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Fix stack walking bug with respect to pre-converted if statements.

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This commit is contained in:
Jennifer Taylor
2021-05-05 00:56:33 +00:00
parent eba79ed3bc
commit 25278d76c5
1 changed files with 69 additions and 11 deletions
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80
bemani/format/afp/decompile.py
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@@ -955,7 +955,7 @@ class WhileStatement(DoWhileStatement):
class IntermediateIf(ConvertedAction):
def __init__(self, parent_action: IfAction, true_statements: Sequence[Statement], false_statements: Sequence[Statement]) -> None:
def __init__(self, parent_action: Union[IfAction, IfExpr], true_statements: Sequence[Statement], false_statements: Sequence[Statement]) -> None:
self.parent_action = parent_action
self.true_statements = list(true_statements)
self.false_statements = list(false_statements)
@@ -2835,9 +2835,13 @@ class ByteCodeDecompiler(VerboseOutput):
continue
if isinstance(action, IntermediateIf):
# A partially-converted if from loop detection. Let's hoist it out properly.
chunk.actions[i] = IfStatement(
make_if_expr(action.parent_action),
# A partially-converted if from loop detection. Leave as-is, this
# is the job of our caller since it needs to follow the stack to
# the next jump given the statements in this intermediate if. The
# only thing we convert is the expression, since we need the current
# stack to do that.
chunk.actions[i] = IntermediateIf(
make_if_expr(cast(IfAction, action.parent_action)),
action.true_statements,
action.false_statements,
)
@@ -3020,6 +3024,10 @@ class ByteCodeDecompiler(VerboseOutput):
statements.append(DefineLabelStatement(start_id))
# Grab the computed start stack for this ID
if chunk.id not in stacks:
# We somehow failed to assign a stack to this chunk but got here anyway?
raise Exception(f"Logic error, stack for {chunk.id} does not exist!")
stack = stacks[chunk.id]
del stacks[chunk.id]
@@ -3064,7 +3072,7 @@ class ByteCodeDecompiler(VerboseOutput):
self.vprint(f"Evaluating graph of IfBody {if_body_chunk.id} true case")
true_start = self.__get_entry_block(if_body_chunk.true_chunks)
if true_start in stacks:
raise Exception("Logic error, unexpected stack for IF!")
raise Exception("Logic error, unexpected stack for if!")
else:
# The stack for both of these is the leftovers from the previous evaluation as they
# rollover.
@@ -3087,7 +3095,7 @@ class ByteCodeDecompiler(VerboseOutput):
self.vprint(f"Evaluating graph of IfBody {if_body_chunk.id} false case")
false_start = self.__get_entry_block(if_body_chunk.false_chunks)
if false_start in stacks:
raise Exception("Logic error, unexpected stack for IF!")
raise Exception("Logic error, unexpected stack for if!")
else:
# The stack for both of these is the leftovers from the previous evaluation as they
# rollover.
@@ -3116,22 +3124,72 @@ class ByteCodeDecompiler(VerboseOutput):
chunk = if_body_chunk
else:
# We must propagate the stack to the next entry. If it already exists we must merge it.
new_next_id = next_chunk_id
new_next_ids: Set[int] = {next_chunk_id}
if new_statements:
last_new_statement = new_statements[-1]
if isinstance(last_new_statement, GotoStatement):
new_next_id = last_new_statement.location
# Replace the next IDs with just the goto.
new_next_ids = {last_new_statement.location}
if isinstance(last_new_statement, (ThrowStatement, NullReturnStatement, ReturnStatement)):
new_next_id = None
# We don't have a next ID, we're returning.
new_next_ids = set()
if isinstance(last_new_statement, IntermediateIf):
# We have potentially more than one next ID, given what statements exist
# inside the true/false chunks.
intermediates: List[Statement] = []
if len(last_new_statement.true_statements) > 1:
raise Exception(f"Logic error, expected only one true statement in intermediate if {last_new_statement}!")
else:
intermediates.extend(last_new_statement.true_statements)
if len(last_new_statement.false_statements) > 1:
raise Exception(f"Logic error, expected only one false statement in intermediate if {last_new_statement}!")
else:
intermediates.extend(last_new_statement.false_statements)
if new_next_id:
reconcile_stacks(chunk.id, new_next_id, stack_leftovers)
for stmt in intermediates:
if isinstance(stmt, GotoStatement):
new_next_ids.add(stmt.location)
elif isinstance(stmt, (ThrowStatement, NullReturnStatement, ReturnStatement, ContinueStatement)):
# Do nothing. Three of these cases point at the end of the program, one
# points back at the top of the loop which we've already covered. Maybe
# we should assert here like we do below? Not sure.
pass
elif isinstance(stmt, BreakStatement):
# This points at the next chunk ID after the loop.
if next_id is not None:
new_next_ids.add(next_id)
else:
raise Exception(f"Logic error, unexpected statement {stmt}!")
if new_next_ids:
for new_next_id in new_next_ids:
reconcile_stacks(chunk.id, new_next_id, [s for s in stack_leftovers])
# Insert a sentinel for where temporary variables can be added if we
# need to in the future.
sentinels: List[Statement] = [InsertionLocation(chunk.id)]
# If we have a goto, we need to insert the tempvar assignment before it.
if new_statements and isinstance(new_statements[-1], GotoStatement):
sentinels.append(new_statements[-1])
new_statements = new_statements[:-1]
# If we have an intermediate If, we need to insert the tempvar before it
# and also render it out to a real if statement.
if new_statements and isinstance(new_statements[-1], IntermediateIf):
sentinels.append(
IfStatement(
cast(IfExpr, new_statements[-1].parent_action),
new_statements[-1].true_statements,
new_statements[-1].false_statements,
)
)
new_statements = new_statements[:-1]
# Add our new statements to the end of the statement list.
new_statements.extend(sentinels)
else:
# We have nowhere else to go, verify that we have an empty stack.
stack_leftovers = [s for s in stack_leftovers if not isinstance(s, MaybeStackEntry)]
if stack_leftovers:
raise Exception(f"Logic error, reached execution end and have stack entries {stack_leftovers} still!")