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

[Nico Weber]

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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