[Clang] Correctly handle allocation in template arguments

Fixes #62462 Reviewed By: #clang-language-wg, erichkeane Differential Revision: https://reviews.llvm.org/D150036
llvm · May 8, 2023 · 9857caf · 9857caf
1 parent 1d21d2e
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Showing 3 changed files with 37 additions and 3 deletions.
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
@@ -370,7 +370,7 @@ Bug Fixes in This Version
   (`#62192 <https://github.com/llvm/llvm-project/issues/62192>`_)
 - Fix crash when attempting to pass a non-pointer type as first argument of
   ``__builtin_assume_aligned``.
-  (`#62305 <https://github.com/llvm/llvm-project/issues/62305>`_) 
+  (`#62305 <https://github.com/llvm/llvm-project/issues/62305>`_)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -416,6 +416,8 @@ Bug Fixes to C++ Support
   initialization.
   (`#61567 <https://github.com/llvm/llvm-project/issues/61567>`_)
 - Fix a crash when expanding a pack as the index of a subscript expression.
+- Fix handling of constexpr dynamic memory allocations in template
+  arguments. (`#62462 <https://github.com/llvm/llvm-project/issues/62462>`_)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
@@ -15354,8 +15354,16 @@ bool Expr::EvaluateAsConstantExpr(EvalResult &Result, const ASTContext &Ctx,
   LValue LVal;
   LVal.set(Base);
 
-  if (!::EvaluateInPlace(Result.Val, Info, LVal, this) || Result.HasSideEffects)
-    return false;
+  {
+    // C++23 [intro.execution]/p5
+    // A full-expression is [...] a constant-expression
+    // So we need to make sure temporary objects are destroyed after having
+    // evaluating the expression (per C++23 [class.temporary]/p4).
+    FullExpressionRAII Scope(Info);
+    if (!::EvaluateInPlace(Result.Val, Info, LVal, this) ||
+        Result.HasSideEffects || !Scope.destroy())
+      return false;
+  }
 
   if (!Info.discardCleanups())
     llvm_unreachable("Unhandled cleanup; missing full expression marker?");

diff --git a/clang/test/SemaCXX/cxx2a-constexpr-dynalloc.cpp b/clang/test/SemaCXX/cxx2a-constexpr-dynalloc.cpp
@@ -215,3 +215,27 @@ namespace PR48606 {
   }
   static_assert(h());
 }
+
+namespace GH62462 {
+
+class string {
+public:
+  char *mem;
+  constexpr string() {
+    this->mem = new char(1);
+  }
+  constexpr ~string() {
+    delete this->mem;
+  }
+  constexpr unsigned size() const { return 4; }
+};
+
+
+template <unsigned N>
+void test() {};
+
+void f() {
+    test<string().size()>();
+}
+
+}