[Lldb-commits] [PATCH] D69532: [LLDB][PythonFile] fix dangerous borrow semantics on python2

[Lawrence D'Anna via Phabricator via lldb-commits]

lawrence_danna updated this revision to Diff 227007.
lawrence_danna added a comment.

just don't even flush


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D69532/new/

https://reviews.llvm.org/D69532

Files:
  lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp


Index: lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
===================================================================
--- lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
+++ lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
@@ -1500,21 +1500,23 @@
   PyObject *file_obj;
 #if PY_MAJOR_VERSION >= 3
   file_obj = PyFile_FromFd(file.GetDescriptor(), nullptr, mode, -1, nullptr,
-                           "ignore", nullptr, 0);
+                           "ignore", nullptr, /*closefd=*/0);
 #else
-  // We pass ::flush instead of ::fclose here so we borrow the FILE* --
-  // the lldb_private::File still owns it.   NetBSD does not allow
-  // input files to be flushed, so we have to check for that case too.
-  int (*closer)(FILE *);
-  auto opts = file.GetOptions();
-  if (!opts)
-    return opts.takeError();
-  if (opts.get() & File::eOpenOptionWrite)
-    closer = ::fflush;
-  else
-    closer = [](FILE *) { return 0; };
+  // I'd like to pass ::fflush here if the file is writable,  so that
+  // when the python side destructs the file object it will be flushed.
+  // However, this would be dangerous.    It can cause fflush to be called
+  // after fclose if the python program keeps a reference to the file after
+  // the original lldb_private::File has been destructed.
+  //
+  // It's all well and good to ask a python program not to use a closed file
+  // but asking a python program to make sure objects get released in a
+  // particular order is not safe.
+  //
+  // The tradeoff here is that if a python 2 program wants to make sure this
+  // file gets flushed, they'll have to do it explicitly or wait untill the
+  // original lldb File itself gets flushed.
   file_obj = PyFile_FromFile(file.GetStream(), py2_const_cast(""),
-                             py2_const_cast(mode), closer);
+                             py2_const_cast(mode), [](FILE *) { return 0; });
 #endif
 
   if (!file_obj)


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