[Clang] Prevent null pointer dereference in Sema::​CodeCompleteQualifiedId()

[smanna12]

The null pointer dereference issue seems happening with in the expression NNS->getAsType().

Although dyn_cast_or_null() correctly handles null pointers, it doesn’t prevent the subsequent dereferencing operation.

The fix ensures that NNS pointer is not null before calling the getAsType() method, thus preventing potential runtime errors caused by attempting to access a null pointer.

[llvmbot]

@llvm/pr-subscribers-clang

Author: None (smanna12)

Changes

…edId()

The null pointer dereference issue seems happening with in the expression NNS->getAsType().

Although dyn_cast_or_null<TemplateTypeParmType>() correctly handles null pointers, it doesn’t prevent the subsequent dereferencing operation.

The fix ensures that NNS pointer is not null before calling the getAsType() method, thus preventing potential runtime errors caused by attempting to access a null pointer.

---

Full diff: https://github.com/llvm/llvm-project/pull/90490.diff

1 Files Affected:

• (modified) clang/lib/Sema/SemaCodeComplete.cpp (+10-8)

diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
index c335017f243eb2..3f0ab10646fe5d 100644
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -6714,14 +6714,16 @@ void Sema::CodeCompleteQualifiedId(Scope *S, CXXScopeSpec &SS,
 
   // If the scope is a concept-constrained type parameter, infer nested
   // members based on the constraints.
-  if (const auto *TTPT =
-          dyn_cast_or_null<TemplateTypeParmType>(NNS->getAsType())) {
-    for (const auto &R : ConceptInfo(*TTPT, S).members()) {
-      if (R.Operator != ConceptInfo::Member::Colons)
-        continue;
-      Results.AddResult(CodeCompletionResult(
-          R.render(*this, CodeCompleter->getAllocator(),
-                   CodeCompleter->getCodeCompletionTUInfo())));
+  if (NNS) {
+    if (const auto *TTPT =
+            dyn_cast_or_null<TemplateTypeParmType>(NNS->getAsType())) {
+      for (const auto &R : ConceptInfo(*TTPT, S).members()) {
+        if (R.Operator != ConceptInfo::Member::Colons)
+          continue;
+        Results.AddResult(CodeCompletionResult(
+            R.render(*this, CodeCompleter->getAllocator(),
+                     CodeCompleter->getCodeCompletionTUInfo())));
+      }
     }
   }
 

[shafik]

Looks good, I will let Tom make the final accept.

[tahonermann]

Adding Sam McCall as an additional reviewer since he originally authored this code in commit a76e68c.

[tahonermann]

The change looks good to me. I recommend giving @sam-mccall a day or so to comment if he wants to.

[smanna12]

Thanks @tahonermann for reviews!

[smanna12]

@sam-mccall, could you please review/comment on the fix? Thank you

[smanna12]

I will followup any comments from @sam-mccall in a separate PR. Merging this PR. Thanks everyone for reviews!