bpo-42246: Partial implementation of PEP 626. (GH-23113)

* Implement new line number table format, as defined in PEP 626.

1 files changed, 8 insertions, 25 deletions

diff --git a/Lib/dis.py b/Lib/dis.py
index e289e17..ea50f56 100644
--- a/Lib/dis.py
+++ b/Lib/dis.py
@@ -449,32 +449,15 @@ def findlabels(code):
 def findlinestarts(code):
     """Find the offsets in a byte code which are start of lines in the source.
 
-    Generate pairs (offset, lineno) as described in Python/compile.c.
-
+    Generate pairs (offset, lineno)
     """
-    byte_increments = code.co_lnotab[0::2]
-    line_increments = code.co_lnotab[1::2]
-    bytecode_len = len(code.co_code)
-
-    lastlineno = None
-    lineno = code.co_firstlineno
-    addr = 0
-    for byte_incr, line_incr in zip(byte_increments, line_increments):
-        if byte_incr:
-            if lineno != lastlineno:
-                yield (addr, lineno)
-                lastlineno = lineno
-            addr += byte_incr
-            if addr >= bytecode_len:
-                # The rest of the lnotab byte offsets are past the end of
-                # the bytecode, so the lines were optimized away.
-                return
-        if line_incr >= 0x80:
-            # line_increments is an array of 8-bit signed integers
-            line_incr -= 0x100
-        lineno += line_incr
-    if lineno != lastlineno:
-        yield (addr, lineno)
+    lastline = None
+    for start, end, line in code.co_lines():
+        if line is not None and line != lastline:
+            lastline = line
+            yield start, line
+    return
+
 
 class Bytecode:
     """The bytecode operations of a piece of code