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Check array length > 0 on array access even if index is unknown

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Fixes IDEA-246390 DFA skips the warning "Array index is out of bounds" in for-loop

GitOrigin-RevId: 828e7353ad7220472818b10f4d4c51c5a8eeba64
This commit is contained in:
Tagir Valeev
2020-07-23 10:46:24 +07:00
committed by intellij-monorepo-bot
parent 477e161c7d
commit ecb8fba035
2 changed files with 20 additions and 13 deletions
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28
java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/StandardInstructionVisitor.java
View File

@@ -164,19 +164,7 @@ public class StandardInstructionVisitor extends InstructionVisitor {
PsiArrayAccessExpression arrayExpression = instruction.getExpression();
DfaValue index = memState.pop();
DfaValue array = memState.pop();
boolean alwaysOutOfBounds = false;
DfaValueFactory factory = runner.getFactory();
if (!DfaTypeValue.isUnknown(index)) {
DfaCondition indexNonNegative = index.cond(RelationType.GE, factory.getInt(0));
if (!memState.applyCondition(indexNonNegative)) {
alwaysOutOfBounds = true;
}
DfaValue dfaLength = SpecialField.ARRAY_LENGTH.createValue(factory, array);
DfaCondition indexLessThanLength = index.cond(RelationType.LT, dfaLength);
if (!memState.applyCondition(indexLessThanLength)) {
alwaysOutOfBounds = true;
}
}
boolean alwaysOutOfBounds = !applyBoundsCheck(memState, array, index);
processArrayAccess(arrayExpression, alwaysOutOfBounds);
if (alwaysOutOfBounds) {
DfaControlTransferValue transfer = instruction.getOutOfBoundsExceptionTransfer();
@@ -207,6 +195,20 @@ public class StandardInstructionVisitor extends InstructionVisitor {
return nextInstruction(instruction, runner, memState);
}
private static boolean applyBoundsCheck(@NotNull DfaMemoryState memState,
@NotNull DfaValue array,
@NotNull DfaValue index) {
DfaValueFactory factory = index.getFactory();
DfaValue length = SpecialField.ARRAY_LENGTH.createValue(factory, array);
DfaCondition lengthMoreThanZero = length.cond(RelationType.GT, factory.getInt(0));
if (!memState.applyCondition(lengthMoreThanZero)) return false;
DfaCondition indexNonNegative = index.cond(RelationType.GE, factory.getInt(0));
if (!memState.applyCondition(indexNonNegative)) return false;
DfaCondition indexLessThanLength = index.cond(RelationType.LT, length);
if (!memState.applyCondition(indexLessThanLength)) return false;
return true;
}
protected void processArrayAccess(PsiArrayAccessExpression expression, boolean alwaysOutOfBounds) {
}

5
java/java-tests/testData/inspection/dataFlow/fixture/ArrayLength.java
View File

@@ -1,6 +1,11 @@
import java.util.Arrays;
public final class ArrayLength {
void testArrayLengthNonZeroUnknownIndex(int[] arr, int a, int b, int c) {
arr[a+b+c] = 0;
if (<warning descr="Condition 'arr.length == 0' is always 'false'">arr.length == 0</warning>) {}
}
public static void diff(String[] args, String[] args2) {
String[] arr = new String[args2.length - args.length];
if (arr.length > 0) {}