[llvm-branch-commits] [clang] release/21.x: [Analysis] Prevent revisiting block when searching for noreturn vars (#150582) (PR #151381)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/151381

Backport 330b40e11fd20e9a29b9c24de17e4ba23afeedc6

Requested by: @pawosm-arm

>From f0b310b07873d3a21ab8f9f0ca137e876fc0f4ec Mon Sep 17 00:00:00 2001
From: Serge Pavlov <sepavloff at gmail.com>
Date: Wed, 30 Jul 2025 20:40:07 +0700
Subject: [PATCH] [Analysis] Prevent revisiting block when searching for
 noreturn vars (#150582)

When searching for noreturn variable initializations, do not visit CFG
blocks that are already visited, it prevents hanging the analysis.

It must fix https://github.com/llvm/llvm-project/issues/150336.

(cherry picked from commit 330b40e11fd20e9a29b9c24de17e4ba23afeedc6)
---
 clang/lib/Sema/AnalysisBasedWarnings.cpp  |  4 ++++
 clang/test/SemaCXX/noreturn-weverything.c | 15 +++++++++++++++
 2 files changed, 19 insertions(+)
 create mode 100644 clang/test/SemaCXX/noreturn-weverything.c

diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 5e75c64eb2b9a..85ac3c06ec2c2 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -503,8 +503,12 @@ static bool areAllValuesNoReturn(const VarDecl *VD, const CFGBlock &VarBlk,
 
   TransferFunctions TF(VD);
   BackwardDataflowWorklist Worklist(*AC.getCFG(), AC);
+  llvm::DenseSet<const CFGBlock *> Visited;
   Worklist.enqueueBlock(&VarBlk);
   while (const CFGBlock *B = Worklist.dequeue()) {
+    if (Visited.contains(B))
+      continue;
+    Visited.insert(B);
     // First check the current block.
     for (CFGBlock::const_reverse_iterator ri = B->rbegin(), re = B->rend();
          ri != re; ++ri) {
diff --git a/clang/test/SemaCXX/noreturn-weverything.c b/clang/test/SemaCXX/noreturn-weverything.c
new file mode 100644
index 0000000000000..92a587d395639
--- /dev/null
+++ b/clang/test/SemaCXX/noreturn-weverything.c
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only %s -Weverything
+
+void free(void *);
+typedef void (*set_free_func)(void *);
+struct Method {
+  int nparams;
+  int *param;
+};
+void selelem_free_method(struct Method* method, void* data) {
+    set_free_func free_func = 0;
+    for (int i = 0; i < method->nparams; ++i)
+        free(&method->param[i]);
+    if (data && free_func)
+        free_func(data);
+}