[clang] 874ca08 - [Clang][ExprConstant] fix constant expression did not evaluate to integer (#97146)

[via cfe-commits]

Author: Zhikai Zeng
Date: 2024-07-06T16:28:23+08:00
New Revision: 874ca08645420413e525054a47caf039bebde28b

URL: https://github.com/llvm/llvm-project/commit/874ca08645420413e525054a47caf039bebde28b
DIFF: https://github.com/llvm/llvm-project/commit/874ca08645420413e525054a47caf039bebde28b.diff

LOG: [Clang][ExprConstant] fix constant expression did not evaluate to integer (#97146)

fixes https://github.com/llvm/llvm-project/issues/96670

The cause is that we might return a lvalue here at


https://github.com/llvm/llvm-project/blob/3e53c97d33210db68188e731e93ee48dbaeeae32/clang/lib/AST/ExprConstant.cpp#L15861-L15865

This PR will make sure we return a rvalue in `FastEvaluateAsRValue`.

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/AST/ExprConstant.cpp
    clang/test/SemaCXX/eval-crashes.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f6431a76b38de..d60c6fbf15d56 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -967,6 +967,8 @@ Bug Fixes to C++ Support
 - Fixed an assertion failure about invalid conversion when calling lambda. (#GH96205).
 - Fixed a bug where the first operand of binary ``operator&`` would be transformed as if it was the operand
   of the address of operator. (#GH97483).
+- Fixed an assertion failure about a constant expression which is a known integer but is not
+  evaluated to an integer. (#GH96670).
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

diff  --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 374a3acf7aa26..e0c9ef68cb448 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -15859,9 +15859,12 @@ static bool FastEvaluateAsRValue(const Expr *Exp, Expr::EvalResult &Result,
 
   if (const auto *CE = dyn_cast<ConstantExpr>(Exp)) {
     if (CE->hasAPValueResult()) {
-      Result.Val = CE->getAPValueResult();
-      IsConst = true;
-      return true;
+      APValue APV = CE->getAPValueResult();
+      if (!APV.isLValue()) {
+        Result.Val = std::move(APV);
+        IsConst = true;
+        return true;
+      }
     }
 
     // The SubExpr is usually just an IntegerLiteral.

diff  --git a/clang/test/SemaCXX/eval-crashes.cpp b/clang/test/SemaCXX/eval-crashes.cpp
index 017df977b26b7..0865dafe4bf92 100644
--- a/clang/test/SemaCXX/eval-crashes.cpp
+++ b/clang/test/SemaCXX/eval-crashes.cpp
@@ -61,3 +61,13 @@ struct array {
   array() : data(*new int[1][2]) {}
 };
 }
+
+namespace GH96670 {
+inline constexpr long ullNil = -1;
+
+template<typename T = long, const T &Nil = ullNil>
+struct Test {};
+
+inline constexpr long lNil = -1;
+Test<long, lNil> c;
+}