[SemaCXX] Unconfuse Clang when std::align_val_t is unscoped in C++03linaro-local/ci/tcwg_kernel/llvm-master-arm-next-defconfiglinaro-local/ci/tcwg_kernel/llvm-master-arm-mainline-allyesconfiglinaro-local/ci/tcwg_kernel/llvm-master-aarch64-stable-defconfiglinaro-local/ci/tcwg_kernel/llvm-master-aarch64-lts-allyesconfiglinaro-local/ci/tcwg_kernel/llvm-master-aarch64-lts-allnoconfig

When -faligned-allocation is specified in C++03 libc++ defines
std::align_val_t as an unscoped enumeration type (because Clang didn't
provide scoped enumerations as an extension until 8.0).
Unfortunately Clang confuses the `align_val_t` overloads of delete with
the sized deallocation overloads which aren't enabled. This caused Clang
to call the aligned deallocation function as if it were the sized
deallocation overload.

For example: https://godbolt.org/z/xXJELh

This patch fixes the confusion.

2 files changed, 34 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 22172ba3fb4..8c89a3cee3d 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -1511,11 +1511,19 @@ namespace {
         Destroying = true;
         ++NumBaseParams;
       }
-      if (FD->getNumParams() == NumBaseParams + 2)
-        HasAlignValT = HasSizeT = true;
-      else if (FD->getNumParams() == NumBaseParams + 1) {
-        HasSizeT = FD->getParamDecl(NumBaseParams)->getType()->isIntegerType();
-        HasAlignValT = !HasSizeT;
+
+      if (NumBaseParams < FD->getNumParams() &&
+          S.Context.hasSameUnqualifiedType(
+              FD->getParamDecl(NumBaseParams)->getType(),
+              S.Context.getSizeType())) {
+        ++NumBaseParams;
+        HasSizeT = true;
+      }
+
+      if (NumBaseParams < FD->getNumParams() &&
+          FD->getParamDecl(NumBaseParams)->getType()->isAlignValT()) {
+        ++NumBaseParams;
+        HasAlignValT = true;
       }
 
       // In CUDA, determine how much we'd like / dislike to call this.
diff --git a/clang/test/SemaCXX/cxx03-aligned-allocation-unscoped-enum.cpp b/clang/test/SemaCXX/cxx03-aligned-allocation-unscoped-enum.cpp
new file mode 100644
index 00000000000..7237fbf9db7
--- /dev/null
+++ b/clang/test/SemaCXX/cxx03-aligned-allocation-unscoped-enum.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -std=c++03 -triple x86_64-pc-linux-gnu %s \
+// RUN:   -faligned-allocation -emit-llvm -o - -Wno-c++11-extensions | FileCheck %s
+
+// Ensure Clang doesn't confuse std::align_val_t with the sized deallocation
+// parameter when the enum type is unscoped. Libc++ does this in C++03 in order
+// to support aligned allocation in that dialect.
+
+using size_t = __decltype(sizeof(0));
+
+namespace std {
+enum align_val_t : size_t {};
+}
+_Static_assert(__is_same(__underlying_type(std::align_val_t), size_t), "");
+
+// CHECK-LABEL: define void @_Z1fPi(
+void f(int *p) {
+  // CHECK-NOT: call void @_ZdlPvSt11align_val_t(
+  // CHECK: call void @_ZdlPv(
+  // CHECK: ret void
+  delete p;
+}