PyTorch Python fork fix (#291)

* PyTorch Python fork fix

- fixes issue where forking process in PyTorch causes omnitrace/__main__.py to fail due to missing script argument

* Update source/python/omnitrace/__main__.py

Remove debugging "print" LOC

source/python/omnitrace/__main__.py

@@ -40,7 +40,7 @@
 import traceback
 
 PY3 = sys.version_info[0] == 3
-
+_OMNITRACE_PYTHON_SCRIPT_FILE = None
 
 # Python 3.x compatibility utils: execfile
 try:
@@ -270,27 +270,27 @@ def run(prof, cmd):
     prof.runctx(code, globs, None)
 
 
-def main():
+def main(main_args=sys.argv):
     """Main function"""
 
     opts = None
     argv = None
-    if "--" in sys.argv:
-        _idx = sys.argv.index("--")
-        _argv = sys.argv[(_idx + 1) :]
-        opts = parse_args(sys.argv[1:_idx])
+    if "--" in main_args:
+        _idx = main_args.index("--")
+        _argv = main_args[(_idx + 1) :]
+        opts = parse_args(main_args[1:_idx])
         argv = _argv
     else:
-        if "-h" in sys.argv or "--help" in sys.argv:
+        if "-h" in main_args or "--help" in main_args:
             opts = parse_args()
         else:
-            argv = sys.argv[1:]
+            argv = main_args[1:]
             opts = parse_args([])
             if len(argv) == 0 or not os.path.isfile(argv[0]):
                 raise RuntimeError(
-                    "Could not determine input script. Use '--' before "
+                    "Could not determine input script in '{}'. Use '--' before "
                     "the script and its arguments to ensure correct parsing. \nE.g. "
-                    "python -m omnitrace -- ./script.py"
+                    "python -m omnitrace -- ./script.py".format(" ".join(argv))
                 )
 
     if len(argv) > 1:
@@ -337,7 +337,7 @@ def main():
 
     print("[omnitrace]> profiling: {}".format(argv))
 
-    sys.argv[:] = argv
+    main_args[:] = argv
     if opts.setup is not None:
         # Run some setup code outside of the profiler. This is good for large
         # imports.
@@ -351,12 +351,14 @@ def main():
 
     from . import Profiler, FakeProfiler
 
-    script_file = find_script(sys.argv[0])
+    script_file = find_script(main_args[0])
     __file__ = script_file
     __name__ = "__main__"
     # Make sure the script's directory is on sys.path
     sys.path.insert(0, os.path.dirname(script_file))
 
+    _OMNITRACE_PYTHON_SCRIPT_FILE = script_file
+
     prof = Profiler()
     fake = FakeProfiler()
 
@@ -394,7 +396,12 @@ def main():
 
 
 if __name__ == "__main__":
-    main()
+    args = sys.argv
+    if "--" not in args and _OMNITRACE_PYTHON_SCRIPT_FILE is not None:
+        args = [args[0]] + ["--", _OMNITRACE_PYTHON_SCRIPT_FILE] + args[1:]
+        os.environ["OMNITRACE_USE_PID"] = "ON"
+
+    main(args)
     from .libpyomnitrace import finalize
 
     finalize()