co_lnotab supports negative line number delta
Issue #26107: The format of the co_lnotab attribute of code objects changes to
support negative line number delta.
Changes:
* assemble_lnotab(): if line number delta is less than -128 or greater than
127, emit multiple (offset_delta, lineno_delta) in co_lnotab
* update functions decoding co_lnotab to use signed 8-bit integers
- dis.findlinestarts()
- PyCode_Addr2Line()
- _PyCode_CheckLineNumber()
- frame_setlineno()
* update lnotab_notes.txt
* increase importlib MAGIC_NUMBER to 3361
* document the change in What's New in Python 3.6
* cleanup also PyCode_Optimize() to use better variable names
diff --git a/Python/compile.c b/Python/compile.c
index 0f619c4..f362ac6 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -4452,7 +4452,6 @@
d_lineno = i->i_lineno - a->a_lineno;
assert(d_bytecode >= 0);
- assert(d_lineno >= 0);
if(d_bytecode == 0 && d_lineno == 0)
return 1;
@@ -4482,9 +4481,21 @@
d_bytecode -= ncodes * 255;
a->a_lnotab_off += ncodes * 2;
}
- assert(d_bytecode <= 255);
- if (d_lineno > 255) {
- int j, nbytes, ncodes = d_lineno / 255;
+ assert(0 <= d_bytecode && d_bytecode <= 255);
+
+ if (d_lineno < -128 || 127 < d_lineno) {
+ int j, nbytes, ncodes, k;
+ if (d_lineno < 0) {
+ k = -128;
+ /* use division on positive numbers */
+ ncodes = (-d_lineno) / 128;
+ }
+ else {
+ k = 127;
+ ncodes = d_lineno / 127;
+ }
+ d_lineno -= ncodes * k;
+ assert(ncodes >= 1);
nbytes = a->a_lnotab_off + 2 * ncodes;
len = PyBytes_GET_SIZE(a->a_lnotab);
if (nbytes >= len) {
@@ -4502,15 +4513,15 @@
lnotab = (unsigned char *)
PyBytes_AS_STRING(a->a_lnotab) + a->a_lnotab_off;
*lnotab++ = d_bytecode;
- *lnotab++ = 255;
+ *lnotab++ = k;
d_bytecode = 0;
for (j = 1; j < ncodes; j++) {
*lnotab++ = 0;
- *lnotab++ = 255;
+ *lnotab++ = k;
}
- d_lineno -= ncodes * 255;
a->a_lnotab_off += ncodes * 2;
}
+ assert(-128 <= d_lineno && d_lineno <= 127);
len = PyBytes_GET_SIZE(a->a_lnotab);
if (a->a_lnotab_off + 2 >= len) {