[clang] fix(95366): enhance cast operation safety with LValue validation (PR #95479)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Oleksandr T. (a-tarasyuk)

<details>
<summary>Changes</summary>

Fixes #<!-- -->95366

---
Full diff: https://github.com/llvm/llvm-project/pull/95479.diff


3 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+1) 
- (modified) clang/lib/AST/ExprConstant.cpp (+3) 
- (added) clang/test/Sema/integral-to-ptr.c (+3) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8c2f737836a9d..755557906360b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -847,6 +847,7 @@ Bug Fixes to C++ Support
 - Fixed several bugs in capturing variables within unevaluated contexts. (#GH63845), (#GH67260), (#GH69307),
   (#GH88081), (#GH89496), (#GH90669) and (#GH91633).
 - Fixed handling of brace ellison when building deduction guides. (#GH64625), (#GH83368).
+- Fix an assertion failure caused by non-lvalue usage in lvalue context. (GH95366).
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 7178f081d9cf3..08bee806f172f 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -9325,6 +9325,9 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr *E) {
       Result.IsNullPtr = false;
       return true;
     } else {
+      if (!Value.isLValue())
+        return false;
+
       // Cast is of an lvalue, no need to change value.
       Result.setFrom(Info.Ctx, Value);
       return true;
diff --git a/clang/test/Sema/integral-to-ptr.c b/clang/test/Sema/integral-to-ptr.c
new file mode 100644
index 0000000000000..99f83c3e52057
--- /dev/null
+++ b/clang/test/Sema/integral-to-ptr.c
@@ -0,0 +1,3 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only -std=c11
+
+int x(void) { e: b: ; return &&e - &&b < x; } // expected-warning {{ordered comparison between pointer and integer ('long' and 'int (*)(void)')}}

``````````

</details>


https://github.com/llvm/llvm-project/pull/95479