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.
diff --git a/Objects/codeobject.c b/Objects/codeobject.c
index 9bb49f1..c76ac90 100644
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -456,15 +456,15 @@ code_getlnotab(PyCodeObject *code, void *closure)
}
_PyCode_InitAddressRange(code, &bounds);
while (PyLineTable_NextAddressRange(&bounds)) {
- if (bounds.ar_computed_line != line) {
+ if (bounds.opaque.computed_line != line) {
int bdelta = bounds.ar_start - code_offset;
- int ldelta = bounds.ar_computed_line - line;
+ int ldelta = bounds.opaque.computed_line - line;
if (!emit_delta(&bytes, bdelta, ldelta, &table_offset)) {
Py_DECREF(bytes);
return NULL;
}
code_offset = bounds.ar_start;
- line = bounds.ar_computed_line;
+ line = bounds.opaque.computed_line;
}
}
_PyBytes_Resize(&bytes, table_offset);
@@ -1120,20 +1120,20 @@ code_linesiterator(PyCodeObject *code, PyObject *Py_UNUSED(args))
static void
retreat(PyCodeAddressRange *bounds)
{
- int ldelta = ((signed char *)bounds->lo_next)[-1];
+ int ldelta = ((signed char *)bounds->opaque.lo_next)[-1];
if (ldelta == -128) {
ldelta = 0;
}
- bounds->ar_computed_line -= ldelta;
- bounds->lo_next -= 2;
+ bounds->opaque.computed_line -= ldelta;
+ bounds->opaque.lo_next -= 2;
bounds->ar_end = bounds->ar_start;
- bounds->ar_start -= ((unsigned char *)bounds->lo_next)[-2];
- ldelta = ((signed char *)bounds->lo_next)[-1];
+ bounds->ar_start -= ((unsigned char *)bounds->opaque.lo_next)[-2];
+ ldelta = ((signed char *)bounds->opaque.lo_next)[-1];
if (ldelta == -128) {
bounds->ar_line = -1;
}
else {
- bounds->ar_line = bounds->ar_computed_line;
+ bounds->ar_line = bounds->opaque.computed_line;
}
}
@@ -1141,23 +1141,22 @@ static void
advance(PyCodeAddressRange *bounds)
{
bounds->ar_start = bounds->ar_end;
- int delta = ((unsigned char *)bounds->lo_next)[0];
- assert (delta < 255);
+ int delta = ((unsigned char *)bounds->opaque.lo_next)[0];
bounds->ar_end += delta;
- int ldelta = ((signed char *)bounds->lo_next)[1];
- bounds->lo_next += 2;
+ int ldelta = ((signed char *)bounds->opaque.lo_next)[1];
+ bounds->opaque.lo_next += 2;
if (ldelta == -128) {
bounds->ar_line = -1;
}
else {
- bounds->ar_computed_line += ldelta;
- bounds->ar_line = bounds->ar_computed_line;
+ bounds->opaque.computed_line += ldelta;
+ bounds->ar_line = bounds->opaque.computed_line;
}
}
static inline int
at_end(PyCodeAddressRange *bounds) {
- return ((unsigned char *)bounds->lo_next)[0] == 255;
+ return bounds->opaque.lo_next >= bounds->opaque.limit;
}
int
@@ -1256,12 +1255,13 @@ PyCode_Addr2Line(PyCodeObject *co, int addrq)
}
void
-PyLineTable_InitAddressRange(char *linetable, int firstlineno, PyCodeAddressRange *range)
+PyLineTable_InitAddressRange(char *linetable, Py_ssize_t length, int firstlineno, PyCodeAddressRange *range)
{
- range->lo_next = linetable;
+ range->opaque.lo_next = linetable;
+ range->opaque.limit = range->opaque.lo_next + length;
range->ar_start = -1;
range->ar_end = 0;
- range->ar_computed_line = firstlineno;
+ range->opaque.computed_line = firstlineno;
range->ar_line = -1;
}
@@ -1269,7 +1269,8 @@ int
_PyCode_InitAddressRange(PyCodeObject* co, PyCodeAddressRange *bounds)
{
char *linetable = PyBytes_AS_STRING(co->co_linetable);
- PyLineTable_InitAddressRange(linetable, co->co_firstlineno, bounds);
+ Py_ssize_t length = PyBytes_GET_SIZE(co->co_linetable);
+ PyLineTable_InitAddressRange(linetable, length, co->co_firstlineno, bounds);
return bounds->ar_line;
}
diff --git a/Objects/lnotab_notes.txt b/Objects/lnotab_notes.txt
index 59c6525..f482310 100644
--- a/Objects/lnotab_notes.txt
+++ b/Objects/lnotab_notes.txt
@@ -39,7 +39,6 @@
Finally, in order to fit into a single byte we need to convert start deltas to the range 0 <= delta <= 254,
and line deltas to the range -127 <= delta <= 127.
A line delta of -128 is used to indicate no line number.
-A start delta of 255 is used as a sentinel to mark the end of the table.
Also note that a delta of zero indicates that there are no bytecodes in the given range,
which means we can use an invalid line number for that range.
@@ -54,7 +53,6 @@
16 +1
0 +127 (line 135, but the range is empty as no bytecodes are at line 135)
4 +73
- 255 (end mark) ---
Iterating over the table.
-------------------------
@@ -68,8 +66,6 @@
end = 0
table_iter = iter(code.internal_line_table):
for sdelta, ldelta in table_iter:
- if sdelta == 255:
- break
if ldelta == 0: # No change to line number, just accumulate changes to end
end += odelta
continue