Make C lines in exception tracebacks a runtime setting.

Also changes the default to False.

CHANGES.rst

@@ -24,6 +24,10 @@ Features added
 
 * cdef classes now support pickling by default when possible.
 
+* The display of C lines in Cython tracebacks is now settable at runtime
+  via `import cython_runtime; cython_runtime.cline_in_traceback=True`.
+  The default has been changed to False.
+
 Bugs fixed
 ----------
 

Cython/Compiler/ModuleNode.py

@@ -702,6 +702,7 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
         code.putln('static PyObject *%s;' % env.module_cname)
         code.putln('static PyObject *%s;' % env.module_dict_cname)
         code.putln('static PyObject *%s;' % Naming.builtins_cname)
+        code.putln('static PyObject *%s;' % Naming.cython_runtime_cname)
         code.putln('static PyObject *%s;' % Naming.empty_tuple)
         code.putln('static PyObject *%s;' % Naming.empty_bytes)
         code.putln('static PyObject *%s;' % Naming.empty_unicode)
@@ -2476,6 +2477,10 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
             '%s = PyImport_AddModule(__Pyx_BUILTIN_MODULE_NAME); %s' % (
                 Naming.builtins_cname,
                 code.error_goto_if_null(Naming.builtins_cname, self.pos)))
+        code.putln(
+            '%s = PyImport_AddModule((char *) "cython_runtime"); %s' % (
+                Naming.cython_runtime_cname,
+                code.error_goto_if_null(Naming.cython_runtime_cname, self.pos)))
         code.putln('#if CYTHON_COMPILING_IN_PYPY')
         code.putln('Py_INCREF(%s);' % Naming.builtins_cname)
         code.putln('#endif')

Cython/Compiler/Naming.py

@@ -112,6 +112,7 @@ frame_code_cname = pyrex_prefix + "frame_code"
 binding_cfunc    = pyrex_prefix + "binding_PyCFunctionType"
 fused_func_prefix = pyrex_prefix + 'fuse_'
 quick_temp_cname = pyrex_prefix + "temp" # temp variable for quick'n'dirty temping
+cython_runtime_cname   = pyrex_prefix + "cython_runtime"
 
 global_code_object_cache_find = pyrex_prefix + 'find_code_object'
 global_code_object_cache_insert = pyrex_prefix + 'insert_code_object'

Cython/Utility/Exceptions.c

@@ -600,13 +600,25 @@ static void __Pyx_AddTraceback(const char *funcname, int c_line,
                                int py_line, const char *filename) {
     PyCodeObject *py_code = 0;
     PyFrameObject *py_frame = 0;
+    PyObject *use_cline = 0;
+    PyObject *ptype, *pvalue, *ptraceback;
 
-    py_code = $global_code_object_cache_find(c_line ? c_line : py_line);
+    if (c_line) {
+      PyErr_Fetch(&ptype, &pvalue, &ptraceback);
+      use_cline = PyObject_GetAttrString(${cython_runtime_cname}, "cline_in_traceback");
+      if (use_cline == NULL || PyObject_Not(use_cline) != 0) {
+        c_line = 0;
+      }
+      PyErr_Restore(ptype, pvalue, ptraceback);
+    }
+
+    // Negate to avoid collisions between py and c lines.
+    py_code = $global_code_object_cache_find(c_line ? -c_line : py_line);
     if (!py_code) {
         py_code = __Pyx_CreateCodeObjectForTraceback(
             funcname, c_line, py_line, filename);
         if (!py_code) goto bad;
-        $global_code_object_cache_insert(c_line ? c_line : py_line, py_code);
+        $global_code_object_cache_insert(c_line ? -c_line : py_line, py_code);
     }
     py_frame = PyFrame_New(
         PyThreadState_GET(), /*PyThreadState *tstate,*/
@@ -620,4 +632,5 @@ static void __Pyx_AddTraceback(const char *funcname, int c_line,
 bad:
     Py_XDECREF(py_code);
     Py_XDECREF(py_frame);
+    Py_XDECREF(use_cline);
 }

tests/run/tracebacks.pyx

+import traceback
+
+def foo1():
+  foo2()
+
+cdef foo2():
+  foo3()
+
+cdef int foo3() except -1:
+  raise RuntimeError('my_message')
+
+def test_traceback(cline_in_traceback=None):
+  """
+  >>> test_traceback()
+  >>> test_traceback(True)
+  >>> test_traceback(False)
+  """
+  if cline_in_traceback is not None:
+    import cython_runtime
+    cython_runtime.cline_in_traceback = cline_in_traceback
+  try:
+    foo1()
+  except:
+    tb_string = traceback.format_exc()
+    expected = (
+      'tracebacks.pyx',
+      'foo1', 'foo2', 'foo3',
+      'line 4', 'line 7', 'line 10',
+      'my_message')
+    for s in expected:
+      assert s in tb_string, s
+    if cline_in_traceback:
+      assert 'tracebacks.c' in tb_string
+    else:
+      assert 'tracebacks.c' not in tb_string