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72 lines
1.9 KiB
Plaintext
72 lines
1.9 KiB
Plaintext
/**
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* @name Variable defined multiple times
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* @description Assignment to a variable occurs multiple times without any intermediate use of that variable
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* @kind problem
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* @tags maintainability
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* useless-code
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* external/cwe/cwe-563
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* @problem.severity warning
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* @sub-severity low
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* @precision very-high
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* @id py/multiple-definition
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*/
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import python
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import Definition
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predicate multiply_defined(AstNode asgn1, AstNode asgn2, Variable v) {
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/*
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* Must be redefined on all possible paths in the CFG corresponding to the original source.
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* For example, splitting may create a path where `def` is unconditionally redefined, even though
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* it is not in the original source.
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*/
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forex(Definition def, Definition redef |
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def.getVariable() = v and
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def = asgn1.getAFlowNode() and
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redef = asgn2.getAFlowNode()
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def.isUnused() and
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def.getARedef() = redef and
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def.isRelevant()
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)
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}
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predicate simple_literal(Expr e) {
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e.(Num).getN() = "0"
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or
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e instanceof NameConstant
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or
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e instanceof List and not exists(e.(List).getAnElt())
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or
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e instanceof Tuple and not exists(e.(Tuple).getAnElt())
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or
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e instanceof Dict and not exists(e.(Dict).getAKey())
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or
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e.(StringLiteral).getText() = ""
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}
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/**
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* Holds if the redefinition is uninteresting.
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*
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* A multiple definition is 'uninteresting' if it sets a variable to a
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* simple literal before reassigning it.
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* x = None
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* if cond:
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* x = value1
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* else:
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* x = value2
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*/
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predicate uninteresting_definition(AstNode asgn1) {
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exists(AssignStmt a | a.getATarget() = asgn1 | simple_literal(a.getValue()))
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}
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from AstNode asgn1, AstNode asgn2, Variable v
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where
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multiply_defined(asgn1, asgn2, v) and
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forall(Name el | el = asgn1.getParentNode().(Tuple).getAnElt() | multiply_defined(el, _, _)) and
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not uninteresting_definition(asgn1)
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select asgn1,
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"This assignment to '" + v.getId() + "' is unnecessary as it is $@ before this value is used.",
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asgn2, "redefined"
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