Make longjmp/exceptions helpers thread-safe

system/lib/libc/emscripten_exception_builtins.c

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2018 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ */
+
+/*
+  References to these longjmp- and exceptions-supporting things are generated
+  in the llvm backend.
+
+  Note that these might make more sense in compiler-rt, but they need to be
+  built with multithreading support when relevant (to avoid races between
+  threads that throw at the same time etc.), and compiler-rt is not built
+  that way atm.
+*/
+
+int _Thread_local __THREW__ = 0;
+int _Thread_local __threwValue = 0;
+
+void setThrew(int threw, int value) {
+  if (__THREW__ == 0) {
+    __THREW__ = threw;
+    __threwValue = value;
+  }
+}

system/lib/libc/extras.c

@@ -30,4 +30,3 @@ long* _get_timezone() {
 
 void __lock(void* ptr) {}
 void __unlock(void* ptr) {}
-

tests/core/pthread/exceptions.cpp

@@ -0,0 +1,78 @@
+// Copyright 2019 The Emscripten Authors.  All rights reserved.
+// Emscripten is available under two separate licenses, the MIT license and the
+// University of Illinois/NCSA Open Source License.  Both these licenses can be
+// found in the LICENSE file.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <assert.h>
+#include <emscripten.h>
+
+#include <atomic>
+
+#define NUM_THREADS 2
+#define TOTAL 1000
+#define THREAD_ADDS 750
+#define MAIN_ADDS 5
+
+static std::atomic<int> sum;
+static std::atomic<int> total;
+
+void *ThreadMain(void *arg) {
+  for (int i = 0; i < TOTAL; i++) {
+    try {
+      // Throw two different types, to make sure we check throwing and landing
+      // pad behavior.
+      if (i & 3) {
+        throw 3.14159f;
+      }
+      throw i;
+    } catch (int x) {
+      total += x;
+    } catch (float f) {
+      sum++;
+      // wait for a change, so we see interleaved processing.
+      int last = sum.load();
+      while (sum.load() == last) {}
+    }
+  }
+  pthread_exit((void*)TOTAL);
+}
+
+pthread_t thread[NUM_THREADS];
+
+void CreateThread(int i)
+{
+  pthread_attr_t attr;
+  pthread_attr_init(&attr);
+  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
+  static int counter = 1;
+  int rc = pthread_create(&thread[i], &attr, ThreadMain, (void*)i);
+  assert(rc == 0);
+  pthread_attr_destroy(&attr);
+}
+
+void loop() {
+  static int main_adds = 0;
+  int worker_adds = sum.load() - main_adds;
+  sum++;
+  main_adds++;
+  printf("main iter %d : %d\n", main_adds, worker_adds);
+  if (worker_adds == NUM_THREADS * THREAD_ADDS &&
+      main_adds >= MAIN_ADDS) {
+    printf("done: %d.\n", total.load());
+    emscripten_cancel_main_loop();
+    exit(0);
+  }
+}
+
+int main() {
+  // Create initial threads.
+  for(int i = 0; i < NUM_THREADS; ++i) {
+    printf("maek\n");
+    CreateThread(i);
+  }
+
+  emscripten_set_main_loop(loop, 0, 0);
+}

tests/core/pthread/exceptions.out

@@ -0,0 +1 @@
+done: 249000.

tests/test_core.py

@@ -8248,6 +8248,12 @@ def test():
     self.emcc_args += ['-DPOOL']
     test()
 
+  @node_pthreads
+  def test_pthread_exceptions(self):
+    self.set_setting('PTHREAD_POOL_SIZE', '2')
+    self.emcc_args += ['-fexceptions']
+    self.do_run_in_out_file_test('tests', 'core', 'pthread', 'exceptions.cpp')
+
   def test_emscripten_atomics_stub(self):
     self.do_run_in_out_file_test('tests', 'core', 'pthread', 'emscripten_atomics.c')
 

tools/system_libs.py

@@ -643,7 +643,6 @@ class libcompiler_rt(Library):
   cflags = ['-O2', '-fno-builtin']
   src_dir = ['system', 'lib', 'compiler-rt', 'lib', 'builtins']
   src_files = glob_in_path(src_dir, '*.c')
-  src_files.append(shared.path_from_root('system', 'lib', 'compiler-rt', 'extras.c'))
   src_files.append(shared.path_from_root('system', 'lib', 'compiler-rt', 'stack_ops.s'))
   src_files.append(shared.path_from_root('system', 'lib', 'compiler-rt', 'emscripten_setjmp.c'))
 
@@ -743,7 +742,7 @@ def get_files(self):
 
     libc_files += files_in_path(
         path_components=['system', 'lib', 'libc'],
-        filenames=['extras.c', 'wasi-helpers.c'])
+        filenames=['emscripten_exception_builtins.c', 'extras.c', 'wasi-helpers.c'])
 
     return libc_files