Issue #6042:
lnotab-based tracing is very complicated and isn't documented very well. There
were at least 3 comment blocks purporting to document co_lnotab, and none did a
very good job. This patch unifies them into Objects/lnotab_notes.txt which
tries to completely capture the current state of affairs.
I also discovered that we've attached 2 layers of patches to the basic tracing
scheme. The first layer avoids jumping to instructions that don't start a line,
to avoid problems in if statements and while loops. The second layer
discovered that jumps backward do need to trace at instructions that don't
start a line, so it added extra lnotab entries for 'while' and 'for' loops, and
added a special case for backward jumps within the same line. I replaced these
patches by just treating forward and backward jumps differently.
diff --git a/Include/code.h b/Include/code.h
index cbf00d8..260c5f0 100644
--- a/Include/code.h
+++ b/Include/code.h
@@ -23,7 +23,8 @@
PyObject *co_filename; /* string (where it was loaded from) */
PyObject *co_name; /* string (name, for reference) */
int co_firstlineno; /* first source line number */
- PyObject *co_lnotab; /* string (encoding addr<->lineno mapping) */
+ PyObject *co_lnotab; /* string (encoding addr<->lineno mapping) See
+ Objects/lnotab_notes.txt for details. */
void *co_zombieframe; /* for optimization only (see frameobject.c) */
} PyCodeObject;
@@ -90,15 +91,11 @@
int ap_upper;
} PyAddrPair;
-/* Check whether lasti (an instruction offset) falls outside bounds
- and whether it is a line number that should be traced. Returns
- a line number if it should be traced or -1 if the line should not.
-
- If lasti is not within bounds, updates bounds.
+/* Update *bounds to describe the first and one-past-the-last instructions in the
+ same line as lasti. Return the number of that line.
*/
-
-PyAPI_FUNC(int) PyCode_CheckLineNumber(PyCodeObject* co,
- int lasti, PyAddrPair *bounds);
+PyAPI_FUNC(int) _PyCode_CheckLineNumber(PyCodeObject* co,
+ int lasti, PyAddrPair *bounds);
PyAPI_FUNC(PyObject*) PyCode_Optimize(PyObject *code, PyObject* consts,
PyObject *names, PyObject *lineno_obj);