[LifetimeSafety] Handle pruned-edges (null blocks) in dataflow #150670
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@llvm/pr-subscribers-clang-temporal-safety @llvm/pr-subscribers-clang-analysis Author: Utkarsh Saxena (usx95) ChangesFix a crash in the lifetime safety dataflow analysis when handling null CFG blocks. Added a null check for adjacent blocks in the dataflow analysis algorithm to prevent dereferencing null pointers. This occurs when processing CFG blocks with unreachable successors or predecessors. Original crash: https://compiler-explorer.com/z/qfzfqG5vM Fixes #150095 Full diff: https://github.com/llvm/llvm-project/pull/150670.diff 2 Files Affected:
diff --git a/clang/lib/Analysis/LifetimeSafety.cpp b/clang/lib/Analysis/LifetimeSafety.cpp
index 94b8197bbf6f3..f39998cca56fe 100644
--- a/clang/lib/Analysis/LifetimeSafety.cpp
+++ b/clang/lib/Analysis/LifetimeSafety.cpp
@@ -603,6 +603,8 @@ class DataflowAnalysis {
OutStates[B] = StateOut;
Visited.set(B->getBlockID());
for (const CFGBlock *AdjacentB : isForward() ? B->succs() : B->preds()) {
+ if (!AdjacentB)
+ continue;
Lattice OldInState = getInState(AdjacentB);
Lattice NewInState = D.join(OldInState, StateOut);
// Enqueue the adjacent block if its in-state has changed or if we have
diff --git a/clang/unittests/Analysis/LifetimeSafetyTest.cpp b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
index a48dc45e4f806..7cd679e184f6c 100644
--- a/clang/unittests/Analysis/LifetimeSafetyTest.cpp
+++ b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
@@ -512,6 +512,25 @@ TEST_F(LifetimeAnalysisTest, PointersAndExpirationInACycle) {
EXPECT_THAT(LoansTo({"temp"}), AreExpiredAt("after_loop"));
}
+TEST_F(LifetimeAnalysisTest, InfiniteLoopPrunesEdges) {
+ SetupTest(R"(
+ void target(MyObj out) {
+ MyObj *p = &out;
+ POINT(before_loop);
+
+ for (;;) {
+ POINT(begin);
+ MyObj in;
+ p = ∈
+ POINT(end);
+ }
+ }
+ )");
+ EXPECT_THAT(Origin("p"), HasLoansTo({"out"}, "before_loop"));
+ EXPECT_THAT(Origin("p"), HasLoansTo({"in", "out"}, "begin"));
+ EXPECT_THAT(Origin("p"), HasLoansTo({"in"}, "end"));
+}
+
TEST_F(LifetimeAnalysisTest, NestedScopes) {
SetupTest(R"(
void target() {
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Xazax-hun
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Jul 25, 2025
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Fix a crash in the lifetime safety dataflow analysis when handling null CFG blocks.
Added a null check for adjacent blocks in the dataflow analysis algorithm to prevent dereferencing null pointers. This occurs when processing CFG blocks with unreachable successors or predecessors.
Original crash: https://compiler-explorer.com/z/qfzfqG5vM
Fixes #150095