[lldb] [Python] Do not attempt to flush() a read-only fd

Summary:
When creating a FileSP object, do not flush() the underlying file unless
it is open for writing.  Attempting to flush() a read-only fd results
in EBADF on NetBSD.

Reviewers: lawrence_danna, labath, krytarowski

Reviewed By: lawrence_danna, labath

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D69320

1 files changed, 7 insertions, 5 deletions

diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp b/lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
index 70d93424fde..2b85ebf18c6 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp
@@ -1385,11 +1385,13 @@ llvm::Expected<FileSP> PythonFile::ConvertToFile(bool borrowed) {
   if (!options)
     return options.takeError();
 
-  // LLDB and python will not share I/O buffers.  We should probably
-  // flush the python buffers now.
-  auto r = CallMethod("flush");
-  if (!r)
-    return r.takeError();
+  if (options.get() & File::eOpenOptionWrite) {
+    // LLDB and python will not share I/O buffers.  We should probably
+    // flush the python buffers now.
+    auto r = CallMethod("flush");
+    if (!r)
+      return r.takeError();
+  }
 
   FileSP file_sp;
   if (borrowed) {