"a.out.nodebug.wasm": 1198,
"a.out.nodebug.wasm.gz": 730,
"total": 23430,
"total_gz": 9988,
"total": 23376,
"total_gz": 9976,
"sent": [
"a (fd_write)"
],
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_files_js_fs.json
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@@ -1,10 +1,10 @@
{
"a.out.js": 17831,
"a.out.js.gz": 7432,
"a.out.js": 17777,
"a.out.js.gz": 7410,
"a.out.nodebug.wasm": 381,
"a.out.nodebug.wasm.gz": 258,
"total": 18212,
"total_gz": 7690,
"total": 18158,
"total_gz": 7668,
"sent": [
"a (fd_write)",
"b (fd_read)",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_hello_dylink.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 26380,
"a.out.js.gz": 11230,
"a.out.js": 26268,
"a.out.js.gz": 11199,
"a.out.nodebug.wasm": 16986,
"a.out.nodebug.wasm.gz": 8672,
"total": 43366,
"total_gz": 19902,
"total": 43254,
"total_gz": 19871,
"sent": [
"__syscall_stat64",
"emscripten_resize_heap",
Expand Down
4 changes: 2 additions & 2 deletions test/codesize/test_codesize_hello_dylink_all.json
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
{
"a.out.js": 272661,
"a.out.js": 272550,
"a.out.nodebug.wasm": 587934,
"total": 860595,
"total": 860484,
"sent": [
"IMG_Init",
"IMG_Load",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_no_closure_code_size.json
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Expand Up @@ -11,10 +11,10 @@
"strict.js.gz": 2296,
"strict.wasm": 1188,
"strict.wasm.gz": 733,
"files.js": 53945,
"files.js.gz": 15176,
"files.js": 53807,
"files.js.gz": 15143,
"files.wasm": 371,
"files.wasm.gz": 264,
"total": 77816,
"total_gz": 25071
"total": 77678,
"total_gz": 25038
}
47 changes: 0 additions & 47 deletions test/fs/test_fs_subms_times.c
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This file was deleted.

6 changes: 0 additions & 6 deletions test/test_core.py
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Expand Up @@ -5977,12 +5977,6 @@ def test_fs_write(self):
self.set_setting("FORCE_FILESYSTEM")
self.do_runf_out_file('fs/test_fs_write.c')

@crossplatform
@with_all_fs
@no_deno('https://github.com/emscripten-core/emscripten/pull/27890')
def test_fs_subms_times(self):
self.do_runf('fs/test_fs_subms_times.c', 'done\n')

@with_all_fs
def test_fs_access_mode(self):
# Writing to an O_RDONLY fd and reading from an O_WRONLY fd must fail with
Expand Down
8 changes: 8 additions & 0 deletions test/test_other.py
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Expand Up @@ -5811,6 +5811,14 @@ def test_strftime_zZ(self):
def test_strptime_symmetry(self):
self.do_other_test('test_strptime_symmetry.c')

def test_utime_now(self):
self.do_runf('utime/test_utime_now.c', 'done\n')

@crossplatform
@also_with_nodefs_both
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def test_utime_roundtrip(self):
self.do_runf('utime/test_utime_roundtrip.c', 'done\n')

@also_with_wasmfs
def test_truncate_from_0(self):
self.do_other_test('test_truncate_from_0.cpp')
Expand Down
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