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JS: Update range analysis to use getImmediatePredecessor

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Asger F
2019-07-31 20:35:56 +01:00
parent 9e949d0f44
commit 8e1893d0ed
2 changed files with 17 additions and 28 deletions
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34
javascript/ql/src/semmle/javascript/RangeAnalysis.qll
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@@ -98,29 +98,6 @@ module RangeAnalysis {
)
}
/**
* Holds if the given node has a unique data flow predecessor.
*/
pragma[noinline]
private predicate hasUniquePredecessor(DataFlow::Node node) {
isRelevant(node) and
strictcount(node.getAPredecessor()) = 1 and
// exclude parameters with default values
not exists(Parameter p |
DataFlow::parameterNode(p) = node and
exists(p.getDefault())
)
}
/**
* Gets the definition of `node`, without unfolding phi nodes.
*/
DataFlow::Node getDefinition(DataFlow::Node node) {
if hasUniquePredecessor(node)
then result = getDefinition(node.getAPredecessor())
else result = node
}
/**
* Gets a data flow node holding the result of the add/subtract operation in
* the given increment/decrement expression.
@@ -229,8 +206,8 @@ module RangeAnalysis {
* Holds if `r` can be modelled as `r = root * sign + bias`.
*/
predicate linearDefinition(DataFlow::Node r, DataFlow::Node root, int sign, Bias bias) {
if hasUniquePredecessor(r)
then linearDefinition(r.getAPredecessor(), root, sign, bias)
if exists(r.getImmediatePredecessor())
then linearDefinition(r.getImmediatePredecessor(), root, sign, bias)
else
if linearDefinitionStep(r, _, _, _)
then
@@ -257,8 +234,8 @@ module RangeAnalysis {
predicate linearDefinitionSum(
DataFlow::Node r, DataFlow::Node xroot, int xsign, DataFlow::Node yroot, int ysign, Bias bias
) {
if hasUniquePredecessor(r)
then linearDefinitionSum(r.getAPredecessor(), xroot, xsign, yroot, ysign, bias)
if exists(r.getImmediatePredecessor())
then linearDefinitionSum(r.getImmediatePredecessor(), xroot, xsign, yroot, ysign, bias)
else
if exists(r.asExpr().getIntValue())
then none() // do not model constants as sums
@@ -336,7 +313,8 @@ module RangeAnalysis {
ConditionGuardNode guard, DataFlow::Node a, int asign, string operator, DataFlow::Node b,
int bsign, Bias bias
) {
exists(Comparison compare | compare = getDefinition(guard.getTest().flow()).asExpr() |
exists(Comparison compare |
compare = guard.getTest().flow().getImmediatePredecessor*().asExpr() and
linearComparison(compare, a, asign, b, bsign, bias) and
(
guard.getOutcome() = true and operator = compare.getOperator()

11
javascript/ql/test/query-tests/Statements/UselessComparisonTest/defaults.js Normal file
View File

@@ -0,0 +1,11 @@
function defaultParam(param = 0) {
if (param > 0) {} // OK
}
function defaultPattern(obj, arr) {
let { prop = 0 } = obj;
if (prop > 0) {} // OK
let [ elm = 0 ] = arr;
if (elm > 0) {} // OK
}