From c8de17bca658e62bbf8c33eae839e457332e885e Mon Sep 17 00:00:00 2001
From: Lawrence D'Anna <lawrence_danna@apple.com>
Date: Tue, 7 Apr 2020 13:29:58 -0700
Subject: [PATCH] Fix illegal early call to PyBuffer_Release in swig typemaps

Summary:
The buffer protocol does not allow us to just call PyBuffer_Release
and assume the buffer will still be there.   Most things that implement the
buffer protocol will let us get away with that, but not all.   We need
to release it at the end of the SWIG wrapper.

Reviewers: labath, jasonmolenda, JDevlieghere, vadimcn

Reviewed By: labath

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D77480
---
 lldb/bindings/python/python-typemaps.swig | 38 +++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/lldb/bindings/python/python-typemaps.swig b/lldb/bindings/python/python-typemaps.swig
index bfd7ef9..46dcaf6 100644
--- a/lldb/bindings/python/python-typemaps.swig
+++ b/lldb/bindings/python/python-typemaps.swig
@@ -488,39 +488,53 @@ bool SetNumberFromPyObject<double>(double &number, PyObject *obj) {
     }
 }
 
+%inline %{
+
+struct Py_buffer_RAII {
+  Py_buffer buffer = {};
+  Py_buffer_RAII() {};
+  Py_buffer &operator=(const Py_buffer_RAII &) = delete;
+  Py_buffer_RAII(const Py_buffer_RAII &) = delete;
+  ~Py_buffer_RAII() {
+    if (buffer.obj)
+      PyBuffer_Release(&buffer);
+  }
+};
+
+%}
+
 // These two pybuffer macros are copied out of swig/Lib/python/pybuffer.i,
 // and fixed so they will not crash if PyObject_GetBuffer fails.
 // https://github.com/swig/swig/issues/1640
+//
+// I've also moved the call to PyBuffer_Release to the end of the SWIG wrapper,
+// doing it right away is not legal according to the python buffer protocol.
 
 %define %pybuffer_mutable_binary(TYPEMAP, SIZE)
-%typemap(in) (TYPEMAP, SIZE) {
+%typemap(in) (TYPEMAP, SIZE) (Py_buffer_RAII view) {
   int res; Py_ssize_t size = 0; void *buf = 0;
-  Py_buffer view;
-  res = PyObject_GetBuffer($input, &view, PyBUF_WRITABLE);
+  res = PyObject_GetBuffer($input, &view.buffer, PyBUF_WRITABLE);
   if (res < 0) {
     PyErr_Clear();
     %argument_fail(res, "(TYPEMAP, SIZE)", $symname, $argnum);
   }
-  size = view.len;
-  buf = view.buf;
-  PyBuffer_Release(&view);
+  size = view.buffer.len;
+  buf = view.buffer.buf;
   $1 = ($1_ltype) buf;
   $2 = ($2_ltype) (size/sizeof($*1_type));
 }
 %enddef
 
 %define %pybuffer_binary(TYPEMAP, SIZE)
-%typemap(in) (TYPEMAP, SIZE) {
+%typemap(in) (TYPEMAP, SIZE) (Py_buffer_RAII view) {
   int res; Py_ssize_t size = 0; const void *buf = 0;
-  Py_buffer view;
-  res = PyObject_GetBuffer($input, &view, PyBUF_CONTIG_RO);
+  res = PyObject_GetBuffer($input, &view.buffer, PyBUF_CONTIG_RO);
   if (res < 0) {
     PyErr_Clear();
     %argument_fail(res, "(TYPEMAP, SIZE)", $symname, $argnum);
   }
-  size = view.len;
-  buf = view.buf;
-  PyBuffer_Release(&view);
+  size = view.buffer.len;
+  buf = view.buffer.buf;
   $1 = ($1_ltype) buf;
   $2 = ($2_ltype) (size / sizeof($*1_type));
 }
-- 
2.7.4