| 1 | """
|
| 2 | control_flow_pass.py - AST pass that builds a control flow graph.
|
| 3 | """
|
| 4 | import collections
|
| 5 | from typing import overload, Union, Optional, Dict
|
| 6 |
|
| 7 | import mypy
|
| 8 | from mypy.nodes import (Block, Expression, Statement, ExpressionStmt, StrExpr,
|
| 9 | CallExpr, FuncDef, IfStmt, NameExpr, MemberExpr,
|
| 10 | IndexExpr, TupleExpr, IntExpr)
|
| 11 |
|
| 12 | from mypy.types import CallableType, Instance, Type, UnionType, NoneTyp, TupleType
|
| 13 |
|
| 14 | from mycpp.crash import catch_errors
|
| 15 | from mycpp.util import join_name, split_py_name
|
| 16 | from mycpp.visitor import SimpleVisitor, T
|
| 17 | from mycpp import util
|
| 18 | from mycpp import pass_state
|
| 19 |
|
| 20 |
|
| 21 | class UnsupportedException(Exception):
|
| 22 | pass
|
| 23 |
|
| 24 |
|
| 25 | def GetObjectTypeName(t: Type) -> util.SymbolPath:
|
| 26 | if isinstance(t, Instance):
|
| 27 | return split_py_name(t.type.fullname)
|
| 28 |
|
| 29 | elif isinstance(t, UnionType):
|
| 30 | assert len(t.items) == 2
|
| 31 | if isinstance(t.items[0], NoneTyp):
|
| 32 | return GetObjectTypeName(t.items[1])
|
| 33 |
|
| 34 | return GetObjectTypeName(t.items[0])
|
| 35 |
|
| 36 | assert False, t
|
| 37 |
|
| 38 |
|
| 39 | class Build(SimpleVisitor):
|
| 40 |
|
| 41 | def __init__(self, types: Dict[Expression, Type], virtual, local_vars,
|
| 42 | dot_exprs):
|
| 43 |
|
| 44 | self.types = types
|
| 45 | self.cfgs = collections.defaultdict(pass_state.ControlFlowGraph)
|
| 46 | self.current_statement_id = None
|
| 47 | self.current_class_name = None
|
| 48 | self.current_func_node = None
|
| 49 | self.loop_stack = []
|
| 50 | self.virtual = virtual
|
| 51 | self.local_vars = local_vars
|
| 52 | self.dot_exprs = dot_exprs
|
| 53 | self.callees = {} # statement object -> SymbolPath of the callee
|
| 54 |
|
| 55 | def current_cfg(self):
|
| 56 | if not self.current_func_node:
|
| 57 | return None
|
| 58 |
|
| 59 | return self.cfgs[split_py_name(self.current_func_node.fullname)]
|
| 60 |
|
| 61 | def resolve_callee(self, o: CallExpr) -> Optional[util.SymbolPath]:
|
| 62 | """
|
| 63 | Returns the fully qualified name of the callee in the given call
|
| 64 | expression.
|
| 65 |
|
| 66 | Member functions are prefixed by the names of the classes that contain
|
| 67 | them. For example, the name of the callee in the last statement of the
|
| 68 | snippet below is `module.SomeObject.Foo`.
|
| 69 |
|
| 70 | x = module.SomeObject()
|
| 71 | x.Foo()
|
| 72 |
|
| 73 | Free-functions defined in the local module are referred to by their
|
| 74 | normal fully qualified names. The function `foo` in a module called
|
| 75 | `moduleA` would is named `moduleA.foo`. Calls to free-functions defined
|
| 76 | in imported modules are named the same way.
|
| 77 | """
|
| 78 |
|
| 79 | if isinstance(o.callee, NameExpr):
|
| 80 | return split_py_name(o.callee.fullname)
|
| 81 |
|
| 82 | elif isinstance(o.callee, MemberExpr):
|
| 83 | if isinstance(o.callee.expr, NameExpr):
|
| 84 | is_module = isinstance(self.dot_exprs.get(o.callee),
|
| 85 | pass_state.ModuleMember)
|
| 86 | if is_module:
|
| 87 | return split_py_name(
|
| 88 | o.callee.expr.fullname) + (o.callee.name, )
|
| 89 |
|
| 90 | elif o.callee.expr.name == 'self':
|
| 91 | assert self.current_class_name
|
| 92 | return self.current_class_name + (o.callee.name, )
|
| 93 |
|
| 94 | else:
|
| 95 | local_type = None
|
| 96 | for name, t in self.local_vars.get(self.current_func_node,
|
| 97 | []):
|
| 98 | if name == o.callee.expr.name:
|
| 99 | local_type = t
|
| 100 | break
|
| 101 |
|
| 102 | if local_type:
|
| 103 | if isinstance(local_type, str):
|
| 104 | return split_py_name(local_type) + (
|
| 105 | o.callee.name, )
|
| 106 |
|
| 107 | elif isinstance(local_type, Instance):
|
| 108 | return split_py_name(
|
| 109 | local_type.type.fullname) + (o.callee.name, )
|
| 110 |
|
| 111 | elif isinstance(local_type, UnionType):
|
| 112 | assert len(local_type.items) == 2
|
| 113 | return split_py_name(
|
| 114 | local_type.items[0].type.fullname) + (
|
| 115 | o.callee.expr.name, )
|
| 116 |
|
| 117 | else:
|
| 118 | assert not isinstance(local_type, CallableType)
|
| 119 | # primitive type or string. don't care.
|
| 120 | return None
|
| 121 |
|
| 122 | else:
|
| 123 | # context or exception handler. probably safe to ignore.
|
| 124 | return None
|
| 125 |
|
| 126 | else:
|
| 127 | t = self.types.get(o.callee.expr)
|
| 128 | if isinstance(t, Instance):
|
| 129 | return split_py_name(t.type.fullname) + (o.callee.name, )
|
| 130 |
|
| 131 | elif isinstance(t, UnionType):
|
| 132 | assert len(t.items) == 2
|
| 133 | return split_py_name(
|
| 134 | t.items[0].type.fullname) + (o.callee.name, )
|
| 135 |
|
| 136 | elif o.callee.expr and getattr(o.callee.expr, 'fullname',
|
| 137 | None):
|
| 138 | return split_py_name(
|
| 139 | o.callee.expr.fullname) + (o.callee.name, )
|
| 140 |
|
| 141 | else:
|
| 142 | # constructors of things that we don't care about.
|
| 143 | return None
|
| 144 |
|
| 145 | # Don't currently get here
|
| 146 | raise AssertionError()
|
| 147 |
|
| 148 | def get_variable_name(self, expr: Expression) -> Optional[util.SymbolPath]:
|
| 149 | """
|
| 150 | To do dataflow analysis we need to track changes to objects, which
|
| 151 | requires naming them. This function returns the name of the object
|
| 152 | referred to by the given expression. If the expression doesn't refer to
|
| 153 | an object or variable it returns None.
|
| 154 |
|
| 155 | Objects are named slightly differently than they appear in the source
|
| 156 | code.
|
| 157 |
|
| 158 | Objects referenced by local variables are referred to by the name of the
|
| 159 | local. For example, the name of the object in both statements below is
|
| 160 | `x`.
|
| 161 |
|
| 162 | x = module.SomeObject()
|
| 163 | x = None
|
| 164 |
|
| 165 | Member expressions are named after the parent object's type. For
|
| 166 | example, the names of the objects in the member assignment statements
|
| 167 | below are both `module.SomeObject.member_a`. This makes it possible to
|
| 168 | track data flow across object members without having to track individual
|
| 169 | heap objects, which would increase the search space for analyses and
|
| 170 | slow things down.
|
| 171 |
|
| 172 | x = module.SomeObject()
|
| 173 | y = module.SomeObject()
|
| 174 | x.member_a = 'foo'
|
| 175 | y.member_a = 'bar'
|
| 176 |
|
| 177 | Index expressions are named after their bases, for the same reasons as
|
| 178 | member expressions. The coarse-grained precision should lead to an
|
| 179 | over-approximation of where objects are in use, but should not miss any
|
| 180 | references. This should be fine for our purposes. In the snippet below
|
| 181 | the last two assignments are named `x` and `module.SomeObject.a_list`.
|
| 182 |
|
| 183 | x = [None] # list[Thing]
|
| 184 | y = module.SomeObject()
|
| 185 | x[0] = Thing()
|
| 186 | y.a_list[1] = Blah()
|
| 187 |
|
| 188 | Index expressions over tuples are treated differently, though. Tuples
|
| 189 | have a fixed size, tend to be small, and their elements have distinct
|
| 190 | types. So, each element can be (and probably needs to be) individually
|
| 191 | named. In the snippet below, the name of the RHS in the second
|
| 192 | assignment is `t.0`.
|
| 193 |
|
| 194 | t = (1, 2, 3, 4)
|
| 195 | x = t[0]
|
| 196 |
|
| 197 | The examples above all deal with assignments, but these rules apply to
|
| 198 | any expression that uses an object or variable.
|
| 199 | """
|
| 200 | if isinstance(expr,
|
| 201 | NameExpr) and expr.name not in {'True', 'False', 'None'}:
|
| 202 | return (expr.name, )
|
| 203 |
|
| 204 | elif isinstance(expr, MemberExpr):
|
| 205 | dot_expr = self.dot_exprs[expr]
|
| 206 | if isinstance(dot_expr, pass_state.ModuleMember):
|
| 207 | return dot_expr.module_path + (dot_expr.member, )
|
| 208 |
|
| 209 | elif isinstance(dot_expr, pass_state.HeapObjectMember):
|
| 210 | return GetObjectTypeName(
|
| 211 | dot_expr.object_type) + (dot_expr.member, )
|
| 212 |
|
| 213 | elif isinstance(dot_expr, pass_state.StackObjectMember):
|
| 214 | return GetObjectTypeName(
|
| 215 | dot_expr.object_type) + (dot_expr.member, )
|
| 216 |
|
| 217 | elif isinstance(expr, IndexExpr):
|
| 218 | if isinstance(self.types[expr.base], TupleType):
|
| 219 | assert isinstance(expr.index, IntExpr)
|
| 220 | return self.get_variable_name(expr.base) + (str(expr.index.value),)
|
| 221 |
|
| 222 | return self.get_variable_name(expr.base)
|
| 223 |
|
| 224 | return None
|
| 225 |
|
| 226 | #
|
| 227 | # COPIED from IRBuilder
|
| 228 | #
|
| 229 |
|
| 230 | @overload
|
| 231 | def accept(self, node: Expression) -> T:
|
| 232 | ...
|
| 233 |
|
| 234 | @overload
|
| 235 | def accept(self, node: Statement) -> None:
|
| 236 | ...
|
| 237 |
|
| 238 | def accept(self, node: Union[Statement, Expression]) -> Optional[T]:
|
| 239 | with catch_errors(self.module_path, node.line):
|
| 240 | if isinstance(node, Expression):
|
| 241 | try:
|
| 242 | res = node.accept(self)
|
| 243 | #res = self.coerce(res, self.node_type(node), node.line)
|
| 244 |
|
| 245 | # If we hit an error during compilation, we want to
|
| 246 | # keep trying, so we can produce more error
|
| 247 | # messages. Generate a temp of the right type to keep
|
| 248 | # from causing more downstream trouble.
|
| 249 | except UnsupportedException:
|
| 250 | res = self.alloc_temp(self.node_type(node))
|
| 251 | return res
|
| 252 | else:
|
| 253 | try:
|
| 254 | cfg = self.current_cfg()
|
| 255 | # Most statements have empty visitors because they don't
|
| 256 | # require any special logic. Create statements for them
|
| 257 | # here. Don't create statements from blocks to avoid
|
| 258 | # stuttering.
|
| 259 | if cfg and not isinstance(node, Block):
|
| 260 | self.current_statement_id = cfg.AddStatement()
|
| 261 |
|
| 262 | node.accept(self)
|
| 263 | except UnsupportedException:
|
| 264 | pass
|
| 265 | return None
|
| 266 |
|
| 267 | # Not in superclasses:
|
| 268 |
|
| 269 | def visit_mypy_file(self, o: 'mypy.nodes.MypyFile') -> T:
|
| 270 | if util.ShouldSkipPyFile(o):
|
| 271 | return
|
| 272 |
|
| 273 | self.module_path = o.path
|
| 274 |
|
| 275 | for node in o.defs:
|
| 276 | # skip module docstring
|
| 277 | if isinstance(node, ExpressionStmt) and isinstance(
|
| 278 | node.expr, StrExpr):
|
| 279 | continue
|
| 280 | self.accept(node)
|
| 281 |
|
| 282 | # Statements
|
| 283 |
|
| 284 | def visit_for_stmt(self, o: 'mypy.nodes.ForStmt') -> T:
|
| 285 | cfg = self.current_cfg()
|
| 286 | with pass_state.CfgLoopContext(
|
| 287 | cfg, entry=self.current_statement_id) as loop:
|
| 288 | self.accept(o.expr)
|
| 289 | self.loop_stack.append(loop)
|
| 290 | self.accept(o.body)
|
| 291 | self.loop_stack.pop()
|
| 292 |
|
| 293 | def _handle_switch(self, expr, o, cfg):
|
| 294 | assert len(o.body.body) == 1, o.body.body
|
| 295 | if_node = o.body.body[0]
|
| 296 | assert isinstance(if_node, IfStmt), if_node
|
| 297 | cases = []
|
| 298 | default_block = util._collect_cases(self.module_path, if_node, cases)
|
| 299 | with pass_state.CfgBranchContext(
|
| 300 | cfg, self.current_statement_id) as branch_ctx:
|
| 301 | for expr, body in cases:
|
| 302 | self.accept(expr)
|
| 303 | assert expr is not None, expr
|
| 304 | with branch_ctx.AddBranch():
|
| 305 | self.accept(body)
|
| 306 |
|
| 307 | if default_block:
|
| 308 | with branch_ctx.AddBranch():
|
| 309 | self.accept(default_block)
|
| 310 |
|
| 311 | def visit_with_stmt(self, o: 'mypy.nodes.WithStmt') -> T:
|
| 312 | cfg = self.current_cfg()
|
| 313 | assert len(o.expr) == 1, o.expr
|
| 314 | expr = o.expr[0]
|
| 315 | assert isinstance(expr, CallExpr), expr
|
| 316 | self.accept(expr)
|
| 317 |
|
| 318 | callee_name = expr.callee.name
|
| 319 | if callee_name == 'switch':
|
| 320 | self._handle_switch(expr, o, cfg)
|
| 321 | elif callee_name == 'str_switch':
|
| 322 | self._handle_switch(expr, o, cfg)
|
| 323 | elif callee_name == 'tagswitch':
|
| 324 | self._handle_switch(expr, o, cfg)
|
| 325 | else:
|
| 326 | with pass_state.CfgBlockContext(cfg, self.current_statement_id):
|
| 327 | self.accept(o.body)
|
| 328 |
|
| 329 | def visit_func_def(self, o: 'mypy.nodes.FuncDef') -> T:
|
| 330 | if o.name == '__repr__': # Don't translate
|
| 331 | return
|
| 332 |
|
| 333 | # For virtual methods, pretend that the method on the base class calls
|
| 334 | # the same method on every subclass. This way call sites using the
|
| 335 | # abstract base class will over-approximate the set of call paths they
|
| 336 | # can take when checking if they can reach MaybeCollect().
|
| 337 | if self.current_class_name and self.virtual.IsVirtual(
|
| 338 | self.current_class_name, o.name):
|
| 339 | key = (self.current_class_name, o.name)
|
| 340 | base = self.virtual.virtuals[key]
|
| 341 | if base:
|
| 342 | sub = join_name(self.current_class_name + (o.name, ),
|
| 343 | delim='.')
|
| 344 | base_key = base[0] + (base[1], )
|
| 345 | cfg = self.cfgs[base_key]
|
| 346 | cfg.AddFact(0, pass_state.FunctionCall(sub))
|
| 347 |
|
| 348 | self.current_func_node = o
|
| 349 | cfg = self.current_cfg()
|
| 350 | for arg in o.arguments:
|
| 351 | cfg.AddFact(0, pass_state.Definition((arg.variable.name,)))
|
| 352 |
|
| 353 | self.accept(o.body)
|
| 354 | self.current_func_node = None
|
| 355 | self.current_statement_id = None
|
| 356 |
|
| 357 | def visit_class_def(self, o: 'mypy.nodes.ClassDef') -> T:
|
| 358 | self.current_class_name = split_py_name(o.fullname)
|
| 359 | for stmt in o.defs.body:
|
| 360 | # Ignore things that look like docstrings
|
| 361 | if (isinstance(stmt, ExpressionStmt) and
|
| 362 | isinstance(stmt.expr, StrExpr)):
|
| 363 | continue
|
| 364 |
|
| 365 | if isinstance(stmt, FuncDef) and stmt.name == '__repr__':
|
| 366 | continue
|
| 367 |
|
| 368 | self.accept(stmt)
|
| 369 |
|
| 370 | self.current_class_name = None
|
| 371 |
|
| 372 | def visit_while_stmt(self, o: 'mypy.nodes.WhileStmt') -> T:
|
| 373 | cfg = self.current_cfg()
|
| 374 | with pass_state.CfgLoopContext(
|
| 375 | cfg, entry=self.current_statement_id) as loop:
|
| 376 | self.accept(o.expr)
|
| 377 | self.loop_stack.append(loop)
|
| 378 | self.accept(o.body)
|
| 379 | self.loop_stack.pop()
|
| 380 |
|
| 381 | def visit_return_stmt(self, o: 'mypy.nodes.ReturnStmt') -> T:
|
| 382 | cfg = self.current_cfg()
|
| 383 | if cfg:
|
| 384 | cfg.AddDeadend(self.current_statement_id)
|
| 385 |
|
| 386 | if o.expr:
|
| 387 | self.accept(o.expr)
|
| 388 |
|
| 389 | def visit_if_stmt(self, o: 'mypy.nodes.IfStmt') -> T:
|
| 390 | cfg = self.current_cfg()
|
| 391 |
|
| 392 | if util.ShouldVisitIfExpr(o):
|
| 393 | for expr in o.expr:
|
| 394 | self.accept(expr)
|
| 395 |
|
| 396 | with pass_state.CfgBranchContext(
|
| 397 | cfg, self.current_statement_id) as branch_ctx:
|
| 398 | if util.ShouldVisitIfBody(o):
|
| 399 | with branch_ctx.AddBranch():
|
| 400 | for node in o.body:
|
| 401 | self.accept(node)
|
| 402 |
|
| 403 | if util.ShouldVisitElseBody(o):
|
| 404 | with branch_ctx.AddBranch():
|
| 405 | self.accept(o.else_body)
|
| 406 |
|
| 407 | def visit_break_stmt(self, o: 'mypy.nodes.BreakStmt') -> T:
|
| 408 | if len(self.loop_stack):
|
| 409 | self.loop_stack[-1].AddBreak(self.current_statement_id)
|
| 410 |
|
| 411 | def visit_continue_stmt(self, o: 'mypy.nodes.ContinueStmt') -> T:
|
| 412 | if len(self.loop_stack):
|
| 413 | self.loop_stack[-1].AddContinue(self.current_statement_id)
|
| 414 |
|
| 415 | def visit_raise_stmt(self, o: 'mypy.nodes.RaiseStmt') -> T:
|
| 416 | cfg = self.current_cfg()
|
| 417 | if cfg:
|
| 418 | cfg.AddDeadend(self.current_statement_id)
|
| 419 |
|
| 420 | if o.expr:
|
| 421 | self.accept(o.expr)
|
| 422 |
|
| 423 | def visit_try_stmt(self, o: 'mypy.nodes.TryStmt') -> T:
|
| 424 | cfg = self.current_cfg()
|
| 425 | with pass_state.CfgBranchContext(cfg,
|
| 426 | self.current_statement_id) as try_ctx:
|
| 427 | with try_ctx.AddBranch() as try_block:
|
| 428 | self.accept(o.body)
|
| 429 |
|
| 430 | for t, v, handler in zip(o.types, o.vars, o.handlers):
|
| 431 | with try_ctx.AddBranch(try_block.exit):
|
| 432 | self.accept(handler)
|
| 433 |
|
| 434 | def visit_assignment_stmt(self, o: 'mypy.nodes.AssignmentStmt') -> T:
|
| 435 | cfg = self.current_cfg()
|
| 436 | if cfg:
|
| 437 | assert len(o.lvalues) == 1
|
| 438 | lval = o.lvalues[0]
|
| 439 | lval_names = []
|
| 440 | if isinstance(lval, TupleExpr):
|
| 441 | lval_names.extend(
|
| 442 | [self.get_variable_name(item) for item in lval.items])
|
| 443 |
|
| 444 | else:
|
| 445 | lval_names.append(self.get_variable_name(lval))
|
| 446 |
|
| 447 | assert lval_names, o
|
| 448 |
|
| 449 | rval_type = self.types[o.rvalue]
|
| 450 | rval_names = []
|
| 451 | if isinstance(o.rvalue, CallExpr):
|
| 452 | # The RHS is either an object constructor or something that
|
| 453 | # returns a primitive type (e.g. Tuple[int, int] or str).
|
| 454 | # XXX: When we add inter-procedural analysis we should treat
|
| 455 | # these not as definitions but as some new kind of assignment.
|
| 456 | rval_names = [None for _ in lval_names]
|
| 457 |
|
| 458 | elif isinstance(o.rvalue, TupleExpr) and len(lval_names) == 1:
|
| 459 | # We're constructing a tuple. Since tuples have have a fixed
|
| 460 | # (and usually small) size, we can name each of the
|
| 461 | # elements.
|
| 462 | base = lval_names[0]
|
| 463 | lval_names = [
|
| 464 | base + (str(i), ) for i in range(len(o.rvalue.items))
|
| 465 | ]
|
| 466 | rval_names = [
|
| 467 | self.get_variable_name(item) for item in o.rvalue.items
|
| 468 | ]
|
| 469 |
|
| 470 | elif isinstance(rval_type, TupleType):
|
| 471 | # We're unpacking a tuple. Like the tuple construction case,
|
| 472 | # give each element a name.
|
| 473 | rval_name = self.get_variable_name(o.rvalue)
|
| 474 | assert rval_name, o.rvalue
|
| 475 | rval_names = [
|
| 476 | rval_name + (str(i), ) for i in range(len(lval_names))
|
| 477 | ]
|
| 478 |
|
| 479 | else:
|
| 480 | rval_names = [self.get_variable_name(o.rvalue)]
|
| 481 |
|
| 482 | assert len(rval_names) == len(lval_names)
|
| 483 |
|
| 484 | for lhs, rhs in zip(lval_names, rval_names):
|
| 485 | assert lhs, lval
|
| 486 | if rhs:
|
| 487 | # In this case rhe RHS is another variable. Record the
|
| 488 | # assignment so we can keep track of aliases.
|
| 489 | cfg.AddFact(self.current_statement_id,
|
| 490 | pass_state.Assignment(lhs, rhs))
|
| 491 | else:
|
| 492 | # In this case the RHS is either some kind of literal (e.g.
|
| 493 | # [] or 'foo') or a call to an object constructor. Mark this
|
| 494 | # statement as an (re-)definition of a variable.
|
| 495 | cfg.AddFact(
|
| 496 | self.current_statement_id,
|
| 497 | pass_state.Definition(lhs),
|
| 498 | )
|
| 499 |
|
| 500 | for lval in o.lvalues:
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| 501 | self.accept(lval)
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| 502 |
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| 503 | self.accept(o.rvalue)
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| 504 |
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| 505 | # Expressions
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| 506 |
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| 507 | def visit_call_expr(self, o: 'mypy.nodes.CallExpr') -> T:
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| 508 | cfg = self.current_cfg()
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| 509 | if self.current_func_node:
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| 510 | full_callee = self.resolve_callee(o)
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| 511 | if full_callee:
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| 512 | self.callees[o] = full_callee
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| 513 | cfg.AddFact(
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| 514 | self.current_statement_id,
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| 515 | pass_state.FunctionCall(join_name(full_callee, delim='.')))
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| 516 |
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| 517 | self.accept(o.callee)
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| 518 | for arg in o.args:
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| 519 | self.accept(arg)
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