SUPPORT_BIG_ENDIAN+PThread does not work on big-endian machines

[slavek-kucera]

Trivial program (int main(){}) fails during startup with the following error messages

TypeError: wait.value.then is not a function
    at __emscripten_thread_mailbox_await (***/main.js:1:19568)
    at wasm://wasm/00015506:wasm-function[14]:0x553
    at callRuntimeCallbacks (***/main.js:1:17193)
    at initRuntime (***/main.js:1:7154)
    at doRun (***/main.js:1:27532)
    at run (***/main.js:1:27802)
    at removeRunDependency (***/main.js:1:8194)
    at ***/main.js:1:14279

while running on a big-endian machine with PThreads and SUPPORT_BIG_ENDIAN.

Using emscriptern 4.0.2., I built the program with the following command:

em++ -o main.js -s USE_PTHREADS=1 -s PROXY_TO_PTHREAD=1 -s PTHREAD_POOL_SIZE=8 -s SUPPORT_BIG_ENDIAN=1 -pthread -s EXIT_RUNTIME=1 -s ALLOW_MEMORY_GROWTH=1 -O2 main.cpp

If I manually adjust (byteswap) values in the following code (both pthread_ptr in Atomics.waitAsync and 1 in Atomics.store), everything starts working again

emscripten/src/lib/libpthread.js

Lines 1231 to 1237 in 2e2ec08

	var wait = Atomics.waitAsync(HEAP32, {{{ getHeapOffset('pthread_ptr', 'i32') }}}, pthread_ptr);
	#if ASSERTIONS
	assert(wait.async);
	#endif
	wait.value.then(checkMailbox);
	var waitingAsync = pthread_ptr + {{{ C_STRUCTS.pthread.waiting_async }}};
	Atomics.store(HEAP32, {{{ getHeapOffset('waitingAsync', 'i32') }}}, 1);

[sbc100]

The SUPPORT_BIG_ENDIAN setting has very little testing to I suppose its no surprise that bugs like this exist.

Can I ask, are you actually targeting bigendian hardware? Are you targeting node or the browser on this hardware?

If you understand the problem would have time to send a PR, and perhaps expand our test coverage for this setting?

[slavek-kucera]

Yes, I was trying to run under node on big-endian machine.

[slavek-kucera]

As for a PR, I can try looking into that.

[cwoffenden]

What machine and OS are you using? We’ve a bunch if BE machines at work mostly as relics but I wouldn’t mind taking a look out of curiosity.

Besides the obvious Mac G5 we’ve also a Talos II (44-core/176-thread POWER9 currently running Debian in LE but can boot BE). And literally a storage room of others but they’re either too old (IRIX) or too rare to be feasible (devkits).