bpo-42739: Don't use sentinels to mark end of line table. (GH-25657)

* Add length parameter to PyLineTable_InitAddressRange and doen't use sentinel values at end of table. Makes the line number table more robust.

* Update PyCodeAddressRange to match PEP 626.

1 files changed, 8 insertions, 3 deletions

diff --git a/Include/cpython/code.h b/Include/cpython/code.h
index c3065bb..e810eb4 100644
--- a/Include/cpython/code.h
+++ b/Include/cpython/code.h
@@ -135,12 +135,17 @@ PyCode_NewEmpty(const char *filename, const char *funcname, int firstlineno);
 PyAPI_FUNC(int) PyCode_Addr2Line(PyCodeObject *, int);
 
 /* for internal use only */
+struct _opaque {
+    int computed_line;
+    char *lo_next;
+    char *limit;
+};
+
 typedef struct _line_offsets {
     int ar_start;
     int ar_end;
     int ar_line;
-    int ar_computed_line;
-    char *lo_next;
+    struct _opaque opaque;
 } PyCodeAddressRange;
 
 /* Update *bounds to describe the first and one-past-the-last instructions in the
@@ -170,7 +175,7 @@ PyAPI_FUNC(int) _PyCode_SetExtra(PyObject *code, Py_ssize_t index,
 int _PyCode_InitAddressRange(PyCodeObject* co, PyCodeAddressRange *bounds);
 
 /** Out of process API for initializing the line number table. */
-void PyLineTable_InitAddressRange(char *linetable, int firstlineno, PyCodeAddressRange *range);
+void PyLineTable_InitAddressRange(char *linetable, Py_ssize_t length, int firstlineno, PyCodeAddressRange *range);
 
 /** API for traversing the line number table. */
 int PyLineTable_NextAddressRange(PyCodeAddressRange *range);