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[3.10] bpo-43933: Force RETURN_VALUE bytecodes to have line numbers #26061

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Merged
markshannon merged 3 commits into from
May 13, 2021
Merged

[3.10] bpo-43933: Force RETURN_VALUE bytecodes to have line numbers #26061

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23a5a31
Guarantee that line number is set for returns.
markshannon May 12, 2021
b89dd60
Add test for linenumber of return in nested try statements.
markshannon May 10, 2021
2a34a68
Remove misleading comment
markshannon May 12, 2021
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Guarantee that line number is set for returns.
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@markshannon
markshannon committed May 12, 2021
commit 23a5a31d6f7fdc5bd2497dbdb50cdeba7ee2cc57
1 change: 1 addition & 0 deletions Lib/test/test_sys_settrace.py
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Expand Up @@ -1647,6 +1647,7 @@ async def test_no_jump_forwards_into_async_for_block(output):
output.append(1)
async for i in asynciter([1, 2]):
output.append(3)
pass

@jump_test(3, 2, [2, 2], (ValueError, 'into'))
def test_no_jump_backwards_into_for_block(output):
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31 changes: 31 additions & 0 deletions Python/compile.c
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Expand Up @@ -6960,6 +6960,36 @@ insert_generator_prefix(struct compiler *c, basicblock *entryblock) {
return 0;
}

/* Make sure that all returns have a line number, even if early passes
* have failed to propagate a correct line number.
* The resulting line number may not be correct according to PEP 626,
* but should be "good enough", and no worse than in older versions. */
static void
guarantee_lineno_for_exits(struct assembler *a, int firstlineno) {
int lineno = firstlineno;
assert(lineno > 0);
for (basicblock *b = a->a_entry; b != NULL; b = b->b_next) {
if (b->b_iused == 0) {
continue;
}
struct instr *last = &b->b_instr[b->b_iused-1];
if (last->i_lineno < 0) {
/* A return in a block by itself can't have a linenumber, or
* we can mess up frame.setlineno */
if (last->i_opcode == RETURN_VALUE)
{
for (int i = 0; i < b->b_iused; i++) {
assert(b->b_instr[i].i_lineno < 0);
b->b_instr[i].i_lineno = lineno;
}
}
}
else {
lineno = last->i_lineno;
}
}
}

static PyCodeObject *
assemble(struct compiler *c, int addNone)
{
Expand Down Expand Up @@ -7022,6 +7052,7 @@ assemble(struct compiler *c, int addNone)
if (optimize_cfg(c, &a, consts)) {
goto error;
}
guarantee_lineno_for_exits(&a, c->u->u_firstlineno);

/* Can't modify the bytecode after computing jump offsets. */
assemble_jump_offsets(&a, c);
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