[llvm-branch-commits] [clang] [Clang][Backport] Fix handling of reference types in tryEvaluateBuiltinObjectSize (#138247) (PR #139579)

[via llvm-branch-commits]

https://github.com/cor3ntin created https://github.com/llvm/llvm-project/pull/139579

The order of operation was slightly incorrect, as we were checking for incomplete types *before* handling reference types.

Fixes #129397

---------

>From 814e1d2a1762edee3f04346cbcd18bd3fad23aec Mon Sep 17 00:00:00 2001
From: cor3ntin <corentinjabot at gmail.com>
Date: Fri, 2 May 2025 18:45:24 +0200
Subject: [PATCH] [Clang] Fix handling of reference types in
 tryEvaluateBuiltinObjectSize (#138247)

The order of operation was slightly incorrect, as we were checking for
incomplete types *before* handling reference types.

Fixes #129397

---------

Co-authored-by: Erich Keane <ekeane at nvidia.com>
---
 clang/lib/AST/ExprConstant.cpp                   |  8 +++++---
 clang/test/SemaCXX/builtin-object-size-cxx14.cpp | 12 ++++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 5aae78dd2fee7..23602362eaa79 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -12710,11 +12710,13 @@ static bool determineEndOffset(EvalInfo &Info, SourceLocation ExprLoc,
   bool DetermineForCompleteObject = refersToCompleteObject(LVal);
 
   auto CheckedHandleSizeof = [&](QualType Ty, CharUnits &Result) {
-    if (Ty.isNull() || Ty->isIncompleteType() || Ty->isFunctionType())
+    if (Ty.isNull())
       return false;
 
-    if (Ty->isReferenceType())
-      Ty = Ty.getNonReferenceType();
+    Ty = Ty.getNonReferenceType();
+
+    if (Ty->isIncompleteType() || Ty->isFunctionType())
+      return false;
 
     return HandleSizeof(Info, ExprLoc, Ty, Result);
   };
diff --git a/clang/test/SemaCXX/builtin-object-size-cxx14.cpp b/clang/test/SemaCXX/builtin-object-size-cxx14.cpp
index b7c6f6be01f54..fdd3cb7af088f 100644
--- a/clang/test/SemaCXX/builtin-object-size-cxx14.cpp
+++ b/clang/test/SemaCXX/builtin-object-size-cxx14.cpp
@@ -1,5 +1,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify=expected,cxx14 -std=c++14 %s
 // RUN: %clang_cc1 -fsyntax-only -verify -std=c++2a %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++2b %s
+
 
 typedef __SIZE_TYPE__ size_t;
 
@@ -119,3 +121,13 @@ constexpr int bos_new() { // cxx14-error {{constant expression}}
   void *p = new int; // cxx14-note {{until C++20}}
   return __builtin_object_size(p, 0);
 }
+
+
+namespace GH129397 {
+
+struct incomplete;
+void test(incomplete &ref) {
+  __builtin_object_size(&ref, 1);
+}
+
+}