1 | """
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2 | control_flow_pass.py - AST pass that builds a control flow graph.
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3 | """
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4 | import collections
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5 | from typing import overload, Union, Optional, Dict
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6 |
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7 | import mypy
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8 | from mypy.nodes import (Block, Expression, Statement, ExpressionStmt, StrExpr,
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9 | CallExpr, FuncDef, IfStmt, NameExpr, MemberExpr)
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10 |
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11 | from mypy.types import CallableType, Instance, Type, UnionType
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12 |
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13 | from mycpp.crash import catch_errors
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14 | from mycpp.util import join_name, split_py_name
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15 | from mycpp.visitor import SimpleVisitor, T
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16 | from mycpp import util
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17 | from mycpp import pass_state
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18 |
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19 |
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20 | class UnsupportedException(Exception):
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21 | pass
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22 |
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23 |
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24 | class Build(SimpleVisitor):
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25 |
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26 | def __init__(self, types: Dict[Expression, Type], virtual, local_vars,
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27 | dot_exprs):
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28 |
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29 | self.types = types
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30 | self.cfgs = collections.defaultdict(pass_state.ControlFlowGraph)
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31 | self.current_statement_id = None
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32 | self.current_class_name = None
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33 | self.current_func_node = None
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34 | self.loop_stack = []
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35 | self.virtual = virtual
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36 | self.local_vars = local_vars
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37 | self.dot_exprs = dot_exprs
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38 | self.callees = {} # statement object -> SymbolPath of the callee
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39 |
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40 | def current_cfg(self):
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41 | if not self.current_func_node:
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42 | return None
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43 |
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44 | return self.cfgs[split_py_name(self.current_func_node.fullname)]
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45 |
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46 | def resolve_callee(self, o: CallExpr) -> Optional[util.SymbolPath]:
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47 | """
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48 | Returns the fully qualified name of the callee in the given call
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49 | expression.
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50 |
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51 | Member functions are prefixed by the names of the classes that contain
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52 | them. For example, the name of the callee in the last statement of the
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53 | snippet below is `module.SomeObject.Foo`.
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54 |
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55 | x = module.SomeObject()
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56 | x.Foo()
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57 |
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58 | Free-functions defined in the local module are referred to by their
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59 | normal fully qualified names. The function `foo` in a module called
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60 | `moduleA` would is named `moduleA.foo`. Calls to free-functions defined
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61 | in imported modules are named the same way.
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62 | """
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63 |
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64 | if isinstance(o.callee, NameExpr):
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65 | return split_py_name(o.callee.fullname)
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66 |
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67 | elif isinstance(o.callee, MemberExpr):
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68 | if isinstance(o.callee.expr, NameExpr):
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69 | is_module = isinstance(self.dot_exprs.get(o.callee),
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70 | pass_state.ModuleMember)
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71 | if is_module:
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72 | return split_py_name(
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73 | o.callee.expr.fullname) + (o.callee.name, )
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74 |
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75 | elif o.callee.expr.name == 'self':
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76 | assert self.current_class_name
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77 | return self.current_class_name + (o.callee.name, )
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78 |
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79 | else:
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80 | local_type = None
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81 | for name, t in self.local_vars.get(self.current_func_node,
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82 | []):
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83 | if name == o.callee.expr.name:
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84 | local_type = t
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85 | break
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86 |
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87 | if local_type:
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88 | if isinstance(local_type, str):
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89 | return split_py_name(local_type) + (
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90 | o.callee.name, )
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91 |
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92 | elif isinstance(local_type, Instance):
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93 | return split_py_name(
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94 | local_type.type.fullname) + (o.callee.name, )
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95 |
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96 | elif isinstance(local_type, UnionType):
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97 | assert len(local_type.items) == 2
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98 | return split_py_name(
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99 | local_type.items[0].type.fullname) + (
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100 | o.callee.expr.name, )
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101 |
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102 | else:
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103 | assert not isinstance(local_type, CallableType)
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104 | # primitive type or string. don't care.
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105 | return None
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106 |
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107 | else:
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108 | # context or exception handler. probably safe to ignore.
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109 | return None
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110 |
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111 | else:
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112 | t = self.types.get(o.callee.expr)
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113 | if isinstance(t, Instance):
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114 | return split_py_name(t.type.fullname) + (o.callee.name, )
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115 |
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116 | elif isinstance(t, UnionType):
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117 | assert len(t.items) == 2
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118 | return split_py_name(
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119 | t.items[0].type.fullname) + (o.callee.name, )
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120 |
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121 | elif o.callee.expr and getattr(o.callee.expr, 'fullname',
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122 | None):
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123 | return split_py_name(
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124 | o.callee.expr.fullname) + (o.callee.name, )
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125 |
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126 | else:
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127 | # constructors of things that we don't care about.
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128 | return None
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129 |
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130 | # Don't currently get here
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131 | raise AssertionError()
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132 |
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133 | #
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134 | # COPIED from IRBuilder
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135 | #
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136 |
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137 | @overload
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138 | def accept(self, node: Expression) -> T:
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139 | ...
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140 |
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141 | @overload
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142 | def accept(self, node: Statement) -> None:
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143 | ...
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144 |
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145 | def accept(self, node: Union[Statement, Expression]) -> Optional[T]:
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146 | with catch_errors(self.module_path, node.line):
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147 | if isinstance(node, Expression):
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148 | try:
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149 | res = node.accept(self)
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150 | #res = self.coerce(res, self.node_type(node), node.line)
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151 |
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152 | # If we hit an error during compilation, we want to
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153 | # keep trying, so we can produce more error
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154 | # messages. Generate a temp of the right type to keep
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155 | # from causing more downstream trouble.
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156 | except UnsupportedException:
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157 | res = self.alloc_temp(self.node_type(node))
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158 | return res
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159 | else:
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160 | try:
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161 | cfg = self.current_cfg()
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162 | # Most statements have empty visitors because they don't
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163 | # require any special logic. Create statements for them
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164 | # here. Don't create statements from blocks to avoid
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165 | # stuttering.
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166 | if cfg and not isinstance(node, Block):
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167 | self.current_statement_id = cfg.AddStatement()
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168 |
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169 | node.accept(self)
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170 | except UnsupportedException:
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171 | pass
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172 | return None
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173 |
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174 | # Not in superclasses:
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175 |
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176 | def visit_mypy_file(self, o: 'mypy.nodes.MypyFile') -> T:
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177 | if util.ShouldSkipPyFile(o):
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178 | return
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179 |
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180 | self.module_path = o.path
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181 |
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182 | for node in o.defs:
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183 | # skip module docstring
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184 | if isinstance(node, ExpressionStmt) and isinstance(
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185 | node.expr, StrExpr):
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186 | continue
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187 | self.accept(node)
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188 |
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189 | # Statements
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190 |
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191 | def visit_for_stmt(self, o: 'mypy.nodes.ForStmt') -> T:
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192 | cfg = self.current_cfg()
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193 | with pass_state.CfgLoopContext(
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194 | cfg, entry=self.current_statement_id) as loop:
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195 | self.accept(o.expr)
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196 | self.loop_stack.append(loop)
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197 | self.accept(o.body)
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198 | self.loop_stack.pop()
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199 |
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200 | def _handle_switch(self, expr, o, cfg):
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201 | assert len(o.body.body) == 1, o.body.body
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202 | if_node = o.body.body[0]
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203 | assert isinstance(if_node, IfStmt), if_node
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204 | cases = []
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205 | default_block = util._collect_cases(self.module_path, if_node, cases)
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206 | with pass_state.CfgBranchContext(
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207 | cfg, self.current_statement_id) as branch_ctx:
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208 | for expr, body in cases:
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209 | self.accept(expr)
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210 | assert expr is not None, expr
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211 | with branch_ctx.AddBranch():
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212 | self.accept(body)
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213 |
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214 | if default_block:
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215 | with branch_ctx.AddBranch():
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216 | self.accept(default_block)
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217 |
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218 | def visit_with_stmt(self, o: 'mypy.nodes.WithStmt') -> T:
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219 | cfg = self.current_cfg()
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220 | assert len(o.expr) == 1, o.expr
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221 | expr = o.expr[0]
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222 | assert isinstance(expr, CallExpr), expr
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223 | self.accept(expr)
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224 |
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225 | callee_name = expr.callee.name
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226 | if callee_name == 'switch':
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227 | self._handle_switch(expr, o, cfg)
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228 | elif callee_name == 'str_switch':
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229 | self._handle_switch(expr, o, cfg)
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230 | elif callee_name == 'tagswitch':
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231 | self._handle_switch(expr, o, cfg)
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232 | else:
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233 | with pass_state.CfgBlockContext(cfg, self.current_statement_id):
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234 | self.accept(o.body)
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235 |
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236 | def visit_func_def(self, o: 'mypy.nodes.FuncDef') -> T:
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237 | if o.name == '__repr__': # Don't translate
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238 | return
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239 |
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240 | # For virtual methods, pretend that the method on the base class calls
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241 | # the same method on every subclass. This way call sites using the
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242 | # abstract base class will over-approximate the set of call paths they
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243 | # can take when checking if they can reach MaybeCollect().
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244 | if self.current_class_name and self.virtual.IsVirtual(
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245 | self.current_class_name, o.name):
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246 | key = (self.current_class_name, o.name)
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247 | base = self.virtual.virtuals[key]
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248 | if base:
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249 | sub = join_name(self.current_class_name + (o.name, ),
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250 | delim='.')
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251 | base_key = base[0] + (base[1], )
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252 | cfg = self.cfgs[base_key]
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253 | cfg.AddFact(0, pass_state.FunctionCall(sub))
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254 |
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255 | self.current_func_node = o
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256 | self.accept(o.body)
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257 | self.current_func_node = None
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258 | self.current_statement_id = None
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259 |
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260 | def visit_class_def(self, o: 'mypy.nodes.ClassDef') -> T:
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261 | self.current_class_name = split_py_name(o.fullname)
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262 | for stmt in o.defs.body:
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263 | # Ignore things that look like docstrings
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264 | if (isinstance(stmt, ExpressionStmt) and
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265 | isinstance(stmt.expr, StrExpr)):
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266 | continue
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267 |
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268 | if isinstance(stmt, FuncDef) and stmt.name == '__repr__':
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269 | continue
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270 |
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271 | self.accept(stmt)
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272 |
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273 | self.current_class_name = None
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274 |
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275 | def visit_while_stmt(self, o: 'mypy.nodes.WhileStmt') -> T:
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276 | cfg = self.current_cfg()
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277 | with pass_state.CfgLoopContext(
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278 | cfg, entry=self.current_statement_id) as loop:
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279 | self.accept(o.expr)
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280 | self.loop_stack.append(loop)
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281 | self.accept(o.body)
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282 | self.loop_stack.pop()
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283 |
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284 | def visit_return_stmt(self, o: 'mypy.nodes.ReturnStmt') -> T:
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285 | cfg = self.current_cfg()
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286 | if cfg:
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287 | cfg.AddDeadend(self.current_statement_id)
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288 |
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289 | if o.expr:
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290 | self.accept(o.expr)
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291 |
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292 | def visit_if_stmt(self, o: 'mypy.nodes.IfStmt') -> T:
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293 | cfg = self.current_cfg()
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294 | for expr in o.expr:
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295 | self.accept(expr)
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296 |
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297 | with pass_state.CfgBranchContext(
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298 | cfg, self.current_statement_id) as branch_ctx:
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299 | with branch_ctx.AddBranch():
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300 | for node in o.body:
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301 | self.accept(node)
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302 |
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303 | if o.else_body:
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304 | with branch_ctx.AddBranch():
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305 | self.accept(o.else_body)
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306 |
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307 | def visit_break_stmt(self, o: 'mypy.nodes.BreakStmt') -> T:
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308 | if len(self.loop_stack):
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309 | self.loop_stack[-1].AddBreak(self.current_statement_id)
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310 |
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311 | def visit_continue_stmt(self, o: 'mypy.nodes.ContinueStmt') -> T:
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312 | if len(self.loop_stack):
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313 | self.loop_stack[-1].AddContinue(self.current_statement_id)
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314 |
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315 | def visit_raise_stmt(self, o: 'mypy.nodes.RaiseStmt') -> T:
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316 | cfg = self.current_cfg()
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317 | if cfg:
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318 | cfg.AddDeadend(self.current_statement_id)
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319 |
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320 | if o.expr:
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321 | self.accept(o.expr)
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322 |
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323 | def visit_try_stmt(self, o: 'mypy.nodes.TryStmt') -> T:
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324 | cfg = self.current_cfg()
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325 | with pass_state.CfgBranchContext(cfg,
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326 | self.current_statement_id) as try_ctx:
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327 | with try_ctx.AddBranch() as try_block:
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328 | self.accept(o.body)
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329 |
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330 | for t, v, handler in zip(o.types, o.vars, o.handlers):
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331 | with try_ctx.AddBranch(try_block.exit):
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332 | self.accept(handler)
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333 |
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334 | # Expressions
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335 |
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336 | def visit_call_expr(self, o: 'mypy.nodes.CallExpr') -> T:
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337 | cfg = self.current_cfg()
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338 | if self.current_func_node:
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339 | full_callee = self.resolve_callee(o)
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340 | if full_callee:
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341 | self.callees[o] = full_callee
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342 | cfg.AddFact(
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343 | self.current_statement_id,
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344 | pass_state.FunctionCall(join_name(full_callee, delim='.')))
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345 |
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346 | self.accept(o.callee)
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347 | for arg in o.args:
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348 | self.accept(arg)
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