Is it needed to parse system headers? In general, we implement things like
this if they're needed for system headers but don't otherwise.
On Wed, Apr 27, 2016 at 6:19 AM, Dmitry Polukhin via cfe-commits <
cfe-commits@lists.llvm.org> wrote:
> I added example with 'B*' to 'A*' just to make sure that my patch doesn't
> break it accidentally in MSVC mode.
>
> As for 'A*' to 'B*" case, indeed it is not very common and it looks like
> someone just forgot to specify 'public'. I tried to find more real world
> examples in public source codes but without Google Code Search it is hard
> to do (GitHub doesn't support regexp search). Please let me know if you
> think it doesn't make sense to support this "feature" in Clang and I'll
> revert my patch.
>
> On Wed, Apr 27, 2016 at 5:12 AM, Richard Smith via cfe-commits <
> cfe-commits@lists.llvm.org> wrote:
>
>> On Tue, Apr 26, 2016 at 7:04 PM, David Majnemer via cfe-commits <
>> cfe-commits@lists.llvm.org> wrote:
>>
>>> Visual Studio 2015 (19.00.23720.0) reports:
>>>
>>> error C2243: 'static_cast': conversion from 'B *' to 'A *' exists, but
>>> is inaccessible
>>>
>>
>> Right, it's the other direction ('A *' to 'B *') that this patch is
>> permitting.
>>
>>
>>> On Tue, Apr 26, 2016 at 6:33 PM, Richard Smith via cfe-commits <
>>> cfe-commits@lists.llvm.org> wrote:
>>>
>>>> As noted in PR27337, this only occurs in one WTL sample, and we have no
>>>> evidence that it actually occurs in real code. Have you seen uses of this
>>>> in the wild? We generally don't want to add compatibility for MSVC bugs
>>>> unless there's some real-world motivation.
>>>>
>>>>
>>>> On Tue, Apr 26, 2016 at 2:21 AM, Dmitry Polukhin via cfe-commits <
>>>> cfe-commits@lists.llvm.org> wrote:
>>>>
>>>>> Author: dpolukhin
>>>>> Date: Tue Apr 26 04:21:17 2016
>>>>> New Revision: 267534
>>>>>
>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=267534&view=rev
>>>>> Log:
>>>>> [MSVC] PR27337: allow static_cast from private base to derived for WTL
>>>>>
>>>>> MSVC doesn't report even warning for cast from private base class to
>>>>> derived.
>>>>>
>>>>> Differential Revision: http://reviews.llvm.org/D19477
>>>>>
>>>>> Added:
>>>>> cfe/trunk/test/SemaCXX/ext_ms_downcast.cpp (with props)
>>>>> Modified:
>>>>> cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>>> cfe/trunk/lib/Sema/SemaCast.cpp
>>>>>
>>>>> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=267534&r1=267533&r2=267534&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>>>>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Apr 26
>>>>> 04:21:17 2016
>>>>> @@ -5764,6 +5764,9 @@ def err_static_downcast_via_virtual : Er
>>>>> "cannot cast %0 to %1 via virtual base %2">;
>>>>> def err_downcast_from_inaccessible_base : Error<
>>>>> "cannot cast %select{private|protected}2 base class %1 to %0">;
>>>>> +def ext_ms_downcast_from_inaccessible_base : ExtWarn<
>>>>> + "casting from %select{private|protected}2 base class %1 to derived
>>>>> class %0 is a Microsoft extension">,
>>>>> + InGroup<MicrosoftCast>;
>>>>> def err_upcast_to_inaccessible_base : Error<
>>>>> "cannot cast %0 to its %select{private|protected}2 base class %1">;
>>>>> def err_bad_dynamic_cast_not_ref_or_ptr : Error<
>>>>>
>>>>> Modified: cfe/trunk/lib/Sema/SemaCast.cpp
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaCast.cpp?rev=267534&r1=267533&r2=267534&view=diff
>>>>>
>>>>> ==============================================================================
>>>>> --- cfe/trunk/lib/Sema/SemaCast.cpp (original)
>>>>> +++ cfe/trunk/lib/Sema/SemaCast.cpp Tue Apr 26 04:21:17 2016
>>>>> @@ -1344,10 +1344,11 @@ TryStaticDowncast(Sema &Self, CanQualTyp
>>>>> }
>>>>>
>>>>> if (!CStyle) {
>>>>> - switch (Self.CheckBaseClassAccess(OpRange.getBegin(),
>>>>> - SrcType, DestType,
>>>>> - Paths.front(),
>>>>> -
>>>>> diag::err_downcast_from_inaccessible_base)) {
>>>>> + unsigned Diag = Self.getLangOpts().MSVCCompat
>>>>> + ? diag::ext_ms_downcast_from_inaccessible_base
>>>>> + : diag::err_downcast_from_inaccessible_base;
>>>>> + switch (Self.CheckBaseClassAccess(OpRange.getBegin(), SrcType,
>>>>> DestType,
>>>>> + Paths.front(), Diag)) {
>>>>> case Sema::AR_accessible:
>>>>> case Sema::AR_delayed: // be optimistic
>>>>> case Sema::AR_dependent: // be optimistic
>>>>>
>>>>> Added: cfe/trunk/test/SemaCXX/ext_ms_downcast.cpp
>>>>> URL:
>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/ext_ms_downcast.cpp?rev=267534&view=auto
>>>>>
>>>>> ==============================================================================
>>>>> --- cfe/trunk/test/SemaCXX/ext_ms_downcast.cpp (added)
>>>>> +++ cfe/trunk/test/SemaCXX/ext_ms_downcast.cpp Tue Apr 26 04:21:17 2016
>>>>> @@ -0,0 +1,40 @@
>>>>> +// RUN: %clang_cc1 -fsyntax-only -fms-compatibility -verify %s
>>>>> +// RUN: %clang_cc1 -fsyntax-only -DNO_MS_COMPATIBILITY -verify %s
>>>>> +
>>>>> +// Minimal reproducer.
>>>>> +class A {};
>>>>> +class B : A {}; // expected-note 2 {{implicitly declared private
>>>>> here}}
>>>>> +
>>>>> +B* foo(A* p) {
>>>>> + return static_cast<B*>(p);
>>>>> +#ifdef NO_MS_COMPATIBILITY
>>>>> + // expected-error@-2 {{cannot cast private base class 'A' to 'B'}}
>>>>> +#else
>>>>> + // expected-warning@-4 {{casting from private base class 'A' to
>>>>> derived class 'B' is a Microsoft extension}}
>>>>> +#endif
>>>>> +}
>>>>> +
>>>>> +A* bar(B* p) {
>>>>> + return static_cast<A*>(p); // expected-error {{cannot cast 'B' to
>>>>> its private base class 'A'}}
>>>>> +}
>>>>> +
>>>>> +// from atlframe.h
>>>>> +template <class T>
>>>>> +class CUpdateUI {
>>>>> +public:
>>>>> + CUpdateUI() {
>>>>> + T* pT = static_cast<T*>(this);
>>>>> +#ifdef NO_MS_COMPATIBILITY
>>>>> + // expected-error@-2 {{cannot cast private base class}}
>>>>> +#else
>>>>> + // expected-warning@-4 {{casting from private base class
>>>>> 'CUpdateUI<CMDIFrame>' to derived class 'CMDIFrame' is a Microsoft
>>>>> extension}}
>>>>> +#endif
>>>>> + }
>>>>> +};
>>>>> +
>>>>> +// from sample WTL/MDIDocVw (mainfrm.h
>>>>> +class CMDIFrame : CUpdateUI<CMDIFrame> {};
>>>>> +// expected-note@-1 {{implicitly declared private here}}
>>>>> +// expected-note@-2 {{in instantiation of member function}}
>>>>> +
>>>>> +CMDIFrame wndMain;
>>>>>
>>>>> Propchange: cfe/trunk/test/SemaCXX/ext_ms_downcast.cpp
>>>>>
>>>>> ------------------------------------------------------------------------------
>>>>> svn:eol-style = native
>>>>>
>>>>> Propchange: cfe/trunk/test/SemaCXX/ext_ms_downcast.cpp
>>>>>
>>>>> ------------------------------------------------------------------------------
>>>>> svn:keywords = "Author Date Id Rev URL"
>>>>>
>>>>> Propchange: cfe/trunk/test/SemaCXX/ext_ms_downcast.cpp
>>>>>
>>>>> ------------------------------------------------------------------------------
>>>>> svn:mime-type = text/plain
>>>>>
>>>>>
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>>>>> cfe-commits@lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>>>>
>>>>
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