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30 lines
963 B
Plaintext
30 lines
963 B
Plaintext
/**
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* @name String concatenation in loop
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* @description Concatenating strings in loops has quadratic performance.
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* @kind problem
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* @tags efficiency
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* maintainability
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* @problem.severity recommendation
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* @sub-severity low
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* @precision low
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* @id py/string-concatenation-in-loop
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*/
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import python
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predicate string_concat_in_loop(BinaryExpr b) {
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b.getOp() instanceof Add
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and
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exists(SsaVariable d, SsaVariable u, BinaryExprNode add, ClassObject str_type |
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add.getNode() = b and d = u.getAnUltimateDefinition() |
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d.getDefinition().(DefinitionNode).getValue() = add and u.getAUse() = add.getAnOperand() and
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add.getAnOperand().refersTo(_, str_type, _) and
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(str_type = theBytesType() or str_type = theUnicodeType())
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)
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}
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from BinaryExpr b, Stmt s
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where string_concat_in_loop(b) and s.getASubExpression() = b
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select s, "String concatenation in a loop is quadratic in the number of iterations."
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