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[PAC] Ignore noexcept on function type when computing discriminator of member function pointers (llvm#109056)
This fixes a bug where a member function pointer signed using a function type with noexcept as the discriminator was being authenticated using a function type without noexcept. Fixes llvm#106487.
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‎clang/lib/AST/ASTContext.cpp

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@@ -3503,6 +3503,34 @@ uint16_t ASTContext::getPointerAuthTypeDiscriminator(QualType T) {
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encodeTypeForFunctionPointerAuth(*this, Out, T);
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} else {
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T = T.getUnqualifiedType();
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// Calls to member function pointers don't need to worry about
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// language interop or the laxness of the C type compatibility rules.
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// We just mangle the member pointer type directly, which is
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// implicitly much stricter about type matching. However, we do
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// strip any top-level exception specification before this mangling.
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// C++23 requires calls to work when the function type is convertible
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// to the pointer type by a function pointer conversion, which can
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// change the exception specification. This does not technically
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// require the exception specification to not affect representation,
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// because the function pointer conversion is still always a direct
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// value conversion and therefore an opportunity to resign the
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// pointer. (This is in contrast to e.g. qualification conversions,
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// which can be applied in nested pointer positions, effectively
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// requiring qualified and unqualified representations to match.)
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// However, it is pragmatic to ignore exception specifications
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// because it allows a certain amount of `noexcept` mismatching
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// to not become a visible ODR problem. This also leaves some
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// room for the committee to add laxness to function pointer
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// conversions in future standards.
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if (auto *MPT = T->getAs<MemberPointerType>())
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if (MPT->isMemberFunctionPointer()) {
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QualType PointeeType = MPT->getPointeeType();
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if (PointeeType->castAs<FunctionProtoType>()->getExceptionSpecType() !=
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EST_None) {
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QualType FT = getFunctionTypeWithExceptionSpec(PointeeType, EST_None);
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T = getMemberPointerType(FT, MPT->getClass());
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}
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}
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std::unique_ptr<MangleContext> MC(createMangleContext());
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MC->mangleCanonicalTypeName(T, Out);
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}

‎clang/test/CodeGenCXX/ptrauth-member-function-pointer.cpp

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@@ -1,10 +1,12 @@
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// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -o - %s | FileCheck -check-prefixes=CHECK,NODEBUG,DARWIN %s
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// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++17 -O1 -disable-llvm-passes -o - %s | FileCheck -check-prefixes=CHECK,NODEBUG,DARWIN,CXX17 %s
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// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -debug-info-kind=limited -o - %s | FileCheck -check-prefixes=CHECK,DARWIN %s
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// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -stack-protector 1 -o - %s | FileCheck %s -check-prefix=STACK-PROT
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// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -stack-protector 2 -o - %s | FileCheck %s -check-prefix=STACK-PROT
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// RUN: %clang_cc1 -triple arm64-apple-ios -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -stack-protector 3 -o - %s | FileCheck %s -check-prefix=STACK-PROT
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// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -o - %s | FileCheck -check-prefixes=CHECK,NODEBUG,ELF %s
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// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++17 -O1 -disable-llvm-passes -o - %s | FileCheck -check-prefixes=CHECK,NODEBUG,ELF,CXX17 %s
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// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -debug-info-kind=limited -o - %s | FileCheck -check-prefixes=CHECK,ELF %s
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// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -stack-protector 1 -o - %s | FileCheck %s -check-prefix=STACK-PROT
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// RUN: %clang_cc1 -triple aarch64-linux-gnu -fptrauth-calls -fptrauth-intrinsics -emit-llvm -std=c++11 -O1 -disable-llvm-passes -stack-protector 2 -o - %s | FileCheck %s -check-prefix=STACK-PROT
@@ -20,6 +22,10 @@
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// CHECK: @__const._Z13testArrayInitv.c0 = private unnamed_addr constant %struct.Class0 { { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN5Base011nonvirtual0Ev, i32 0, i64 35591) to i64), i64 0 } }, align 8
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// CHECK: @__const._Z13testArrayInitv.c1 = private unnamed_addr constant %struct.Class0 { { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN5Base08virtual1Ev_vfpthunk_, i32 0, i64 35591) to i64), i64 0 } }, align 8
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// CHECK: @_ZN22testNoexceptConversion6mfptr1E = global { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S19nonvirtual_noexceptEv, i32 0, i64 [[TYPEDISC3:.*]]) to i64), i64 0 },
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// CHECK: @_ZN22testNoexceptConversion6mfptr2E = global { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S16virtual_noexceptEv_vfpthunk_, i32 0, i64 [[TYPEDISC3]]) to i64), i64 0 },
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// CHECK: @_ZN22testNoexceptConversion15mfptr3_noexceptE = global { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S19nonvirtual_noexceptEv, i32 0, i64 [[TYPEDISC3]]) to i64), i64 0 },
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// CHECK: @_ZTV5Base0 = unnamed_addr constant { [5 x ptr] } { [5 x ptr] [ptr null, ptr @_ZTI5Base0,
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// CHECK-SAME: ptr ptrauth (ptr @_ZN5Base08virtual1Ev, i32 0, i64 55600, ptr getelementptr inbounds ({ [5 x ptr] }, ptr @_ZTV5Base0, i32 0, i32 0, i32 2)),
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// CHECK-SAME: ptr ptrauth (ptr @_ZN5Base08virtual3Ev, i32 0, i64 53007, ptr getelementptr inbounds ({ [5 x ptr] }, ptr @_ZTV5Base0, i32 0, i32 0, i32 3)),
@@ -77,6 +83,9 @@ struct Derived1 : Base0, Base1 {
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};
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typedef void (Base0::*MethodTy0)();
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#if __cplusplus >= 201703L
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typedef void (Base0::*NoExceptMethodTy0)() noexcept;
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#endif
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typedef void (Base0::*VariadicMethodTy0)(int, ...);
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typedef void (Derived0::*MethodTy1)();
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@@ -293,6 +302,16 @@ void test1(Base0 *a0, MethodTy0 a1) {
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(a0->*a1)();
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}
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// CXX17: define{{.*}} void @_Z14test1_noexceptP5Base0MS_DoFvvE(
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// CXX17: %[[V14:.*]] = phi ptr [ %{{.*}}, {{.*}} ], [ %{{.*}}, {{.*}} ]
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// CXX17: %[[V15:.*]] = phi i64 [ 0, {{.*}} ], [ [[TYPEDISC0]], {{.*}} ]
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// CXX17: call void %[[V14]](ptr noundef nonnull align {{[0-9]+}} dereferenceable(8) %{{.*}}) {{.*}}[ "ptrauth"(i32 0, i64 %[[V15]]) ]
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#if __cplusplus >= 201703L
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void test1_noexcept(Base0 *a0, NoExceptMethodTy0 a1) {
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(a0->*a1)();
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}
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#endif
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// CHECK: define{{.*}} void @_Z15testConversion0M5Base0FvvEM8Derived0FvvE([2 x i64] %[[METHOD0_COERCE:.*]], [2 x i64] %[[METHOD1_COERCE:.*]])
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// CHECK: %[[METHOD0:.*]] = alloca { i64, i64 }, align 8
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// CHECK: %[[METHOD1:.*]] = alloca { i64, i64 }, align 8
@@ -438,3 +457,47 @@ void testArrayInit() {
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void testConvertNull() {
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VariadicMethodTy0 t = (VariadicMethodTy0)(MethodTy0{});
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}
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namespace testNoexceptConversion {
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// CHECK-LABEL: define internal void @__cxx_global_var_init()
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// CHECK: %[[V0:.*]] = load { i64, i64 }, ptr @_ZN22testNoexceptConversion15mfptr0_noexceptE, align 8
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// CHECK: store { i64, i64 } %[[V0]], ptr @_ZN22testNoexceptConversion6mfptr4E, align 8
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// CHECK: define {{.*}}void @_ZN22testNoexceptConversion5test0Ev()
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// CHECK: %[[P0:.*]] = alloca { i64, i64 }, align 8
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// CHECK: store { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S19nonvirtual_noexceptEv, i32 0, i64 [[TYPEDISC3]]) to i64), i64 0 }, ptr %[[P0]], align 8,
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// CHECK: define {{.*}}void @_ZN22testNoexceptConversion5test1Ev()
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// CHECK: %[[P0:.*]] = alloca { i64, i64 }, align 8
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// CHECK: store { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S16virtual_noexceptEv_vfpthunk_, i32 0, i64 [[TYPEDISC3]]) to i64), i64 0 }, ptr %[[P0]], align 8,
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// CHECK: define {{.*}}void @_ZN22testNoexceptConversion5test2Ev()
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// CHECK: %[[P0:.*]] = alloca { i64, i64 }, align 8
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// CHECK: %[[V0:.*]] = load { i64, i64 }, ptr @_ZN22testNoexceptConversion15mfptr0_noexceptE, align 8
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// CHECK: store { i64, i64 } %[[V0]], ptr %[[P0]], align 8,
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struct S {
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void nonvirtual_noexcept() noexcept;
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virtual void virtual_noexcept() noexcept;
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};
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void (S::*mfptr0_noexcept)() noexcept;
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void (S::*mfptr1)() = &S::nonvirtual_noexcept;
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void (S::*mfptr2)() = &S::virtual_noexcept;
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void (S::*mfptr3_noexcept)() noexcept = &S::nonvirtual_noexcept;
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void (S::*mfptr4)() = mfptr0_noexcept;
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void test0() {
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void (S::*p0)() = &S::nonvirtual_noexcept;
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}
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void test1() {
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void (S::*p0)() = &S::virtual_noexcept;
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}
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void test2() {
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void (S::*p0)() = mfptr0_noexcept;
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}
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}

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