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Merge pull request #17988 from owen-mc/java/fix-unreachable-blocks-in-const-switch-stmt

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Java: fix unreachable basic blocks in const switch stmt
This commit is contained in:
Owen Mansel-Chan
2024-11-19 00:48:12 +00:00
committed by GitHub
parent c5bec1cc7f ba239a1be0
commit e2f17c63d7
3 changed files with 12 additions and 7 deletions
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4
java/ql/lib/change-notes/2024-11-14-unreachable-basic-block-in-constant-switch-statement.md Normal file
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@@ -0,0 +1,4 @@
---
category: minorAnalysis
---
* In a switch statement with a constant switch expression, all non-matching cases were being marked as unreachable, including those that can be reached by falling through from the matching case. This has now been fixed.

14
java/ql/lib/semmle/code/java/controlflow/UnreachableBlocks.qll
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@@ -217,13 +217,15 @@ class UnreachableBasicBlock extends BasicBlock {
not this instanceof CatchClause not this instanceof CatchClause
or or
// Switch statements with a constant comparison expression may have unreachable cases. // Switch statements with a constant comparison expression may have unreachable cases.
exists(ConstSwitchStmt constSwitchStmt, BasicBlock failingCaseBlock | exists(ConstSwitchStmt constSwitchStmt, BasicBlock unreachableCaseBlock |
failingCaseBlock = constSwitchStmt.getAFailingCase().getBasicBlock() // Not accessible from the switch expression
| unreachableCaseBlock = constSwitchStmt.getAFailingCase().getBasicBlock() and
// Not accessible from the successful case // Not accessible from the successful case
not constSwitchStmt.getMatchingCase().getBasicBlock().getABBSuccessor*() = failingCaseBlock and not constSwitchStmt.getMatchingCase().getBasicBlock().getABBSuccessor*() =
// Blocks dominated by the failing case block are unreachable unreachableCaseBlock
constSwitchStmt.getAFailingCase().getBasicBlock().bbDominates(this) |
// Blocks dominated by an unreachable case block are unreachable
unreachableCaseBlock.bbDominates(this)
) )
} }
} }

1
java/ql/test/library-tests/unreachableblocks/UnreachableBlocks.expected
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@@ -3,7 +3,6 @@
| unreachableblocks/Unreachable.java:12:22:14:3 | { ... } | | unreachableblocks/Unreachable.java:12:22:14:3 | { ... } |
| unreachableblocks/Unreachable.java:17:3:17:9 | case ... | | unreachableblocks/Unreachable.java:17:3:17:9 | case ... |
| unreachableblocks/Unreachable.java:19:3:19:9 | case ... | | unreachableblocks/Unreachable.java:19:3:19:9 | case ... |
| unreachableblocks/Unreachable.java:22:3:22:9 | case ... |
| unreachableblocks/Unreachable.java:24:3:24:9 | case ... | | unreachableblocks/Unreachable.java:24:3:24:9 | case ... |
| unreachableblocks/Unreachable.java:26:3:26:10 | case ... | | unreachableblocks/Unreachable.java:26:3:26:10 | case ... |
| unreachableblocks/Unreachable.java:27:3:27:10 | default | | unreachableblocks/Unreachable.java:27:3:27:10 | default |