Fixed an issue where python would always use stdin, stdout and stderr

[clayborg]

Summary

After the Python 3 fixes the interactive python interpreter stopped working in Xcode. The issue was the python interpreter tried to adopt the top IOHandler file handles, but it failed due to lldb_private::File objects failing to copy themselves into another lldb_private::File because they contained "FILE *" file stream pointer, not just an integer file descriptor, and File::Duplicate() didn't handle duplicating "FILE *". But we really don't want files duplicating themselves each time we run a python expression, we just want to use the files.

The fix involves removing File::Duplicate() since we shouldn't be using this and duplicating files. It also removes File's assignment operator and copy constructor. It then fixes the python interpreter to correctly adopt the file handles from the top IOHandler.

[zturner]

Looks good, and it doesn't break anything on Windows. Glad we got rid of copying and duplication, that always seemed like unnecessary complexity.

[clayborg]

Submitted with SVN revision 263161.

include/lldb/Host/File.h

     {
     }
 
-    File (const File &rhs);
-    
     //------------------------------------------------------------------
     /// Constructor with path.
     ///

     //------------------------------------------------------------------
     ~File() override;
 
-    File &
-    operator= (const File &rhs);
-
     bool
     IsValid() const override
     {

     void
     Clear ();
     
-    Error
-    Duplicate (const File &rhs);
-
     int
     GetDescriptor() const;
 

     LazyBool m_is_interactive;
     LazyBool m_is_real_terminal;
     LazyBool m_supports_colors;
+
+private:
+    DISALLOW_COPY_AND_ASSIGN(File);
 };
 
 } // namespace lldb_private

source/Host/common/File.cpp

     }
 }
 
-File::File (const File &rhs) :
-    IOObject(eFDTypeFile, false),
-    m_descriptor (kInvalidDescriptor),
-    m_stream (kInvalidStream),
-    m_options (0),
-    m_own_stream (false),
-    m_is_interactive (eLazyBoolCalculate),
-    m_is_real_terminal (eLazyBoolCalculate)
-{
-    Duplicate (rhs);
-}
-    
-
-File &
-File::operator = (const File &rhs)
-{
-    if (this != &rhs)
-        Duplicate (rhs);        
-    return *this;
-}
-
 File::~File()
 {
     Close ();

     return m_stream;
 }
 
-
 void
 File::SetStream (FILE *fh, bool transfer_ownership)
 {

 }
 
 Error
-File::Duplicate (const File &rhs)
-{
-    Error error;
-    if (IsValid ())
-        Close();
-
-    if (rhs.DescriptorIsValid())
-    {
-#ifdef _WIN32
-        m_descriptor = ::_dup(rhs.GetDescriptor());
-#else
-        m_descriptor = dup(rhs.GetDescriptor());
-#endif
-        if (!DescriptorIsValid())
-            error.SetErrorToErrno();
-        else
-        {
-            m_options = rhs.m_options;
-            m_should_close_fd = true;
-        }
-    }
-    else
-    {
-        error.SetErrorString ("invalid file to duplicate");
-    }
-    return error;
-}
-
-Error
 File::Open (const char *path, uint32_t options, uint32_t permissions)
 {
     Error error;

source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.h

     bool
     GetEmbeddedInterpreterModuleObjects ();
 
+    bool
+    SetStdHandle(File &file, const char *py_name, PythonFile &save_file, const char *mode);
+
     PythonFile m_saved_stdin;
     PythonFile m_saved_stdout;
     PythonFile m_saved_stderr;

source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp

 }
 
 bool
+ScriptInterpreterPython::SetStdHandle(File &file, const char *py_name, PythonFile &save_file, const char *mode)
+{
+    if (file.IsValid())
+    {
+        // Flush the file before giving it to python to avoid interleaved output.
+        file.Flush();
+
+        PythonDictionary &sys_module_dict = GetSysModuleDictionary();
+
+        save_file = sys_module_dict.GetItemForKey(PythonString(py_name)).AsType<PythonFile>();
+
+        PythonFile new_file(file, mode);
+        sys_module_dict.SetItemForKey(PythonString(py_name), new_file);
+        return true;
+    }
+    else
+        save_file.Reset();
+    return false;
+}
+
+bool
 ScriptInterpreterPython::EnterSession (uint16_t on_entry_flags,
                                        FILE *in,
                                        FILE *out,

         if (!in_file.IsValid() || !out_file.IsValid() || !err_file.IsValid())
             m_interpreter.GetDebugger().AdoptTopIOHandlerFilesIfInvalid (in_sp, out_sp, err_sp);
 
-        m_saved_stdin.Reset();
 
-        if ((on_entry_flags & Locker::NoSTDIN) == 0)
+        if (on_entry_flags & Locker::NoSTDIN)
         {
-            // STDIN is enabled
-            if (!in_file.IsValid() && in_sp)
-                in_file = in_sp->GetFile();
-            if (in_file.IsValid())
+            m_saved_stdin.Reset();
+        }
+        else
+        {
+            if (!SetStdHandle(in_file, "stdin", m_saved_stdin, "r"))
             {
-                // Flush the file before giving it to python to avoid interleaved output.
-                in_file.Flush();
-
-                m_saved_stdin = sys_module_dict.GetItemForKey(PythonString("stdin")).AsType<PythonFile>();
-                // This call can deadlock your process if the file is locked
-                PythonFile new_file(in_file, "r");
-                sys_module_dict.SetItemForKey (PythonString("stdin"), new_file);
+                if (in_sp)
+                    SetStdHandle(in_sp->GetFile(), "stdin", m_saved_stdin, "r");
             }
         }
 
-        if (!out_file.IsValid() && out_sp)
-            out_file = out_sp->GetFile();
-        if (out_file.IsValid())
+        if (!SetStdHandle(out_file, "stdout", m_saved_stdout, "w"))
         {
-            // Flush the file before giving it to python to avoid interleaved output.
-            out_file.Flush();
-
-            m_saved_stdout = sys_module_dict.GetItemForKey(PythonString("stdout")).AsType<PythonFile>();
-
-            PythonFile new_file(out_file, "w");
-            sys_module_dict.SetItemForKey (PythonString("stdout"), new_file);
+            if (out_sp)
+                SetStdHandle(out_sp->GetFile(), "stdout", m_saved_stdout, "w");
         }
-        else
-            m_saved_stdout.Reset();
 
-        if (!err_file.IsValid() && err_sp)
-            err_file = err_sp->GetFile();
-        if (err_file.IsValid())
+        if (!SetStdHandle(err_file, "stderr", m_saved_stderr, "w"))
         {
-            // Flush the file before giving it to python to avoid interleaved output.
-            err_file.Flush();
-
-            m_saved_stderr = sys_module_dict.GetItemForKey(PythonString("stderr")).AsType<PythonFile>();
-
-            PythonFile new_file(err_file, "w");
-            sys_module_dict.SetItemForKey (PythonString("stderr"), new_file);
+            if (err_sp)
+                SetStdHandle(err_sp->GetFile(), "stderr", m_saved_stderr, "w");
         }
-        else
-            m_saved_stderr.Reset();
     }
 
     if (PyErr_Occurred())