Skip to content

Properly fix Jump out of too many nested blocks error #21

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 4 commits into from
Closed

Properly fix Jump out of too many nested blocks error #21

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
c5a1271
Properly fix `Jump out of too many nested blocks` error
insignification Dec 10, 2019
8b431a2
Rename new SyntaxError to be more descriptive in case ever encountered.
Dec 10, 2019
c1613f5
Style & test updates (other updates to commit in following commits)
Dec 13, 2019
df40382
Refactor the ops sizing/writing to avoid code duplication
Dec 13, 2019
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
72 changes: 47 additions & 25 deletions goto.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,28 @@ def _parse_instructions(code):
extended_arg_offset = None
yield (dis.opname[opcode], oparg, offset)

def _get_instruction_size(opname, oparg=0):
size = 1

extended_arg = oparg >> _BYTECODE.argument_bits
if extended_arg != 0:
size += _get_instruction_size('EXTENDED_ARG', extended_arg)
oparg &= (1 << _BYTECODE.argument_bits) - 1

opcode = dis.opmap[opname]
if opcode >= _BYTECODE.have_argument:
size += _BYTECODE.argument.size

return size

def _get_instructions_size(ops):
size = 0
for op in ops:
if isinstance(op, str):
size += _get_instruction_size(op)
else:
size += _get_instruction_size(*op)
return size

def _write_instruction(buf, pos, opname, oparg=0):
extended_arg = oparg >> _BYTECODE.argument_bits
Expand All @@ -103,6 +125,13 @@ def _write_instruction(buf, pos, opname, oparg=0):

return pos

def _write_instructions(buf, pos, ops):
for op in ops:
if isinstance(op, str):
pos = _write_instruction(buf, pos, op)
else:
pos = _write_instruction(buf, pos, *op)
return pos

def _find_labels_and_gotos(code):
labels = {}
Expand Down Expand Up @@ -165,36 +194,29 @@ def _patch_code(code):
if origin_stack[:target_depth] != target_stack:
raise SyntaxError('Jump into different block')

failed = False
try:
for i in range(len(origin_stack) - target_depth):
pos = _write_instruction(buf, pos, 'POP_BLOCK')

if target >= end:
rel_target = (target - pos) // _BYTECODE.jump_unit
oparg_bits = 0

while True:
rel_target -= (1 + _BYTECODE.argument.size) // _BYTECODE.jump_unit
if rel_target >> oparg_bits == 0:
pos = _write_instruction(buf, pos, 'EXTENDED_ARG', 0)
break
ops = []
for i in range(len(origin_stack) - target_depth):
ops.append('POP_BLOCK')
ops.append(('JUMP_ABSOLUTE', target // _BYTECODE.jump_unit))

oparg_bits += _BYTECODE.argument_bits
if rel_target >> oparg_bits == 0:
break
if pos + _get_instructions_size(ops) > end:
# not enough space, add code at buffer end and jump there
buf_end = len(buf)

pos = _write_instruction(buf, pos, 'JUMP_FORWARD', rel_target)
else:
pos = _write_instruction(buf, pos, 'JUMP_ABSOLUTE', target // _BYTECODE.jump_unit)
go_to_end_ops = [('JUMP_ABSOLUTE', buf_end // _BYTECODE.jump_unit)]

except (IndexError, struct.error):
failed = True
if pos + _get_instructions_size(go_to_end_ops) > end:
# not sure if reachable
raise SyntaxError('Goto in an incredibly huge function')

if failed or pos > end:
raise SyntaxError('Jump out of too many nested blocks')
pos = _write_instructions(buf, pos, go_to_end_ops)
_inject_nop_sled(buf, pos, end)

_inject_nop_sled(buf, pos, end)
buf.extend([0] * _get_instructions_size(ops))
_write_instructions(buf, buf_end, ops)
else:
pos = _write_instructions(buf, pos, ops)
_inject_nop_sled(buf, pos, end)

return _make_code(code, _array_to_bytes(buf))

Expand Down
104 changes: 48 additions & 56 deletions test_goto.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -71,63 +71,55 @@ def func():

pytest.raises(SyntaxError, with_goto, func)

if sys.version_info >= (3, 6):
def test_jump_out_of_nested_2_loops():
@with_goto
def func():
x = 1
for i in range(2):
for j in range(2):
# These are more than 256 bytes of bytecode, requiring
# a JUMP_FORWARD below on Python 3.6+, since the absolute
# address would be too large, after leaving two blocks.
x += x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x
x += x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x
x += x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x

goto .end
label .end
return (i, j)

assert func() == (0, 0)

def test_jump_out_of_nested_3_loops():
def func():
for i in range(2):
for j in range(2):
for k in range(2):
goto .end
label .end
return (i, j, k)

pytest.raises(SyntaxError, with_goto, func)
else:
def test_jump_out_of_nested_4_loops():
@with_goto
def func():
for i in range(2):
for j in range(2):
for k in range(2):
for m in range(2):
goto .end
label .end
return (i, j, k, m)

assert func() == (0, 0, 0, 0)

def test_jump_out_of_nested_5_loops():
def func():
for i in range(2):
for j in range(2):
for k in range(2):
for m in range(2):
for n in range(2):
goto .end
label .end
return (i, j, k, m, n)

pytest.raises(SyntaxError, with_goto, func)
def test_jump_out_of_nested_2_loops():
@with_goto
def func():
x = 1
for i in range(2):
for j in range(2):
# These are more than 256 bytes of bytecode
x += x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x
x += x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x
x += x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x+x

goto .end
label .end
return (i, j)

assert func() == (0, 0)

def test_jump_out_of_nested_11_loops():
@with_goto
def func():
x = 1
for i1 in range(2):
for i2 in range(2):
for i3 in range(2):
for i4 in range(2):
for i5 in range(2):
for i6 in range(2):
for i7 in range(2):
for i8 in range(2):
for i9 in range(2):
for i10 in range(2):
for i11 in range(2):
# These are more than
# 256 bytes of bytecode
x += (x+x+x+x+x+x+x+x+x+
x+x+x+x+x+x+x+x+x+
x+x+x+x+x+x+x+x+x)
x += (x+x+x+x+x+x+x+x+x+
x+x+x+x+x+x+x+x+x+
x+x+x+x+x+x+x+x+x)
x += (x+x+x+x+x+x+x+x+x+
x+x+x+x+x+x+x+x+x+
x+x+x+x+x+x+x+x+x)

goto .end
label .end
return (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11)

assert func() == (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)

def test_jump_across_loops():
def func():
Expand Down