Extend the C++03 definition of POD to include defaulted functions

The AST/conditionally-trivial-smfs tests look a bit questionable, but
are consistent with GCC's POD-ness, at least as far as packing is
concerned: https://godbolt.org/z/36nqPMbKM
(questionable because it looks like the type would be non-copyable, so
how could it be pod? But the calling convention/pass by value seems to
work correctly (local testing verifies that this behavior is preserved
even with this patch: https://godbolt.org/z/3Pa89zsv6 ))

Differential Revision: https://reviews.llvm.org/D119051

diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
index cfa9832..a790385 100644 (file)
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -229,6 +229,7 @@ public:
     /// This causes clang to:
     ///   - Reverse the implementation for DR692, DR1395 and DR1432.
     ///   - pack non-POD members of packed structs.
+    ///   - consider classes with defaulted special member functions non-pod.
     Ver15,
 
     /// Conform to the underlying platform's C and C++ ABIs as closely

diff --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
index 9b9439e..2c50b19 100644 (file)
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -1566,6 +1566,14 @@ public:
 
   virtual CallingConvKind getCallingConvKind(bool ClangABICompat4) const;
 
+  /// Controls whether explicitly defaulted (`= default`) special member
+  /// functions disqualify something from being POD-for-the-purposes-of-layout.
+  /// Historically, Clang didn't consider these acceptable for POD, but GCC
+  /// does. So in newer Clang ABIs they are acceptable for POD to be compatible
+  /// with GCC/Itanium ABI, and remains disqualifying for targets that need
+  /// Clang backwards compatibility rather than GCC/Itanium ABI compatibility.
+  virtual bool areDefaultedSMFStillPOD(const LangOptions&) const;
+
   /// Controls if __builtin_longjmp / __builtin_setjmp can be lowered to
   /// llvm.eh.sjlj.longjmp / llvm.eh.sjlj.setjmp.
   virtual bool hasSjLjLowering() const {

diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index b922109..16b2139 100644 (file)
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -36,6 +36,7 @@
 #include "clang/Basic/PartialDiagnostic.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/Specifiers.h"
+#include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
@@ -768,12 +769,16 @@ void CXXRecordDecl::addedMember(Decl *D) {
         // Note that we have a user-declared constructor.
         data().UserDeclaredConstructor = true;
 
-        // C++ [class]p4:
-        //   A POD-struct is an aggregate class [...]
-        // Since the POD bit is meant to be C++03 POD-ness, clear it even if
-        // the type is technically an aggregate in C++0x since it wouldn't be
-        // in 03.
-        data().PlainOldData = false;
+        const TargetInfo &TI = getASTContext().getTargetInfo();
+        if ((!Constructor->isDeleted() && !Constructor->isDefaulted()) ||
+            !TI.areDefaultedSMFStillPOD(getLangOpts())) {
+          // C++ [class]p4:
+          //   A POD-struct is an aggregate class [...]
+          // Since the POD bit is meant to be C++03 POD-ness, clear it even if
+          // the type is technically an aggregate in C++0x since it wouldn't be
+          // in 03.
+          data().PlainOldData = false;
+        }
       }
 
       if (Constructor->isDefaultConstructor()) {
@@ -881,18 +886,24 @@ void CXXRecordDecl::addedMember(Decl *D) {
       if (!Method->isImplicit()) {
         data().UserDeclaredSpecialMembers |= SMKind;
 
-        // C++03 [class]p4:
-        //   A POD-struct is an aggregate class that has [...] no user-defined
-        //   copy assignment operator and no user-defined destructor.
-        //
-        // Since the POD bit is meant to be C++03 POD-ness, and in C++03,
-        // aggregates could not have any constructors, clear it even for an
-        // explicitly defaulted or deleted constructor.
-        // type is technically an aggregate in C++0x since it wouldn't be in 03.
-        //
-        // Also, a user-declared move assignment operator makes a class non-POD.
-        // This is an extension in C++03.
-        data().PlainOldData = false;
+        const TargetInfo &TI = getASTContext().getTargetInfo();
+        if ((!Method->isDeleted() && !Method->isDefaulted() &&
+             SMKind != SMF_MoveAssignment) ||
+            !TI.areDefaultedSMFStillPOD(getLangOpts())) {
+          // C++03 [class]p4:
+          //   A POD-struct is an aggregate class that has [...] no user-defined
+          //   copy assignment operator and no user-defined destructor.
+          //
+          // Since the POD bit is meant to be C++03 POD-ness, and in C++03,
+          // aggregates could not have any constructors, clear it even for an
+          // explicitly defaulted or deleted constructor.
+          // type is technically an aggregate in C++0x since it wouldn't be in
+          // 03.
+          //
+          // Also, a user-declared move assignment operator makes a class
+          // non-POD. This is an extension in C++03.
+          data().PlainOldData = false;
+        }
       }
       // When instantiating a class, we delay updating the destructor and
       // triviality properties of the class until selecting a destructor and

diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 833e37b..8def4be 100644 (file)
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -559,6 +559,10 @@ TargetInfo::getCallingConvKind(bool ClangABICompat4) const {
   return CCK_Default;
 }
 
+bool TargetInfo::areDefaultedSMFStillPOD(const LangOptions &LangOpts) const {
+  return LangOpts.getClangABICompat() > LangOptions::ClangABI::Ver15;
+}
+
 LangAS TargetInfo::getOpenCLTypeAddrSpace(OpenCLTypeKind TK) const {
   switch (TK) {
   case OCLTK_Image:

diff --git a/clang/lib/Basic/Targets/OSTargets.h b/clang/lib/Basic/Targets/OSTargets.h
index 88f7c4a..5f5b461 100644 (file)
--- a/clang/lib/Basic/Targets/OSTargets.h
+++ b/clang/lib/Basic/Targets/OSTargets.h
@@ -161,6 +161,10 @@ public:
                            : TargetInfo::UnsignedLongLong)
                : TargetInfo::getLeastIntTypeByWidth(BitWidth, IsSigned);
   }
+
+  bool areDefaultedSMFStillPOD(const LangOptions &) const override {
+    return false;
+  }
 };
 
 // DragonFlyBSD Target
@@ -558,6 +562,10 @@ public:
   checkCallingConvention(CallingConv CC) const override {
     return (CC == CC_C) ? TargetInfo::CCCR_OK : TargetInfo::CCCR_Error;
   }
+
+  bool areDefaultedSMFStillPOD(const LangOptions &) const override {
+    return false;
+  }
 };
 
 // PS4 Target

diff --git a/clang/test/AST/conditionally-trivial-smfs.cpp b/clang/test/AST/conditionally-trivial-smfs.cpp
index 34db1cd..1dc1f6c 100644 (file)
--- a/clang/test/AST/conditionally-trivial-smfs.cpp
+++ b/clang/test/AST/conditionally-trivial-smfs.cpp
@@ -297,6 +297,7 @@ template struct MoveAssignmentCheck<1>;
 // CHECK-NEXT:          "isAggregate": true,
 // CHECK-NEXT:          "isEmpty": true,
 // CHECK-NEXT:          "isLiteral": true,
+// CHECK-NEXT:          "isPOD": true,
 // CHECK-NEXT:          "isStandardLayout": true,
 // CHECK-NEXT:          "isTrivial": true,
 // CHECK-NEXT:          "isTriviallyCopyable": true,
@@ -316,6 +317,7 @@ template struct MoveAssignmentCheck<2>;
 // CHECK-NEXT:          "isAggregate": true,
 // CHECK-NEXT:          "isEmpty": true,
 // CHECK-NEXT:          "isLiteral": true,
+// CHECK-NEXT:          "isPOD": true,
 // CHECK-NEXT:          "isStandardLayout": true,
 // CHECK-NEXT:          "isTrivial": true,
 // CHECK-NEXT:          "isTriviallyCopyable": true,
@@ -335,6 +337,7 @@ template struct MoveAssignmentCheck<3>;
 // CHECK-NEXT:          "isAggregate": true,
 // CHECK-NEXT:          "isEmpty": true,
 // CHECK-NEXT:          "isLiteral": true,
+// CHECK-NEXT:          "isPOD": true,
 // CHECK-NEXT:          "isStandardLayout": true,
 // CHECK-NEXT:          "moveAssign": {
 // CHECK-NEXT:            "exists": true,

diff --git a/clang/test/SemaCXX/class-layout.cpp b/clang/test/SemaCXX/class-layout.cpp
index f3106ec..3d710dc 100644 (file)
--- a/clang/test/SemaCXX/class-layout.cpp
+++ b/clang/test/SemaCXX/class-layout.cpp
@@ -1,10 +1,12 @@
-// RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++98 -Wno-inaccessible-base
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++98 -Wno-inaccessible-base -Wno-c++11-extensions
 // RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base
 // RUN: %clang_cc1 -triple x86_64-apple-darwin    %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -DCLANG_ABI_COMPAT=15
 // RUN: %clang_cc1 -triple x86_64-scei-ps4        %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -DCLANG_ABI_COMPAT=6
 // RUN: %clang_cc1 -triple x86_64-sie-ps5         %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -DCLANG_ABI_COMPAT=6
 // RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=6 -DCLANG_ABI_COMPAT=6
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=14 -DCLANG_ABI_COMPAT=14
 // RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=15 -DCLANG_ABI_COMPAT=15
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown %s -fsyntax-only -verify -std=c++11 -Wno-inaccessible-base -fclang-abi-compat=16 -DCLANG_ABI_COMPAT=16
 // expected-no-diagnostics
 
 #define SA(n, p) int a##n[(p) ? 1 : -1]
@@ -656,3 +658,25 @@ struct C {
 _Static_assert(__builtin_offsetof(C, b) == 3, "");
 }
 
+namespace cxx11_pod {
+struct t1 {
+  t1() = default;
+  t1(const t1&) = delete;
+  ~t1() = delete;
+  t1(t1&&) = default;
+  int a;
+  char c;
+};
+struct t2 {
+  t1 v1;
+} __attribute__((packed));
+_Static_assert(_Alignof(t2) == 1, "");
+struct t3 : t1 {
+  char c;
+};
+#if defined(CLANG_ABI_COMPAT) && CLANG_ABI_COMPAT <= 15
+_Static_assert(sizeof(t3) == 8, "");
+#else
+_Static_assert(sizeof(t3) == 12, "");
+#endif
+}