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Java: Fix regression.

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This commit is contained in:
Anders Schack-Mulligen
2018-10-16 11:29:15 +02:00
parent 1a66f7e249
commit 26009065af
2 changed files with 34 additions and 3 deletions
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26
java/ql/src/semmle/code/java/dataflow/RangeAnalysis.qll
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@@ -133,21 +133,41 @@ private predicate boundCondition(ComparisonExpr comp, SsaVariable v, Expr e, int
)
}
private predicate gcdInput(int x, int y) {
exists(ComparisonExpr comp, Bound b |
exprModulus(comp.getLesserOperand(), b, _, x) and
exprModulus(comp.getGreaterOperand(), b, _, y)
) or
exists(int x0, int y0 |
gcdInput(x0, y0) and
x = y0 and
y = x0 % y0
)
}
private int gcd(int x, int y) {
result = x.abs() and y = 0 and gcdInput(x, y)
or
result = gcd(y, x % y) and y != 0 and gcdInput(x, y)
}
/**
* Holds if `comp` is a comparison between `x` and `y` for which `y - x` has a
* fixed value modulo some `mod > 1`, such that the comparison can be
* strengthened by `strengthen` when evaluating to `testIsTrue`.
*/
private predicate modulusComparison(ComparisonExpr comp, boolean testIsTrue, int strengthen) {
exists(Bound b, int v1, int v2, int mod, boolean resultIsStrict, int d, int k |
exists(Bound b, int v1, int v2, int mod1, int mod2, int mod, boolean resultIsStrict, int d, int k |
// If `x <= y` and `x =(mod) b + v1` and `y =(mod) b + v2` then
// `0 <= y - x =(mod) v2 - v1`. By choosing `k =(mod) v2 - v1` with
// `0 <= k < mod` we get `k <= y - x`. If the resulting comparison is
// strict then the strengthening amount is instead `k - 1` modulo `mod`:
// `x < y` means `0 <= y - x - 1 =(mod) k - 1` so `k - 1 <= y - x - 1` and
// thus `k - 1 < y - x` with `0 <= k - 1 < mod`.
exprModulus(comp.getLesserOperand(), b, v1, mod) and
exprModulus(comp.getGreaterOperand(), b, v2, mod) and
exprModulus(comp.getLesserOperand(), b, v1, mod1) and
exprModulus(comp.getGreaterOperand(), b, v2, mod2) and
mod = gcd(mod1, mod2) and
mod != 1 and
(testIsTrue = true or testIsTrue = false) and
(if comp.isStrict() then resultIsStrict = testIsTrue else resultIsStrict = testIsTrue.booleanNot()) and
(resultIsStrict = true and d = 1 or resultIsStrict = false and d = 0) and