[clang] Enable sized deallocation by default in C++14 onwards (#83774)

Since C++14 has been released for about nine years and most standard
libraries have implemented sized deallocation functions, it's time to
make this feature default again.

This is another try of https://reviews.llvm.org/D112921.

Fixes #60061

clang-tools-extra/clangd/unittests/FindTargetTests.cpp

@@ -839,7 +839,9 @@ TEST_F(TargetDeclTest, OverloadExpr) {
       [[delete]] x;
     }
   )cpp";
-  EXPECT_DECLS("CXXDeleteExpr", "void operator delete(void *) noexcept");
+  // Sized deallocation is enabled by default in C++14 onwards.
+  EXPECT_DECLS("CXXDeleteExpr",
+               "void operator delete(void *, unsigned long) noexcept");
 }
 
 TEST_F(TargetDeclTest, DependentExprs) {

clang-tools-extra/test/clang-tidy/checkers/misc/new-delete-overloads.cpp

@@ -12,16 +12,6 @@ struct S {
 // CHECK-MESSAGES: :[[@LINE+1]]:7: warning: declaration of 'operator new' has no matching declaration of 'operator delete' at the same scope
 void *operator new(size_t size) noexcept(false);
 
-struct T {
-  // Sized deallocations are not enabled by default, and so this new/delete pair
-  // does not match. However, we expect only one warning, for the new, because
-  // the operator delete is a placement delete and we do not warn on mismatching
-  // placement operations.
-  // CHECK-MESSAGES: :[[@LINE+1]]:9: warning: declaration of 'operator new' has no matching declaration of 'operator delete' at the same scope
-  void *operator new(size_t size) noexcept;
-  void operator delete(void *ptr, size_t) noexcept; // ok only if sized deallocation is enabled
-};
-
 struct U {
   void *operator new(size_t size) noexcept;
   void operator delete(void *ptr) noexcept;

clang/docs/ReleaseNotes.rst

@@ -90,6 +90,11 @@ C++ Language Changes
 --------------------
 - Implemented ``_BitInt`` literal suffixes ``__wb`` or ``__WB`` as a Clang extension with ``unsigned`` modifiers also allowed. (#GH85223).
 
+C++14 Feature Support
+^^^^^^^^^^^^^^^^^^^^^
+- Sized deallocation is enabled by default in C++14 onwards. The user may specify
+  ``-fno-sized-deallocation`` to disable it if there are some regressions.
+
 C++20 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
 

clang/include/clang/Driver/Options.td

@@ -603,6 +603,7 @@ class MarshallingInfoVisibility<KeyPathAndMacro kpm, code default>
 // Key paths that are constant during parsing of options with the same key path prefix.
 defvar cplusplus = LangOpts<"CPlusPlus">;
 defvar cpp11 = LangOpts<"CPlusPlus11">;
+defvar cpp14 = LangOpts<"CPlusPlus14">;
 defvar cpp17 = LangOpts<"CPlusPlus17">;
 defvar cpp20 = LangOpts<"CPlusPlus20">;
 defvar c99 = LangOpts<"C99">;
@@ -3370,10 +3371,9 @@ defm relaxed_template_template_args : BoolFOption<"relaxed-template-template-arg
           "Enable C++17 relaxed template template argument matching">,
   NegFlag<SetFalse>>;
 defm sized_deallocation : BoolFOption<"sized-deallocation",
-  LangOpts<"SizedDeallocation">, DefaultFalse,
-  PosFlag<SetTrue, [], [ClangOption, CC1Option],
-          "Enable C++14 sized global deallocation functions">,
-  NegFlag<SetFalse>>;
+  LangOpts<"SizedDeallocation">, Default<cpp14.KeyPath>,
+  PosFlag<SetTrue, [], [], "Enable C++14 sized global deallocation functions">,
+  NegFlag<SetFalse>, BothFlags<[], [ClangOption, CC1Option]>>;
 defm aligned_allocation : BoolFOption<"aligned-allocation",
   LangOpts<"AlignedAllocation">, Default<cpp17.KeyPath>,
   PosFlag<SetTrue, [], [ClangOption], "Enable C++17 aligned allocation functions">,

clang/lib/Driver/ToolChains/Clang.cpp

@@ -7262,10 +7262,15 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.addOptInFlag(CmdArgs, options::OPT_frelaxed_template_template_args,
                     options::OPT_fno_relaxed_template_template_args);
 
-  // -fsized-deallocation is off by default, as it is an ABI-breaking change for
-  // most platforms.
-  Args.addOptInFlag(CmdArgs, options::OPT_fsized_deallocation,
-                    options::OPT_fno_sized_deallocation);
+  // -fsized-deallocation is on by default in C++14 onwards and otherwise off
+  // by default.
+  if (Arg *A = Args.getLastArg(options::OPT_fsized_deallocation,
+                               options::OPT_fno_sized_deallocation)) {
+    if (A->getOption().matches(options::OPT_fno_sized_deallocation))
+      CmdArgs.push_back("-fno-sized-deallocation");
+    else
+      CmdArgs.push_back("-fsized-deallocation");
+  }
 
   // -faligned-allocation is on by default in C++17 onwards and otherwise off
   // by default.

clang/lib/Driver/ToolChains/Darwin.cpp

@@ -2912,16 +2912,68 @@ static bool sdkSupportsBuiltinModules(const Darwin::DarwinPlatformKind &TargetPl
   }
 }
 
-void Darwin::addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
-                                   llvm::opt::ArgStringList &CC1Args,
-                                   Action::OffloadKind DeviceOffloadKind) const {
+static inline llvm::VersionTuple
+sizedDeallocMinVersion(llvm::Triple::OSType OS) {
+  switch (OS) {
+  default:
+    break;
+  case llvm::Triple::Darwin:
+  case llvm::Triple::MacOSX: // Earliest supporting version is 10.12.
+    return llvm::VersionTuple(10U, 12U);
+  case llvm::Triple::IOS:
+  case llvm::Triple::TvOS: // Earliest supporting version is 10.0.0.
+    return llvm::VersionTuple(10U);
+  case llvm::Triple::WatchOS: // Earliest supporting version is 3.0.0.
+    return llvm::VersionTuple(3U);
+  }
+
+  llvm_unreachable("Unexpected OS");
+}
+
+bool Darwin::isSizedDeallocationUnavailable() const {
+  llvm::Triple::OSType OS;
+
+  if (isTargetMacCatalyst())
+    return TargetVersion < sizedDeallocMinVersion(llvm::Triple::MacOSX);
+  switch (TargetPlatform) {
+  case MacOS: // Earlier than 10.12.
+    OS = llvm::Triple::MacOSX;
+    break;
+  case IPhoneOS:
+    OS = llvm::Triple::IOS;
+    break;
+  case TvOS: // Earlier than 10.0.
+    OS = llvm::Triple::TvOS;
+    break;
+  case WatchOS: // Earlier than 3.0.
+    OS = llvm::Triple::WatchOS;
+    break;
+  case DriverKit:
+  case XROS:
+    // Always available.
+    return false;
+  }
+
+  return TargetVersion < sizedDeallocMinVersion(OS);
+}
+
+void Darwin::addClangTargetOptions(
+    const llvm::opt::ArgList &DriverArgs, llvm::opt::ArgStringList &CC1Args,
+    Action::OffloadKind DeviceOffloadKind) const {
   // Pass "-faligned-alloc-unavailable" only when the user hasn't manually
   // enabled or disabled aligned allocations.
   if (!DriverArgs.hasArgNoClaim(options::OPT_faligned_allocation,
                                 options::OPT_fno_aligned_allocation) &&
       isAlignedAllocationUnavailable())
     CC1Args.push_back("-faligned-alloc-unavailable");
 
+  // Pass "-fno-sized-deallocation" only when the user hasn't manually enabled
+  // or disabled sized deallocations.
+  if (!DriverArgs.hasArgNoClaim(options::OPT_fsized_deallocation,
+                                options::OPT_fno_sized_deallocation) &&
+      isSizedDeallocationUnavailable())
+    CC1Args.push_back("-fno-sized-deallocation");
+
   addClangCC1ASTargetOptions(DriverArgs, CC1Args);
 
   // Enable compatibility mode for NSItemProviderCompletionHandler in

clang/lib/Driver/ToolChains/Darwin.h

@@ -511,6 +511,10 @@ class LLVM_LIBRARY_VISIBILITY Darwin : public MachO {
   /// targeting.
   bool isAlignedAllocationUnavailable() const;
 
+  /// Return true if c++14 sized deallocation functions are not implemented in
+  /// the c++ standard library of the deployment target we are targeting.
+  bool isSizedDeallocationUnavailable() const;
+
   void addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
                              llvm::opt::ArgStringList &CC1Args,
                              Action::OffloadKind DeviceOffloadKind) const override;

clang/lib/Driver/ToolChains/ZOS.cpp

@@ -36,6 +36,12 @@ void ZOS::addClangTargetOptions(const ArgList &DriverArgs,
   if (!DriverArgs.hasArgNoClaim(options::OPT_faligned_allocation,
                                 options::OPT_fno_aligned_allocation))
     CC1Args.push_back("-faligned-alloc-unavailable");
+
+  // Pass "-fno-sized-deallocation" only when the user hasn't manually enabled
+  // or disabled sized deallocations.
+  if (!DriverArgs.hasArgNoClaim(options::OPT_fsized_deallocation,
+                                options::OPT_fno_sized_deallocation))
+    CC1Args.push_back("-fno-sized-deallocation");
 }
 
 void zos::Assembler::ConstructJob(Compilation &C, const JobAction &JA,

clang/test/AST/ast-dump-expr-json.cpp

@@ -2333,7 +2333,7 @@ void TestNonADLCall3() {
 // CHECK-NEXT:         "kind": "FunctionDecl",
 // CHECK-NEXT:         "name": "operator delete",
 // CHECK-NEXT:         "type": {
-// CHECK-NEXT:          "qualType": "void (void *) noexcept"
+// CHECK-NEXT:          "qualType": "void (void *, unsigned long) noexcept"
 // CHECK-NEXT:         }
 // CHECK-NEXT:        },
 // CHECK-NEXT:        "inner": [

clang/test/AST/ast-dump-expr.cpp

@@ -164,7 +164,7 @@ void UnaryExpressions(int *p) {
   // CHECK-NEXT: DeclRefExpr 0x{{[^ ]*}} <col:8> 'int *' lvalue ParmVar 0x{{[^ ]*}} 'p' 'int *'
 
   ::delete p;
-  // CHECK: CXXDeleteExpr 0x{{[^ ]*}} <line:[[@LINE-1]]:3, col:12> 'void' global Function 0x{{[^ ]*}} 'operator delete' 'void (void *) noexcept'
+  // CHECK: CXXDeleteExpr 0x{{[^ ]*}} <line:[[@LINE-1]]:3, col:12> 'void' global Function 0x{{[^ ]*}} 'operator delete' 'void (void *, unsigned long) noexcept'
   // CHECK-NEXT: ImplicitCastExpr
   // CHECK-NEXT: DeclRefExpr 0x{{[^ ]*}} <col:12> 'int *' lvalue ParmVar 0x{{[^ ]*}} 'p' 'int *'