[libcxx] r260337 - Fix overload sets of strchr, strpbrk, strrchr, memchr and strstr from

[Richard Smith via cfe-commits]

On Wed, Feb 10, 2016 at 10:32 AM, Tim Northover <t.p.northover at gmail.com> wrote:
> Hi Richard,
>
> On 9 February 2016 at 16:59, Richard Smith via cfe-commits
> <cfe-commits at lists.llvm.org> wrote:
>> Fix overload sets of strchr, strpbrk, strrchr, memchr and strstr from
>> <string.h> and wcschr, wcspbrk, wcsrchr, wmemchr, and wcsstr from <wchar.h> to
>> provide a const-correct overload set even when the underlying C library does
>> not.
>
> This seems to have caused breakage on one of compiler-rt's tests on
> Darwin: lib/asan/test/asan_str_test.cc if I'm reading the runes
> correctly. See http://lab.llvm.org:8080/green/job/clang-stage1-cmake-RA_check/10117/
> for example.
>
> I'm not quite sure what's going on, but it seems to involve enable_if
> disabling some overload checks, leading to an inconsistent set of
> possible functions. That's probably an independent bug in clang
> (there's certainly no mangling to support it in Itanium), but I
> suspect libc++ shouldn't be trying to produce such combinations
> anyway.
>
> The smallest test case with the essential Clang details I've found is:
>
> char *foo(const char *);
> char *foo(char *);
> __attribute__ ((__enable_if__(true, ""))) const char *foo(const char *);
>
> void test(char *(*)(const char *));
> void test(char *(*)(char *));
>
> void func(char *in) {
>   test(&foo);
> }
>
> Do you have any ideas on what to do, because I'm a bit stuck I'm
> afraid. I can give you preprocessed source if you're struggling to
> reproduce the issue (it's 2.4MB for the default 7ish for
> -frewrite-includes).

Thanks for the reduction. I've been trying to reproduce this, but
compiler-rt won't build for me (apparently something has broken in its
support for libc++ since I last used it -- it's passing -stdlib=libc++
to compile actions but not to the link).