<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Thu, Apr 25, 2013 at 1:01 AM, Handa, Ramneek <span dir="ltr"><<a href="mailto:Ramneek.Handa@sc.com" target="_blank">Ramneek.Handa@sc.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I am confused on how to find this in the std document.<br>
What I find in there is (from n3485):<br>
1. Page-231, clause 4 - Access control is applied uniformly to all<br>
names, whether the names are referred to from declarations or<br>
expressions.<br>
2. Page-231, clause 5 - It should be noted that it is access to members<br>
and base classes that is controlled, not their visibility. Names<br>
of members are still visible, and implicit conversions to base classes<br>
are still considered, when those members<br>
and base classes are inaccessible. The interpretation of a given<br>
construct is established without regard to<br>
access control. If the interpretation established makes use of<br>
inaccessible member names or base classes, the<br>
construct is ill-formed.<br>
<br>
I am not sure what they mean by visibility?<br>
<br>
Could you send me what sections and clauses are you referring to?<br></blockquote><div><br></div><div style>We're not a C++ support forum; your question might be better directed to stackoverflow. If you want to understand how the C++11 rules differ from C++03, you should compare the C++11 and C++03 standards. Search for things like "would be ill-formed" and "type deduction fails".</div>
<div style><br></div><div style>If you think that Clang is actually wrong here (if this code is still rejected with -std=c++11, for instance), please provide preprocessed (and preferably reduced) source code.</div><div> </div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Thanks for response again.<br>
<br>
Regards.<br>
<div><div class="h5"><br>
<br>
-----Original Message-----<br>
From: <a href="mailto:cfe-dev-bounces@cs.uiuc.edu">cfe-dev-bounces@cs.uiuc.edu</a> [mailto:<a href="mailto:cfe-dev-bounces@cs.uiuc.edu">cfe-dev-bounces@cs.uiuc.edu</a>]<br>
On Behalf Of John McCall<br>
Sent: Thursday, April 25, 2013 2:27 PM<br>
To: Ramneek Handa<br>
Cc: clang-dev Developers<br>
Subject: Re: [cfe-dev] private class members access fails with<br>
meta-programming in clang?<br>
<br>
On Apr 24, 2013, at 9:20 AM, Ramneek Handa <<a href="mailto:ramneekhanda@gmail.com">ramneekhanda@gmail.com</a>><br>
wrote:<br>
> I thought this should pass with clang.<br>
><br>
> x-- start --x<br>
><br>
> #include <boost/mpl/has_xxx.hpp><br>
><br>
> BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(hasSomething, Data, false);<br>
><br>
> class A {<br>
> private:<br>
> struct Data {<br>
> };<br>
> };<br>
><br>
><br>
> void function(bool val = hasSomething<A>::value) {}<br>
><br>
><br>
> x-- end --x<br>
><br>
> however it produces following output:<br>
> test_private_data.cpp:3:49: error: 'Data' is a private member of 'A'<br>
> BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(hasSomething, Data, false);<br>
> ^<br>
> /usr/include/boost/mpl/has_xxx.hpp:195:68: note: expanded from macro<br>
'BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF'<br>
> , boost::mpl::aux::type_wrapper<BOOST_MSVC_TYPENAME U::name>* = 0 \<br>
> ^<br>
> test_private_data.cpp:3:1: note: while substituting deduced template<br>
arguments into function template 'test' [with U = A]<br>
> BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(hasSomething, Data, false);<br>
> ^<br>
> /usr/include/boost/mpl/has_xxx.hpp:193:41: note: expanded from macro<br>
'BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF'<br>
> static boost::mpl::aux::yes_tag test( \<br>
> ^<br>
> test_private_data.cpp:12:26: note: in instantiation of template class<br>
'hasSomething<A, mpl_::bool_<false> >' requested here<br>
> void function(bool val = hasSomething<A>::value) {}<br>
> ^<br>
> 1 error generated.<br>
> /usr/bin/ld: /tmp/test_private_data-Hatffv.o: No such file: No such<br>
file or directory<br>
> clang: error: linker command failed with exit code 1 (use -v to see<br>
invocation)<br>
><br>
><br>
><br>
><br>
> BUT it passes with GCC.<br>
><br>
> Which one is right?<br>
<br>
I assume that Boost is using SFINAE here in its check. Access control<br>
violations were not subject to SFINAE prior to C++11, and Clang is<br>
correct<br>
to diagnose it. You can compile with -std=c++11 to make this work; the<br>
trait will return 'false'.<br>
<br>
John.<br>
<br>
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