[Lldb-commits] r151071 - in /lldb/trunk: examples/interposing/darwin/fd_interposing/FDInterposing.cpp include/lldb/lldb-defines.h source/Host/macosx/Host.mm source/Plugins/Process/Utility/UnwindMacOSXFrameBackchain.cpp tools/debugserver/source/MacOSX/MachThreadList.cpp tools/debugserver/source/MacOSX/i386/DNBArchImplI386.cpp tools/debugserver/source/MacOSX/x86_64/DNBArchImplX86_64.cpp

[Howard Hinnant]

> 
> On 21.02.2012, at 19:56, Greg Clayton wrote:
> 
>> Benjamin,
>> 
>> Please be careful when switching example code over to use C++11 as "lldb/trunk/examples/interposing/darwin/fd_interposing/FDInterposing.cpp" doesn't compile anymore. By default (in Lion at least) "std::shared_ptr" isn't part of the darwin libstdc++ library, so we still need to use the tr1 stuff.
>> 
>> I am checking without local C++ gurus on how to best fix this.
> 
> Oops, that was my mistake, checking that file in wasn't intended. I'll revert it.
> 
> This was just one little step to help switching to libc++ eventually. Sadly libc++ doesn't contain tr1 headers so we
> can't just flip the switch and everything works.

I'm going to start working on that faq real soon now! ;-)  Sorry it isn't there already.

The decision to not contain tr1 headers was a carefully considered one.  To do it right it would require a complete and separate tr1 implementation, and the manpower just wasn't there for that.

Fortunately there is an easy way to manage this transition that will auto-detect libc++, allowing your sources to switch back and forth between older std::libs and libc++ effortlessly.

Start with #include any C++03 header.  This is to get an identifying macro version number to tell which std::lib you're currently compiling with.  It could be <vector> or whatever you're previously using that is common to C++03 and C++11 libs.  If you're not already using such a header, don't include a big one gratuitously.  #include a small one gratuitously. ;-)

My favorite is:

#include <ciso646>  // Get std::lib version

The C++ committee was thoughtful enough to specify that this header does absolutely nothing! :-)  On libc++ it does almost nothing.  It will #define _LIBCPP_VERSION

Now your code knows what library you're compiling against, and there are a variety of techniques you can use to be compatible with libs that do or do not provide tr1/C++11:

#ifdef _LIBCPP_VERSION
// C++11
#  include <memory>   // for std::shared_ptr
#else
// TR1
#  include <tr1/memory>   // for std::tr1::shared_ptr
#endif

...

#ifdef _LIBCPP_VERSION
// C++11

typedef std::shared_ptr<FDEvent> FDEventSP;
typedef std::shared_ptr<String> StringSP;

#else
// TR1

typedef std::tr1::shared_ptr<FDEvent> FDEventSP;
typedef std::tr1::shared_ptr<String> StringSP;

#endif

Hope this helps.

Howard