EMSDK 3.1.14: no main argv with PROXY_TO_PTHREAD

[tiran]

EMSDK 3.1.14 no longer passes any argc / argv to the program with linker flag -sPROXY_TO_PTHREAD. This used to work fine with 3.1.13 and earlier versions of Emscripten. It is trival to reproduce with a C program that prints argc.

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.14 (4343cbe)
clang version 15.0.0 (https://github.com/llvm/llvm-project 7effcbda49ba32991b8955821b8fdbd4f8f303e2)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /opt/emsdk/upstream/bin

Failing command line in full:

#include <stdio.h>

int main(int argc, char *argv[])
{
        printf("argc: %i\n", argc);
        return 0;
}

$ emcc -pthread -sUSE_PTHREADS -sPROXY_TO_PTHREAD -sEXIT_RUNTIME main.c -o main.js
$ node --experimental-wasm-threads --experimental-wasm-bulk-memory main.js egg spam
argc: 0

$ emcc -pthread -sUSE_PTHREADS -sEXIT_RUNTIME main.c -o main.js
$ node --experimental-wasm-threads --experimental-wasm-bulk-memory main.js egg spam
argc: 3

[tiran]

WIth emscripten/emsdk:3.1.13 container:

# emcc -v
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.13 (531257621816c200bc7c3be53129494afd029aec)
clang version 15.0.0 (https://github.com/llvm/llvm-project 5c6ed60c517c47b25b6b25d8ac3666d0e746b0c3)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /emsdk/upstream/bin
# emcc -pthread -sUSE_PTHREADS -sPROXY_TO_PTHREAD -sEXIT_RUNTIME main.c -o main.js
# node --experimental-wasm-threads --experimental-wasm-bulk-memory main.js egg spam
argc: 3

[tiran]

In 3.1.14 the callMain function no longer sets up argc and argv like in 3.1.13

function callMain(args) {
  assert(runDependencies == 0, 'cannot call main when async dependencies remain! (listen on Module["onRuntimeInitialized"])');
  assert(__ATPRERUN__.length == 0, 'cannot call main when preRun functions remain to be called');

  // User requested the PROXY_TO_PTHREAD option, so call a stub main which pthread_create()s a new thread
  // that will call the user's real main() for the application.
  var entryFunction = Module['__emscripten_proxy_main'];

  var argc = 0;
  var argv = 0;

  try {

    var ret = entryFunction(argc, argv);

    // In PROXY_TO_PTHREAD builds, we should never exit the runtime below, as
    // execution is asynchronously handed off to a pthread.
    assert(ret == 0, '_emscripten_proxy_main failed to start proxy thread: ' + ret);
  } finally {
    calledMain = true;

  }
}

3.1.13 had this block:

  args = args || [];
  args.unshift(thisProgram);

  var argc = args.length;
  var argv = stackAlloc((argc + 1) * 4);
  var argv_ptr = argv >> 2;
  args.forEach((arg) => {
    HEAP32[argv_ptr++] = allocateUTF8OnStack(arg);
  });
  HEAP32[argv_ptr] = 0;

If I patch the block into my JS file, then argument passing works again.

[tiran]

I suspect that the issue might be related to MAIN_READS_PARAMS setting and new name mangling of __main_argc_argv.

[kripken]

Bisected to

98507fab7b60292533a17cb935c36ccd439694c9 is the first bad commit
commit 98507fab7b60292533a17cb935c36ccd439694c9
Author: chromium-autoroll <[email protected]>
Date:   Fri Jun 10 18:07:56 2022 +0000

    Roll emscripten from b725fbf23815 to b86798af5d70 (2 revisions)
    
    https://chromium.googlesource.com/external/github.com/emscripten-core/emscripten.git/+log/b725fbf23815..b86798af5d70
    
    2022-06-10 [email protected] Move PROXY_TO_PTHREAD handling into native code. NFC (#17153)
    2022-06-10 [email protected] Add support for noexcept keyword to embind.  (#17140)
    
    If this roll has caused a breakage, revert this CL and stop the roller
    using the controls here:
    https://autoroll.skia.org/r/emscripten-emscripten-releases
    Please CC [email protected] on the revert to ensure that a human
    is aware of the problem.
    
    To report a problem with the AutoRoller itself, please file a bug:
    https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug
    
    Documentation for the AutoRoller is here:
    https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
    
    Tbr: [email protected]
    Change-Id: Ic793eb7c43b147e54addb2e321ffe63abf799dcd
    Reviewed-on: https://chromium-review.googlesource.com/c/emscripten-releases/+/3700611
    Bot-Commit: chromium-autoroll <[email protected]>
    Commit-Queue: chromium-autoroll <[email protected]>

 DEPS | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

So I assume #17153 is the cause. cc @sbc100

Also, surprising we don't have a test for this...