Author: rnk
Date: Fri Oct 27 15:48:41 2017
New Revision: 316807
URL: http://llvm.org/viewvc/llvm-project?rev=316807&view=rev
Log:
[MS] Allow access to ambiguous, inaccessible direct bases
Summary:
Clang typically warns that in the following class hierarchy, 'A' is
inaccessible because there is no series of casts that the user can
write to access it unambiguously:
struct A { };
struct B : A { };
struct C : A, B { };
MSVC allows the user to convert from C* to A*, though, and we've
encountered this issue in the latest Windows SDK headers.
This patch allows this conversion when -fms-compatibility is set and
adds a warning for it under -Wmicrosoft-inaccessible-base.
Reviewers: rsmith
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D39389
Added:
cfe/trunk/test/CodeGenCXX/microsoft-inaccessible-base.cpp
Modified:
cfe/trunk/include/clang/Basic/DiagnosticGroups.td
cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
cfe/trunk/lib/Sema/SemaDeclCXX.cpp
cfe/trunk/test/SemaCXX/accessible-base.cpp
Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=316807&r1=316806&r2=316807&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Fri Oct 27 15:48:41 2017
@@ -890,6 +890,7 @@ def MicrosoftVoidPseudoDtor : DiagGroup<
def MicrosoftAnonTag : DiagGroup<"microsoft-anon-tag">;
def MicrosoftCommentPaste : DiagGroup<"microsoft-comment-paste">;
def MicrosoftEndOfFile : DiagGroup<"microsoft-end-of-file">;
+def MicrosoftInaccessibleBase : DiagGroup<"microsoft-inaccessible-base">;
// Aliases.
def : DiagGroup<"msvc-include", [MicrosoftInclude]>;
// -Wmsvc-include = -Wmicrosoft-include
Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=316807&r1=316806&r2=316807&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Fri Oct 27 15:48:41
2017
@@ -7565,6 +7565,9 @@ def err_ambiguous_derived_to_base_conv :
def err_ambiguous_memptr_conv : Error<
"ambiguous conversion from pointer to member of %select{base|derived}0 "
"class %1 to pointer to member of %select{derived|base}0 class %2:%3">;
+def ext_ms_ambiguous_direct_base : ExtWarn<
+ "accessing inaccessible direct base %0 of %1 is a Microsoft extension">,
+ InGroup<MicrosoftInaccessibleBase>;
def err_memptr_conv_via_virtual : Error<
"conversion from pointer to member of class %0 to pointer to member "
Modified: cfe/trunk/lib/Sema/SemaDeclCXX.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDeclCXX.cpp?rev=316807&r1=316806&r2=316807&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaDeclCXX.cpp (original)
+++ cfe/trunk/lib/Sema/SemaDeclCXX.cpp Fri Oct 27 15:48:41 2017
@@ -2503,13 +2503,8 @@ bool Sema::IsDerivedFrom(SourceLocation
return DerivedRD->isDerivedFrom(BaseRD, Paths);
}
-void Sema::BuildBasePathArray(const CXXBasePaths &Paths,
- CXXCastPath &BasePathArray) {
- assert(BasePathArray.empty() && "Base path array must be empty!");
- assert(Paths.isRecordingPaths() && "Must record paths!");
-
- const CXXBasePath &Path = Paths.front();
-
+static void BuildBasePathArray(const CXXBasePath &Path,
+ CXXCastPath &BasePathArray) {
// We first go backward and check if we have a virtual base.
// FIXME: It would be better if CXXBasePath had the base specifier for
// the nearest virtual base.
@@ -2526,6 +2521,13 @@ void Sema::BuildBasePathArray(const CXXB
BasePathArray.push_back(const_cast<CXXBaseSpecifier*>(Path[I].Base));
}
+
+void Sema::BuildBasePathArray(const CXXBasePaths &Paths,
+ CXXCastPath &BasePathArray) {
+ assert(BasePathArray.empty() && "Base path array must be empty!");
+ assert(Paths.isRecordingPaths() && "Must record paths!");
+ return ::BuildBasePathArray(Paths.front(), BasePathArray);
+}
/// CheckDerivedToBaseConversion - Check whether the Derived-to-Base
/// conversion (where Derived and Base are class types) is
/// well-formed, meaning that the conversion is unambiguous (and
@@ -2557,23 +2559,42 @@ Sema::CheckDerivedToBaseConversion(QualT
"Can only be used with a derived-to-base conversion");
(void)DerivationOkay;
- if (!Paths.isAmbiguous(Context.getCanonicalType(Base).getUnqualifiedType()))
{
+ const CXXBasePath *Path = nullptr;
+ if (!Paths.isAmbiguous(Context.getCanonicalType(Base).getUnqualifiedType()))
+ Path = &Paths.front();
+
+ // For MSVC compatibility, check if Derived directly inherits from Base.
Clang
+ // warns about this hierarchy under -Winaccessible-base, but MSVC allows the
+ // user to access such bases.
+ if (!Path && getLangOpts().MSVCCompat) {
+ for (const CXXBasePath &PossiblePath : Paths) {
+ if (PossiblePath.size() == 1) {
+ Path = &PossiblePath;
+ if (AmbigiousBaseConvID)
+ Diag(Loc, diag::ext_ms_ambiguous_direct_base)
+ << Base << Derived << Range;
+ break;
+ }
+ }
+ }
+
+ if (Path) {
if (!IgnoreAccess) {
// Check that the base class can be accessed.
- switch (CheckBaseClassAccess(Loc, Base, Derived, Paths.front(),
- InaccessibleBaseID)) {
- case AR_inaccessible:
- return true;
- case AR_accessible:
- case AR_dependent:
- case AR_delayed:
- break;
+ switch (
+ CheckBaseClassAccess(Loc, Base, Derived, *Path, InaccessibleBaseID))
{
+ case AR_inaccessible:
+ return true;
+ case AR_accessible:
+ case AR_dependent:
+ case AR_delayed:
+ break;
}
}
// Build a base path if necessary.
if (BasePath)
- BuildBasePathArray(Paths, *BasePath);
+ ::BuildBasePathArray(*Path, *BasePath);
return false;
}
Added: cfe/trunk/test/CodeGenCXX/microsoft-inaccessible-base.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/microsoft-inaccessible-base.cpp?rev=316807&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/microsoft-inaccessible-base.cpp (added)
+++ cfe/trunk/test/CodeGenCXX/microsoft-inaccessible-base.cpp Fri Oct 27
15:48:41 2017
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -fms-compatibility -triple x86_64-windows-msvc %s
-emit-llvm -o - | FileCheck %s
+
+// Make sure we choose the *direct* base path when doing these conversions.
+
+// CHECK: %struct.C = type { %struct.A, %struct.B }
+// CHECK: %struct.D = type { %struct.B, %struct.A }
+
+struct A { int a; };
+struct B : A { int b; };
+
+struct C : A, B { };
+extern "C" A *a_from_c(C *p) { return p; }
+// CHECK-LABEL: define %struct.A* @a_from_c(%struct.C* %{{.*}})
+// CHECK: bitcast %struct.C* %{{.*}} to %struct.A*
+
+struct D : B, A { };
+extern "C" A *a_from_d(D *p) { return p; }
+// CHECK-LABEL: define %struct.A* @a_from_d(%struct.D* %{{.*}})
+// CHECK: %[[p_i8:[^ ]*]] = bitcast %struct.D* %{{.*}} to i8*
+// CHECK: getelementptr inbounds i8, i8* %[[p_i8]], i64 8
Modified: cfe/trunk/test/SemaCXX/accessible-base.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/accessible-base.cpp?rev=316807&r1=316806&r2=316807&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/accessible-base.cpp (original)
+++ cfe/trunk/test/SemaCXX/accessible-base.cpp Fri Oct 27 15:48:41 2017
@@ -1,10 +1,11 @@
// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -DMS -fms-compatibility -Wmicrosoft-inaccessible-base
-fsyntax-only -verify %s
struct A {
int a;
};
-struct X1 : virtual A
+struct X1 : virtual A
{};
struct Y1 : X1, virtual A
@@ -13,7 +14,7 @@ struct Y1 : X1, virtual A
struct Y2 : X1, A // expected-warning{{direct base 'A' is inaccessible due to
ambiguity:\n struct Y2 -> struct X1 -> struct A\n struct Y2 -> struct A}}
{};
-struct X2 : A
+struct X2 : A
{};
struct Z1 : X2, virtual A // expected-warning{{direct base 'A' is inaccessible
due to ambiguity:\n struct Z1 -> struct X2 -> struct A\n struct Z1 ->
struct A}}
@@ -21,3 +22,30 @@ struct Z1 : X2, virtual A // expected-wa
struct Z2 : X2, A // expected-warning{{direct base 'A' is inaccessible due to
ambiguity:\n struct Z2 -> struct X2 -> struct A\n struct Z2 -> struct A}}
{};
+
+A *y2_to_a(Y2 *p) {
+#ifdef MS
+ // expected-warning@+4 {{accessing inaccessible direct base 'A' of 'Y2' is a
Microsoft extension}}
+#else
+ // expected-error@+2 {{ambiguous conversion}}
+#endif
+ return p;
+}
+
+A *z1_to_a(Z1 *p) {
+#ifdef MS
+ // expected-warning@+4 {{accessing inaccessible direct base 'A' of 'Z1' is a
Microsoft extension}}
+#else
+ // expected-error@+2 {{ambiguous conversion}}
+#endif
+ return p;
+}
+
+A *z1_to_a(Z2 *p) {
+#ifdef MS
+ // expected-warning@+4 {{accessing inaccessible direct base 'A' of 'Z2' is a
Microsoft extension}}
+#else
+ // expected-error@+2 {{ambiguous conversion}}
+#endif
+ return p;
+}
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