[clang] [Clang] Fix missing -Warray-bounds warning on member function calls. (PR #179647)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Prajwal P J (pjalwadi)

<details>
<summary>Changes</summary>

Fixes #<!-- -->179128.
This patch fixes a false negative where Clang failed to detect out-of-bounds access when calling a member function on an invalid array index. It adds handling for CXXMemberCallExpr in CheckArrayAccess.

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Full diff: https://github.com/llvm/llvm-project/pull/179647.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaChecking.cpp (+4) 
- (modified) clang/test/SemaCXX/constant-expression-cxx2a.cpp (+3-2) 


``````````diff
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 3f19b6ad16c13..cec6060cc9dab 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -15449,6 +15449,10 @@ void Sema::CheckArrayAccess(const Expr *expr) {
         expr = cast<MemberExpr>(expr)->getBase();
         break;
       }
+      case Stmt::CXXMemberCallExprClass: {
+        expr = cast<CXXMemberCallExpr>(expr)->getImplicitObjectArgument();
+        break;
+      }
       case Stmt::ArraySectionExprClass: {
         const ArraySectionExpr *ASE = cast<ArraySectionExpr>(expr);
         // FIXME: We should probably be checking all of the elements to the
diff --git a/clang/test/SemaCXX/constant-expression-cxx2a.cpp b/clang/test/SemaCXX/constant-expression-cxx2a.cpp
index 4fcd243b4442c..75be84557a0ec 100644
--- a/clang/test/SemaCXX/constant-expression-cxx2a.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx2a.cpp
@@ -1241,8 +1241,9 @@ namespace dtor_call {
   }
 
   constexpr void destroy_past_end_array() { // expected-error {{never produces a constant expression}}
-    A a[2];
-    a[2].~A(); // expected-note {{destruction of dereferenced one-past-the-end pointer}}
+  A a[2]; // expected-note {{array 'a' declared here}}
+  a[2].~A(); // expected-note {{destruction of dereferenced one-past-the-end pointer}} \
+             // expected-warning {{array index 2 is past the end of the array}}
   }
 
   union As {

``````````

</details>


https://github.com/llvm/llvm-project/pull/179647