[clang] [Clang] Prevent null pointer dereference in Sema::CodeCompleteQualifi… (PR #90490)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (smanna12)

<details>
<summary>Changes</summary>

…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
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())));
+      }
     }
   }
 

``````````

</details>


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