[clang] Patch for 6037

[Nathan Sidwell]

On 12/16/14 23:26, Richard Smith wrote:
> On Fri, Dec 12, 2014 at 6:53 AM, Nathan Sidwell <nathan at acm.org
> <mailto:nathan at acm.org>> wrote:

This patch addresses bug 6037 http://llvm.org/bugs/show_bug.cgi?id=6037
A request for a class definition to warn about inaccessible direct base classes.

> That said, you should be able to do this even more efficiently by collecting a
> list of all indirect base classes then checking if any direct base class is on
> the list. (If any is, you'll still need the code you already have, in order to
> describe the ambiguity.)

Patch adjusted.  Builds a std::set of indirect bases of the new class -- if it 
has more than 1 direct base.  Then checks if a direct base is in the set before 
determining the ambiguity of that base.[*]   Note that a direct and indirect 
base duplicate could exist, but not be ambiguous iff they are both virtual. 
Rather than track that data in the std::set, we just check the result of 
determining the base path ambiguity in the later loop.


> def warn_inaccessible_base_class : Warning<
>    "direct base %0 is inaccessible due to ambiguity:%1">,
>    InGroup<DiagGroup<"warning-flag">>;

Done.  Added -W[no-]inaccessible-base

A bunch of existing tests trigger.  For some of them I added 
-Wno-inaccessible-base to the test flags, for some I added the expected warning 
check -- depending on whether I judged the warning appropriate for the test 
case, or merely coincidental.  A new test 
tools/clang/test/SemaCXX/accessible-base.cpp is added

built and tested on x86-linux.

ok?

nathan

[*] As an aside, I wonder if completing the std:set with the direct bases and 
keeping it with the RecordDecl would speed up base conversion checks -- the base 
conversion machinery could use it for a quick 'is this even worth figuring out' 
check.
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