r193934 - Default to use libc++ on OS X 10.9+ and iOS 7+.

[Bob Wilson]

Would you like to contribute a patch to clarify that documentation?  I’m not sure what you’re asking for here.

On Feb 4, 2014, at 12:20 PM, Timur Iskhodzhanov <timurrrr at google.com> wrote:

> ping?
> 
> I've spent a fair amount of time debugging this yesterday.
> 
> 2013-11-05 Nico Weber <thakis at chromium.org>:
>> On Tue, Nov 5, 2013 at 9:44 AM, Bob Wilson <bob.wilson at apple.com> wrote:
>>> 
>>> On OS X the libc++ headers are meant to be installed along with clang.  If
>>> you check out the libc++ sources in the LLVM projects directory, they should
>>> be installed in the right place.
>> 
>> 
>> Thanks, that makes sense. Should http://clang.llvm.org/get_started.html
>> mention checking out libc++, since it sounds that's now a requirement on OS
>> X?
>> 
>>> 
>>> 
>>> On Nov 5, 2013, at 9:42 AM, Howard Hinnant <hhinnant at apple.com> wrote:
>>> 
>>>> When I use tot clang, (and want libc++), I will forbid clang from
>>>> looking the std::headers, and then tell it exactly where the headers are,
>>>> e.g.:
>>>> 
>>>> $ clang++ -stdlib=libc++ -std=c++11 -nostdinc++ -I../libcxx/include
>>>> test.cpp
>>>> 
>>>> Howard
>>>> 
>>>> On Nov 5, 2013, at 12:35 PM, Nico Weber <thakis at chromium.org> wrote:
>>>> 
>>>>> In addition to the performance issues, libc++ apparently can't be found
>>>>> by clang: http://llvm.org/bugs/show_bug.cgi?id=17821
>>>>> 
>>>>> 
>>>>> On Sat, Nov 2, 2013 at 10:35 PM, Bob Wilson <bob.wilson at apple.com>
>>>>> wrote:
>>>>> I’m not familiar with those performance issues, so I’m CC’ing Howard in
>>>>> case he can provide any details on those issues.  In general, we’re in the
>>>>> process of migrating away from libstdc++ on OS X and iOS, so we really do
>>>>> want the default to be libc++ regardless of the language mode.  If you have
>>>>> particularly performance sensitive code, you can always choose to use
>>>>> libstdc++.
>>>>> 
>>>>> On Nov 2, 2013, at 7:05 PM, Nico Weber <thakis at chromium.org> wrote:
>>>>> 
>>>>>> Thanks for upstreaming this!
>>>>>> 
>>>>>> Should this only happen in C++11 mode? libc++ seems to be measurably
>>>>>> slower than libstdc++ in C++03 mode (PR17703, PR14554, PR14555).
>>>>>> 
>>>>>> 
>>>>>> On Sat, Nov 2, 2013 at 4:19 PM, Bob Wilson <bob.wilson at apple.com>
>>>>>> wrote:
>>>>>> Author: bwilson
>>>>>> Date: Sat Nov  2 18:19:53 2013
>>>>>> New Revision: 193934
>>>>>> 
>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=193934&view=rev
>>>>>> Log:
>>>>>> Default to use libc++ on OS X 10.9+ and iOS 7+.
>>>>>> 
>>>>>> Modified:
>>>>>>   cfe/trunk/lib/Driver/ToolChains.cpp
>>>>>>   cfe/trunk/test/PCH/cxx-typeid.cpp
>>>>>> 
>>>>>> Modified: cfe/trunk/lib/Driver/ToolChains.cpp
>>>>>> URL:
>>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Driver/ToolChains.cpp?rev=193934&r1=193933&r2=193934&view=diff
>>>>>> 
>>>>>> ==============================================================================
>>>>>> --- cfe/trunk/lib/Driver/ToolChains.cpp (original)
>>>>>> +++ cfe/trunk/lib/Driver/ToolChains.cpp Sat Nov  2 18:19:53 2013
>>>>>> @@ -839,6 +839,12 @@ DerivedArgList *Darwin::TranslateArgs(co
>>>>>>    }
>>>>>>  }
>>>>>> 
>>>>>> +  // Default to use libc++ on OS X 10.9+ and iOS 7+.
>>>>>> +  if (((isTargetMacOS() && !isMacosxVersionLT(10, 9)) ||
>>>>>> +       (isTargetIPhoneOS() && !isIPhoneOSVersionLT(7, 0))) &&
>>>>>> +      !Args.getLastArg(options::OPT_stdlib_EQ))
>>>>>> +    DAL->AddJoinedArg(0, Opts.getOption(options::OPT_stdlib_EQ),
>>>>>> "libc++");
>>>>>> +
>>>>>>  // Validate the C++ standard library choice.
>>>>>>  CXXStdlibType Type = GetCXXStdlibType(*DAL);
>>>>>>  if (Type == ToolChain::CST_Libcxx) {
>>>>>> 
>>>>>> Modified: cfe/trunk/test/PCH/cxx-typeid.cpp
>>>>>> URL:
>>>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/PCH/cxx-typeid.cpp?rev=193934&r1=193933&r2=193934&view=diff
>>>>>> 
>>>>>> ==============================================================================
>>>>>> --- cfe/trunk/test/PCH/cxx-typeid.cpp (original)
>>>>>> +++ cfe/trunk/test/PCH/cxx-typeid.cpp Sat Nov  2 18:19:53 2013
>>>>>> @@ -1,8 +1,8 @@
>>>>>> // Test this without pch.
>>>>>> -// RUN: %clang_cc1 -include %S/cxx-typeid.h -fsyntax-only -verify %s
>>>>>> +// RUN: %clang_cc1 -include %S/cxx-typeid.h -fsyntax-only
>>>>>> -stdlib=libstdc++ -verify %s
>>>>>> 
>>>>>> -// RUN: %clang_cc1 -x c++-header -emit-pch -o %t.pch %S/cxx-typeid.h
>>>>>> -// RUN: %clang_cc1 -include-pch %t.pch -fsyntax-only -verify %s
>>>>>> +// RUN: %clang_cc1 -x c++-header -emit-pch -stdlib=libstdc++ -o
>>>>>> %t.pch %S/cxx-typeid.h
>>>>>> +// RUN: %clang_cc1 -include-pch %t.pch -fsyntax-only
>>>>>> -stdlib=libstdc++ -verify %s
>>>>>> 
>>>>>> // expected-no-diagnostics
>>>>>> 
>>>>>> 
>>>>>> 
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>>>>>> 
>>>>> 
>>>>> 
>>>> 
>>> 
>> 
>> 
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