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[PAC] Ignore noexcept on function type when computing discriminator of member function pointers #109056

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Jan 21, 2025
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[PAC] Ignore noexcept on function type when computing discriminator of member function pointers #109056

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28 changes: 28 additions & 0 deletions clang/lib/AST/ASTContext.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3503,6 +3503,34 @@ uint16_t ASTContext::getPointerAuthTypeDiscriminator(QualType T) {
encodeTypeForFunctionPointerAuth(*this, Out, T);
} else {
T = T.getUnqualifiedType();
// Calls to member function pointers don't need to worry about
// language interop or the laxness of the C type compatibility rules.
// We just mangle the member pointer type directly, which is
// implicitly much stricter about type matching. However, we do
// strip any top-level exception specification before this mangling.
// C++23 requires calls to work when the function type is convertible
// to the pointer type by a function pointer conversion, which can
// change the exception specification. This does not technically
// require the exception specification to not affect representation,
// because the function pointer conversion is still always a direct
// value conversion and therefore an opportunity to resign the
// pointer. (This is in contrast to e.g. qualification conversions,
// which can be applied in nested pointer positions, effectively
// requiring qualified and unqualified representations to match.)
// However, it is pragmatic to ignore exception specifications
// because it allows a certain amount of `noexcept` mismatching
// to not become a visible ODR problem. This also leaves some
// room for the committee to add laxness to function pointer
// conversions in future standards.
if (auto *MPT = T->getAs<MemberPointerType>())
if (MPT->isMemberFunctionPointer()) {
QualType PointeeType = MPT->getPointeeType();
if (PointeeType->castAs<FunctionProtoType>()->getExceptionSpecType() !=
EST_None) {
QualType FT = getFunctionTypeWithExceptionSpec(PointeeType, EST_None);
T = getMemberPointerType(FT, MPT->getClass());
}
}
std::unique_ptr<MangleContext> MC(createMangleContext());
MC->mangleCanonicalTypeName(T, Out);
}
Expand Down
63 changes: 63 additions & 0 deletions clang/test/CodeGenCXX/ptrauth-member-function-pointer.cpp
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Original file line number Diff line number Diff line change
@@ -1,10 +1,12 @@
// 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
// 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
// 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
// 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
// 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
// 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

// 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
// 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
// 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
// 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
// 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
Expand All @@ -20,6 +22,10 @@
// 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
// 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

// CHECK: @_ZN22testNoexceptConversion6mfptr1E = global { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S19nonvirtual_noexceptEv, i32 0, i64 [[TYPEDISC3:.*]]) to i64), i64 0 },
// CHECK: @_ZN22testNoexceptConversion6mfptr2E = global { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S16virtual_noexceptEv_vfpthunk_, i32 0, i64 [[TYPEDISC3]]) to i64), i64 0 },
// CHECK: @_ZN22testNoexceptConversion15mfptr3_noexceptE = global { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S19nonvirtual_noexceptEv, i32 0, i64 [[TYPEDISC3]]) to i64), i64 0 },

// CHECK: @_ZTV5Base0 = unnamed_addr constant { [5 x ptr] } { [5 x ptr] [ptr null, ptr @_ZTI5Base0,
// CHECK-SAME: ptr ptrauth (ptr @_ZN5Base08virtual1Ev, i32 0, i64 55600, ptr getelementptr inbounds ({ [5 x ptr] }, ptr @_ZTV5Base0, i32 0, i32 0, i32 2)),
// CHECK-SAME: ptr ptrauth (ptr @_ZN5Base08virtual3Ev, i32 0, i64 53007, ptr getelementptr inbounds ({ [5 x ptr] }, ptr @_ZTV5Base0, i32 0, i32 0, i32 3)),
Expand Down Expand Up @@ -77,6 +83,9 @@ struct Derived1 : Base0, Base1 {
};

typedef void (Base0::*MethodTy0)();
#if __cplusplus >= 201703L
typedef void (Base0::*NoExceptMethodTy0)() noexcept;
#endif
typedef void (Base0::*VariadicMethodTy0)(int, ...);
typedef void (Derived0::*MethodTy1)();

Expand Down Expand Up @@ -293,6 +302,16 @@ void test1(Base0 *a0, MethodTy0 a1) {
(a0->*a1)();
}

// CXX17: define{{.*}} void @_Z14test1_noexceptP5Base0MS_DoFvvE(
// CXX17: %[[V14:.*]] = phi ptr [ %{{.*}}, {{.*}} ], [ %{{.*}}, {{.*}} ]
// CXX17: %[[V15:.*]] = phi i64 [ 0, {{.*}} ], [ [[TYPEDISC0]], {{.*}} ]
// CXX17: call void %[[V14]](ptr noundef nonnull align {{[0-9]+}} dereferenceable(8) %{{.*}}) {{.*}}[ "ptrauth"(i32 0, i64 %[[V15]]) ]
#if __cplusplus >= 201703L
void test1_noexcept(Base0 *a0, NoExceptMethodTy0 a1) {
(a0->*a1)();
}
#endif

// CHECK: define{{.*}} void @_Z15testConversion0M5Base0FvvEM8Derived0FvvE([2 x i64] %[[METHOD0_COERCE:.*]], [2 x i64] %[[METHOD1_COERCE:.*]])
// CHECK: %[[METHOD0:.*]] = alloca { i64, i64 }, align 8
// CHECK: %[[METHOD1:.*]] = alloca { i64, i64 }, align 8
Expand Down Expand Up @@ -438,3 +457,47 @@ void testArrayInit() {
void testConvertNull() {
VariadicMethodTy0 t = (VariadicMethodTy0)(MethodTy0{});
}

namespace testNoexceptConversion {

// CHECK-LABEL: define internal void @__cxx_global_var_init()
// CHECK: %[[V0:.*]] = load { i64, i64 }, ptr @_ZN22testNoexceptConversion15mfptr0_noexceptE, align 8
// CHECK: store { i64, i64 } %[[V0]], ptr @_ZN22testNoexceptConversion6mfptr4E, align 8

// CHECK: define {{.*}}void @_ZN22testNoexceptConversion5test0Ev()
// CHECK: %[[P0:.*]] = alloca { i64, i64 }, align 8
// CHECK: store { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S19nonvirtual_noexceptEv, i32 0, i64 [[TYPEDISC3]]) to i64), i64 0 }, ptr %[[P0]], align 8,

// CHECK: define {{.*}}void @_ZN22testNoexceptConversion5test1Ev()
// CHECK: %[[P0:.*]] = alloca { i64, i64 }, align 8
// CHECK: store { i64, i64 } { i64 ptrtoint (ptr ptrauth (ptr @_ZN22testNoexceptConversion1S16virtual_noexceptEv_vfpthunk_, i32 0, i64 [[TYPEDISC3]]) to i64), i64 0 }, ptr %[[P0]], align 8,

// CHECK: define {{.*}}void @_ZN22testNoexceptConversion5test2Ev()
// CHECK: %[[P0:.*]] = alloca { i64, i64 }, align 8
// CHECK: %[[V0:.*]] = load { i64, i64 }, ptr @_ZN22testNoexceptConversion15mfptr0_noexceptE, align 8
// CHECK: store { i64, i64 } %[[V0]], ptr %[[P0]], align 8,

struct S {
void nonvirtual_noexcept() noexcept;
virtual void virtual_noexcept() noexcept;
};

void (S::*mfptr0_noexcept)() noexcept;
void (S::*mfptr1)() = &S::nonvirtual_noexcept;
void (S::*mfptr2)() = &S::virtual_noexcept;
void (S::*mfptr3_noexcept)() noexcept = &S::nonvirtual_noexcept;
void (S::*mfptr4)() = mfptr0_noexcept;

void test0() {
void (S::*p0)() = &S::nonvirtual_noexcept;
}

void test1() {
void (S::*p0)() = &S::virtual_noexcept;
}

void test2() {
void (S::*p0)() = mfptr0_noexcept;
}

}
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