Issue 5954, PyFrame_GetLineNumber:

Most uses of PyCode_Addr2Line
(http://www.google.com/codesearch?q=PyCode_Addr2Line) are just trying to get
the line number of a specified frame, but there's no way to do that directly.
Forcing people to go through the code object makes them know more about the
guts of the interpreter than they should need.

The remaining uses of PyCode_Addr2Line seem to be getting the line from a
traceback (for example,
http://www.google.com/codesearch/p?hl=en#u_9_nDrchrw/pygame-1.7.1release/src/base.c&q=PyCode_Addr2Line),
which is replaced by the tb_lineno field.  So we may be able to deprecate
PyCode_Addr2Line entirely for external use.

8 files changed, 35 insertions, 19 deletions

diff --git a/Doc/c-api/reflection.rst b/Doc/c-api/reflection.rst
index 822c593..3996c1f 100644
--- a/Doc/c-api/reflection.rst
+++ b/Doc/c-api/reflection.rst
@@ -29,6 +29,11 @@ Reflection
    currently executing.
 
 
+.. cfunction:: int PyFrame_GetLineNumber(PyFrameObject *frame)
+
+   Return the line number that *frame* is currently executing.
+
+
 .. cfunction:: int PyEval_GetRestricted()
 
    If there is a current frame and it is executing in restricted mode, return true,
diff --git a/Include/code.h b/Include/code.h
index 0167ad4..cbf00d8 100644
--- a/Include/code.h
+++ b/Include/code.h
@@ -75,6 +75,9 @@ PyAPI_FUNC(PyCodeObject *) PyCode_New(
 PyAPI_FUNC(PyCodeObject *)
 PyCode_NewEmpty(const char *filename, const char *funcname, int firstlineno);
 
+/* Return the line number associated with the specified bytecode index
+   in this code object.  If you just need the line number of a frame,
+   use PyFrame_GetLineNumber() instead. */
 PyAPI_FUNC(int) PyCode_Addr2Line(PyCodeObject *, int);
 
 /* for internal use only */
diff --git a/Include/frameobject.h b/Include/frameobject.h
index 297b66d..17e7679 100644
--- a/Include/frameobject.h
+++ b/Include/frameobject.h
@@ -38,8 +38,11 @@ typedef struct _frame {
 
     PyThreadState *f_tstate;
     int f_lasti;		/* Last instruction if called */
-    /* As of 2.3 f_lineno is only valid when tracing is active (i.e. when
-       f_trace is set) -- at other times use PyCode_Addr2Line instead. */
+    /* Call PyFrame_GetLineNumber() instead of reading this field
+       directly.  As of 2.3 f_lineno is only valid when tracing is
+       active (i.e. when f_trace is set).  At other times we use
+       PyCode_Addr2Line to calculate the line from the current
+       bytecode index. */
     int f_lineno;		/* Current line number */
     int f_iblock;		/* index in f_blockstack */
     PyTryBlock f_blockstack[CO_MAXBLOCKS]; /* for try and loop blocks */
@@ -77,6 +80,9 @@ PyAPI_FUNC(void) PyFrame_FastToLocals(PyFrameObject *);
 
 PyAPI_FUNC(int) PyFrame_ClearFreeList(void);
 
+/* Return the line of code the frame is currently executing. */
+PyAPI_FUNC(int) PyFrame_GetLineNumber(PyFrameObject *);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Misc/NEWS b/Misc/NEWS
index ba721e7..fa362fd 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -927,6 +927,9 @@ Build
 C-API
 -----
 
+- Issue #5954: Add a PyFrame_GetLineNumber() function to replace most uses of
+  PyCode_Addr2Line().
+
 - Issue #5959: Add a PyCode_NewEmpty() function to create a new empty code
   object at a specified file, function, and line number.
 
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 4ac1ab0..7a9d40d 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -60,17 +60,19 @@ frame_getlocals(PyFrameObject *f, void *closure)
 	return f->f_locals;
 }
 
-static PyObject *
-frame_getlineno(PyFrameObject *f, void *closure)
+int
+PyFrame_GetLineNumber(PyFrameObject *f)
 {
-	int lineno;
-
 	if (f->f_trace)
-		lineno = f->f_lineno;
+		return f->f_lineno;
 	else
-		lineno = PyCode_Addr2Line(f->f_code, f->f_lasti);
+		return PyCode_Addr2Line(f->f_code, f->f_lasti);
+}
 
-	return PyInt_FromLong(lineno);
+static PyObject *
+frame_getlineno(PyFrameObject *f, void *closure)
+{
+	return PyInt_FromLong(PyFrame_GetLineNumber(f));
 }
 
 /* Setter for f_lineno - you can set f_lineno from within a trace function in
@@ -351,16 +353,14 @@ frame_gettrace(PyFrameObject *f, void *closure)
 static int
 frame_settrace(PyFrameObject *f, PyObject* v, void *closure)
 {
-	/* We rely on f_lineno being accurate when f_trace is set. */
+	PyObject* old_value;
 
-	PyObject* old_value = f->f_trace;
+	/* We rely on f_lineno being accurate when f_trace is set. */
+	f->f_lineno = PyFrame_GetLineNumber(f);
 
+	old_value = f->f_trace;
 	Py_XINCREF(v);
 	f->f_trace = v;
-
-	if (v != NULL)
-		f->f_lineno = PyCode_Addr2Line(f->f_code, f->f_lasti);
-
 	Py_XDECREF(old_value);
 
 	return 0;
diff --git a/Python/_warnings.c b/Python/_warnings.c
index 1a7c2d5..219cfc6 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -454,7 +454,7 @@ setup_context(Py_ssize_t stack_level, PyObject **filename, int *lineno,
     }
     else {
         globals = f->f_globals;
-        *lineno = PyCode_Addr2Line(f->f_code, f->f_lasti);
+        *lineno = PyFrame_GetLineNumber(f);
     }
 
     *module = NULL;
diff --git a/Python/ceval.c b/Python/ceval.c
index 88b9d0e..474a885 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2698,7 +2698,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
 		default:
 			fprintf(stderr,
 				"XXX lineno: %d, opcode: %d\n",
-				PyCode_Addr2Line(f->f_code, f->f_lasti),
+				PyFrame_GetLineNumber(f),
 				opcode);
 			PyErr_SetString(PyExc_SystemError, "unknown opcode");
 			why = WHY_EXCEPTION;
diff --git a/Python/traceback.c b/Python/traceback.c
index c2d7e77..1c26ba2 100644
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -96,8 +96,7 @@ newtracebackobject(PyTracebackObject *next, PyFrameObject *frame)
 		Py_XINCREF(frame);
 		tb->tb_frame = frame;
 		tb->tb_lasti = frame->f_lasti;
-		tb->tb_lineno = PyCode_Addr2Line(frame->f_code, 
-						 frame->f_lasti);
+		tb->tb_lineno = PyFrame_GetLineNumber(frame);
 		PyObject_GC_Track(tb);
 	}
 	return tb;