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gh-107901: Fix missing line number on BACKWARD_JUMP at the end of a for loop #108242

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Merged
merged 2 commits into from
Aug 21, 2023
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gh-107901: Fix missing line number on BACKWARD_JUMP at the end of a for loop #108242

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5d4b31f
Fix missing line number on :opcode:`BACKWARD_JUMP` at the end of a fo…
iritkatriel Aug 21, 2023
4c65946
backward
iritkatriel Aug 21, 2023
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14 changes: 14 additions & 0 deletions Lib/test/test_compile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1031,6 +1031,20 @@ async def test(aseq):
code_lines = self.get_code_lines(test.__code__)
self.assertEqual(expected_lines, code_lines)

def test_lineno_of_backward_jump(self):
# Issue gh-107901
def f():
for i in x:
if y:
pass

linenos = list(inst.positions.lineno
for inst in dis.get_instructions(f.__code__)
if inst.opname == 'JUMP_BACKWARD')

self.assertTrue(len(linenos) > 0)
self.assertTrue(all(l is not None for l in linenos))

def test_big_dict_literal(self):
# The compiler has a flushing point in "compiler_dict" that calls compiles
# a portion of the dictionary literal when the loop that iterates over the items
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2023-08-21-21-13-30.gh-issue-107901.hszvdk.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix missing line number on :opcode:`JUMP_BACKWARD` at the end of a for loop.
2 changes: 1 addition & 1 deletion Python/flowgraph.c
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Expand Up @@ -531,7 +531,7 @@ normalize_jumps_in_block(cfg_builder *g, basicblock *b) {
if (backwards_jump == NULL) {
return ERROR;
}
basicblock_addop(backwards_jump, JUMP, target->b_label.id, NO_LOCATION);
basicblock_addop(backwards_jump, JUMP, target->b_label.id, last->i_loc);
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This is the last physical location, not the last location executed. Won't it give the wrong line for the following?

ALWAYS_TRUE= True

def foo():
    while 1:
        if ALWAYS_TRUE:
            pass # last line executed
        else:
            pass # last physical line

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@iritkatriel iritkatriel Aug 22, 2023 •
edited
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no, last is the conditional backwards jump that this jump is replacing (and which is replaced by a forward jump).

backwards_jump->b_instr[0].i_target = target;
last->i_opcode = reversed_opcode;
last->i_target = b->b_next;
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