Revert "Use __stdio_exit rather then fflush(0) on exit (#16130)" (#17046)

This reverts commit eff9ae7.

I decided to go this route rather than try to keeping
`__stdio_exit` as in #17044.

Author: sbc100

ChangeLog.md

@@ -22,6 +22,8 @@ See docs/process.md for more on how version tagging works.
 ------
 - Fix crash, introduced in 3.1.11, which occurred when using pointer types
   (types ending in `*`) with getValue/setValue library functions. (#17028)
+- Fix possible deadlock in multi-threaded builds that use EXIT_RUNTIME=0 with
+  ASSERTIONS enabled. This was introduced in 3.1.3 as part of #16130. (#17044)
 
 3.1.11 - 05/21/2022
 -------------------

emcc.py

@@ -2100,12 +2100,11 @@ def phase_linker_setup(options, state, newargs, user_settings):
       ]
 
     if not settings.STANDALONE_WASM and (settings.EXIT_RUNTIME or settings.ASSERTIONS):
-      # We use __stdio_exit to shut down musl's stdio subsystems and flush
-      # streams on exit.
-      # We only include it if the runtime is exitable, or when ASSERTIONS
+      # to flush streams on FS exit, we need to be able to call fflush
+      # we only include it if the runtime is exitable, or when ASSERTIONS
       # (ASSERTIONS will check that streams do not need to be flushed,
       # helping people see when they should have enabled EXIT_RUNTIME)
-      settings.EXPORT_IF_DEFINED += ['__stdio_exit']
+      settings.EXPORT_IF_DEFINED += ['fflush']
 
     if settings.SUPPORT_ERRNO:
       # so setErrNo JS library function can report errno back to C

src/library_fs.js

@@ -1489,10 +1489,9 @@ FS.staticInit();` +
     },
     quit: () => {
       FS.init.initialized = false;
-      // Call musl-internal function to close all stdio streams, so nothing is
-      // left in internal buffers.
-#if hasExportedFunction('___stdio_exit')
-      ___stdio_exit();
+      // force-flush all streams, so we get musl std streams printed out
+#if hasExportedFunction('_fflush')
+      _fflush(0);
 #endif
       // close all of our streams
       for (var i = 0; i < FS.streams.length; i++) {

src/library_wasi.js

@@ -231,8 +231,8 @@ var WasiLibrary = {
   $flush_NO_FILESYSTEM__deps: ['$printChar', '$printCharBuffers'],
   $flush_NO_FILESYSTEM: function() {
     // flush anything remaining in the buffers during shutdown
-#if hasExportedFunction('___stdio_exit')
-    ___stdio_exit();
+#if hasExportedFunction('_fflush')
+    _fflush(0);
 #endif
     if (printCharBuffers[1].length) printChar(1, {{{ charCode("\n") }}});
     if (printCharBuffers[2].length) printChar(2, {{{ charCode("\n") }}});

src/postamble.js

@@ -371,11 +371,10 @@ function checkUnflushedContent() {
     has = true;
   }
   try { // it doesn't matter if it fails
-#if SYSCALLS_REQUIRE_FILESYSTEM == 0
-    var flush = {{{ '$flush_NO_FILESYSTEM' in addedLibraryItems ? 'flush_NO_FILESYSTEM' : 'null' }}};
-    if (flush) flush();
-#elif hasExportedFunction('___stdio_exit')
-    ___stdio_exit();
+#if SYSCALLS_REQUIRE_FILESYSTEM == 0 && '$flush_NO_FILESYSTEM' in addedLibraryItems
+    flush_NO_FILESYSTEM();
+#elif hasExportedFunction('_fflush')
+    _fflush(0);
 #endif
 #if '$FS' in addedLibraryItems && '$TTY' in addedLibraryItems
     // also flush in the JS FS layer

src/postamble_minimal.js

@@ -32,12 +32,12 @@ function run() {
 
 #endif
 
-#if IN_TEST_HARNESS && hasExportedFunction('___stdio_exit')
+#if IN_TEST_HARNESS && hasExportedFunction('_flush')
   // flush any stdio streams for test harness, since there are existing
   // tests that depend on this behavior.
   // For production use, instead print full lines to avoid this kind of lazy
   // behavior.
-  ___stdio_exit();
+  _fflush();
 #endif
 
 #if EXIT_RUNTIME

src/runtime_wasm64.js

@@ -28,7 +28,7 @@ function instrumentWasmExportsForMemory64(exports) {
           var r = Number(original(BigInt(x ? x : 0)));
           return r;
         };
-      } else if (['setThrew', 'free', 'stackRestore', '__cxa_is_pointer_type'].includes(name)) {
+      } else if (['fflush', 'setThrew', 'free', 'stackRestore', '__cxa_is_pointer_type'].includes(name)) {
         // get one i64
         replacement = (x) => {
           original(BigInt(x));

tests/other/metadce/test_metadce_hello_O0.exports

@@ -1,12 +1,12 @@
 __errno_location
 __indirect_function_table
-__stdio_exit
 __wasm_call_ctors
 dynCall_jiji
 emscripten_stack_get_base
 emscripten_stack_get_end
 emscripten_stack_get_free
 emscripten_stack_init
+fflush
 main
 memory
 stackAlloc

tests/other/metadce/test_metadce_hello_O0.funcs

@@ -10,22 +10,23 @@ $__lockfile
 $__lshrti3
 $__memcpy
 $__ofl_lock
+$__ofl_unlock
 $__original_main
-$__stdio_exit
 $__stdio_write
 $__syscall_getpid
 $__towrite
 $__trunctfdf2
+$__unlock
 $__unlockfile
 $__vfprintf_internal
 $__wasi_syscall_ret
 $__wasm_call_ctors
-$close_file
 $dynCall_jiji
 $emscripten_stack_get_base
 $emscripten_stack_get_end
 $emscripten_stack_get_free
 $emscripten_stack_init
+$fflush
 $fmt_fp
 $fmt_o
 $fmt_u

tests/other/metadce/test_metadce_hello_O0.jssize

@@ -1 +1 @@
-27043
+26996