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[ASYNCIFY] Run continuations under callUserCallback #26095

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[ASYNCIFY] Run continuations under callUserCallback #26095

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11 changes: 4 additions & 7 deletions src/lib/libasync.js
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Original file line number Diff line number Diff line change
Expand Up @@ -323,10 +323,9 @@ addToLibrary({
// can just call the function with no args at all since the engine will produce zeros
// for all arguments. However, for i64 arguments we get `undefined cannot be converted to
// BigInt`.
return func(...Asyncify.restoreRewindArguments(original));
#else
return func();
func = func.bind(0, ...Asyncify.restoreRewindArguments(original));
#endif
return callUserCallback(func);
},

// This receives a function to call to start the async operation, and
Expand Down Expand Up @@ -480,9 +479,8 @@ addToLibrary({
#endif
},

emscripten_sleep__deps: ['$safeSetTimeout'],
emscripten_sleep__async: true,
emscripten_sleep: (ms) => Asyncify.handleSleep((wakeUp) => safeSetTimeout(wakeUp, ms)),
emscripten_sleep: (ms) => Asyncify.handleSleep((wakeUp) => setTimeout(wakeUp, ms)),

emscripten_wget_data__deps: ['$asyncLoad', 'malloc'],
emscripten_wget_data__async: 'auto',
Expand All @@ -501,15 +499,14 @@ addToLibrary({
}
},

emscripten_scan_registers__deps: ['$safeSetTimeout'],
emscripten_scan_registers__async: true,
emscripten_scan_registers: (func) => {
return Asyncify.handleSleep((wakeUp) => {
// We must first unwind, so things are spilled to the stack. Then while
// we are pausing we do the actual scan. After that we can resume. Note
// how using a timeout here avoids unbounded call stack growth, which
// could happen if we tried to scan the stack immediately after unwinding.
safeSetTimeout(() => {
setTimeout(() => {
var stackBegin = Asyncify.currData + {{{ C_STRUCTS.asyncify_data_s.__size__ }}};
var stackEnd = {{{ makeGetValue('Asyncify.currData', 0, '*') }}};
{{{ makeDynCall('vpp', 'func') }}}(stackBegin, stackEnd);
Expand Down
8 changes: 6 additions & 2 deletions src/lib/libcore.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1996,6 +1996,9 @@ addToLibrary({
err('Stack overflow detected. You can try increasing -sSTACK_SIZE (currently set to {{{ STACK_SIZE }}})');
}
}
#endif
#if RUNTIME_DEBUG
dbg("handleException: got unexpected exception, calling quit_")
#endif
quit_(1, e);
},
Expand Down Expand Up @@ -2066,10 +2069,11 @@ addToLibrary({
return;
}
try {
func();
maybeExit();
return func();
} catch (e) {
handleException(e);
} finally {
maybeExit();
}
},

Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_cxx_lto.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 18993,
"a.out.js.gz": 7823,
"a.out.js": 19001,
"a.out.js.gz": 7824,
"a.out.nodebug.wasm": 106448,
"a.out.nodebug.wasm.gz": 42638,
"total": 125441,
"total_gz": 50461,
"total": 125449,
"total_gz": 50462,
"sent": [
"a (emscripten_resize_heap)",
"b (_setitimer_js)",
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": 244848,
"a.out.js": 244863,
"a.out.nodebug.wasm": 577879,
"total": 822727,
"total": 822742,
"sent": [
"IMG_Init",
"IMG_Load",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_minimal_pthreads.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 7722,
"a.out.js.gz": 3812,
"a.out.js": 7737,
"a.out.js.gz": 3816,
"a.out.nodebug.wasm": 19604,
"a.out.nodebug.wasm.gz": 9079,
"total": 27326,
"total_gz": 12891,
"total": 27341,
"total_gz": 12895,
"sent": [
"a (memory)",
"b (emscripten_get_now)",
Expand Down
8 changes: 4 additions & 4 deletions test/codesize/test_codesize_minimal_pthreads_memgrowth.json
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
{
"a.out.js": 8145,
"a.out.js.gz": 4011,
"a.out.js": 8160,
"a.out.js.gz": 4015,
"a.out.nodebug.wasm": 19605,
"a.out.nodebug.wasm.gz": 9080,
"total": 27750,
"total_gz": 13091,
"total": 27765,
"total_gz": 13095,
"sent": [
"a (memory)",
"b (emscripten_get_now)",
Expand Down
3 changes: 0 additions & 3 deletions test/embind_with_asyncify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,5 @@ int main() {
val async_text = response.call<val>("text");
std::string text = async_text.await().as<std::string>();
assert(text == "foo");
// This explicit exit() should not be necessary here.
// TODO(https://github.com/emscripten-core/emscripten/issues/26093)
exit(0);
return 0;
}
6 changes: 1 addition & 5 deletions test/test_async_exit_after_wakeup.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2,11 +2,7 @@ addToLibrary({
async_func__async: true,
async_func: (value) => {
return Asyncify.handleSleep((wakeUp) => {
// Currently with -sASYNCIFY the wakeUp call needs to be wrapped in
// callUserCallback, otherwise things like `exit()` won't work from
// the continuation.
// TODO(https://github.com/emscripten-core/emscripten/issues/26093)
setTimeout(() => callUserCallback(() => wakeUp(42)), 0);
setTimeout(() => wakeUp(42), 0);
});
},
});
2 changes: 1 addition & 1 deletion test/test_core.py
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Original file line number Diff line number Diff line change
Expand Up @@ -9587,7 +9587,7 @@ def test_embind_lib_with_asyncify(self, args):
'-sINCOMING_MODULE_JS_API=onRuntimeInitialized',
]
self.cflags += args
self.do_core_test('embind_lib_with_asyncify.cpp')
self.do_core_test('embind_lib_with_asyncify.cpp', assert_returncode=NON_ZERO)
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@kripken kripken Jan 13, 2026

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Why does this change?

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@sbc100 sbc100 Jan 13, 2026

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The reason is that because the asyncify continuation are now run in callUserCallback the handleException: got unexpected exception, calling quit_` which sets the node exit code to non-zero.

This test explicit has delayed_throw in it which throws and exception in an asyncify continuation.

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@kripken kripken Jan 14, 2026

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But that delayed throw is handled early in the test,

    let delayedThrowResult = Module["delayed_throw"]();
    assert(delayedThrowResult instanceof Promise);
    let err = await delayedThrowResult.then(() => '', err => err.message);
    assert(err === 'my message', `"${err}" doesn't contain the expected error`);

The rest of the test runs after those lines, and it exits without error?

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@sbc100 sbc100 Jan 14, 2026

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The .then(() => '', err => err.message); part handles the error, but the exit code is remembered because handleExcetpion calls quit_ which under node sets the overall process exit code:

emscripten/src/shell.js

Line 253 in 48a147b

process.exitCode = status;

So its kind of like the node implementation is remember the exit code even though the exception was handled further up. I don't know if this is ideal, but I imagine changing it would be very hard at this point.

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@kripken kripken Jan 14, 2026

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I see. Yeah, probably not worth changing.

How about adding a comment in the python file, explaining why we expect the test to fail? Otherwise it is quite surprising I think.

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@sbc100 sbc100 Jan 14, 2026

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Agreed


@no_asan('asyncify stack operations confuse asan')
@with_asyncify_and_jspi
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