[clang] Pointer dereference collapse loop2 (PR #203252)

[Zahira Ammarguellat via cfe-commits]

https://github.com/zahiraam updated https://github.com/llvm/llvm-project/pull/203252

>From 0235cace0638619b1631cd17c8504e5406da3563 Mon Sep 17 00:00:00 2001
From: Ammarguellat <zahira.ammarguellat at intel.com>
Date: Thu, 11 Jun 2026 05:16:12 -0700
Subject: [PATCH 1/2] [OpenMP] Pointer dereference collapse loop

---
 clang/lib/Sema/SemaOpenMP.cpp                   |  2 +-
 clang/test/OpenMP/collapse_extern_ref_crash.cpp | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/OpenMP/collapse_extern_ref_crash.cpp

diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 113c8f3cb3016..79a0c396f787e 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -8044,7 +8044,7 @@ class ForSubExprChecker : public DynamicRecursiveASTVisitor {
     VarDecl *V = VD->getPotentiallyDecomposedVarDecl();
     if (V->getType()->isReferenceType()) {
       VarDecl *VD = V->getDefinition();
-      if (VD->hasInit()) {
+      if (VD && VD->hasInit()) {
         Expr *I = VD->getInit();
         DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(I);
         if (!DRE)
diff --git a/clang/test/OpenMP/collapse_extern_ref_crash.cpp b/clang/test/OpenMP/collapse_extern_ref_crash.cpp
new file mode 100644
index 0000000000000..4cc1a56115c73
--- /dev/null
+++ b/clang/test/OpenMP/collapse_extern_ref_crash.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -verify -fopenmp -fopenmp-version=51 %s
+// RUN: %clang_cc1 -verify -fopenmp-simd -fopenmp-version=51 %s
+
+// Verify no crash when collapsing a loop nest where the induction variable
+// is an extern reference type. PR/issue: null dereference in getInitLCDecl
+// when VarDecl::getDefinition() returns nullptr.
+
+extern int &dim;
+auto test() {
+  // expected-error at +1 {{expected-error for malformed collapse}}
+#pragma omp parallel for collapse(2)
+  for (int i = 0; i < dim; ++i) {
+    for (i = 0; i < 10; i++) {
+      int dummy;
+    }
+  }
+}

>From 00a3b74fff37be67beb6cd2b09fb9f734ca426ee Mon Sep 17 00:00:00 2001
From: Ammarguellat <zahira.ammarguellat at intel.com>
Date: Thu, 11 Jun 2026 05:43:06 -0700
Subject: [PATCH 2/2] Fixed LIT test

---
 clang/test/OpenMP/collapse_extern_ref_crash.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang/test/OpenMP/collapse_extern_ref_crash.cpp b/clang/test/OpenMP/collapse_extern_ref_crash.cpp
index 4cc1a56115c73..432fd91ef5852 100644
--- a/clang/test/OpenMP/collapse_extern_ref_crash.cpp
+++ b/clang/test/OpenMP/collapse_extern_ref_crash.cpp
@@ -1,13 +1,14 @@
 // RUN: %clang_cc1 -verify -fopenmp -fopenmp-version=51 %s
 // RUN: %clang_cc1 -verify -fopenmp-simd -fopenmp-version=51 %s
 
+// expected-no-diagnostics
+
 // Verify no crash when collapsing a loop nest where the induction variable
 // is an extern reference type. PR/issue: null dereference in getInitLCDecl
 // when VarDecl::getDefinition() returns nullptr.
 
 extern int &dim;
 auto test() {
-  // expected-error at +1 {{expected-error for malformed collapse}}
 #pragma omp parallel for collapse(2)
   for (int i = 0; i < dim; ++i) {
     for (i = 0; i < 10; i++) {