Nondeterminism checker tool (emscripten-core#6263) [ci skip]

kripken · web-flow · commit dfd3e71f0e1e · 2018-03-05T13:07:07.000-08:00
diff --git a/tools/determinism_checker.py b/tools/determinism_checker.py
@@ -0,0 +1,57 @@
+'''
+Runs a build command many times to search for any nondeterminism.
+'''
+
+import os
+import random
+import shutil
+import subprocess
+import time
+
+def run():
+  subprocess.check_call(['emcc', 'src.cpp', '-O2', '-s', 'WASM=1'])
+  ret = {}
+  for relevant_file in os.listdir('.'):
+    ret[relevant_file] = open(relevant_file).read()
+  return ret
+
+def write(data, subdir):
+  if not os.path.exists(subdir):
+    os.mkdir(subdir)
+  for relevant_file in data.keys():
+    open(os.path.join(subdir, relevant_file), 'w').write(data[relevant_file])
+
+old = os.getcwd()
+try:
+  os.chdir('/tmp/emscripten_temp')
+  assert len(os.listdir('.')) == 0, 'temp dir should start out empty, after that, everything there looks important to us'
+  open('src.cpp', 'w').write('''
+    #include <iostream>
+
+    int main()
+    {
+      std::cout << "hello world" << std::endl << 77 << "." << std::endl;
+      return 0;
+    }
+  ''')
+
+  os.environ['EMCC_DEBUG'] = '1'
+  #os.environ['BINARYEN_PASS_DEBUG'] = '3'
+
+  first = run()
+
+  i = 0
+  while 1:
+    print(i)
+    i += 1
+    time.sleep(random.random()/(10*5)) # add some timing nondeterminism here, not that we need it, but whatever
+    curr = run()
+    if first != curr:
+      print('NONDETERMINISM!!!1')
+      write(first, 'first')
+      write(curr, 'second')
+      break
+
+finally:
+  os.chdir(old)
+
