How to enable C++11 in PNaCl?

[Alan Ide]

I have been reading through all the posts and have found that PNaCl should be able to compile "some" c++11 features. However when I add the following line to the Makefile:

CXXFLAGS:=-std=c++0x

The compiler still spits out:

/Developer/nacl_sdk/pepper_canary/toolchain/mac_x86_pnacl/newlib/usr/include/c++/4.6.2/bits/c++0x_warning.h:32:2: error: This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options.

Thoughts?

[Derek Schuff]

I believe that that particular warning is what you get when you include certain headers from c++11.

Currently PNaCl's C++ compiler is based on clang/llvm 3.3, which has pretty good C++11 support. however the C++ standard library is still based on gcc's libstdc++ 4.6, which is fairly old (and IIRC from before C++11 was officially standardized/named; hence the message referring to c++0x rather than c++11). For now you should be able to use C++11 language features (e.g. auto, range-based for), but until we update the standard library (which should be soon but probably not for the very first release), you'll get these warnings and C++11 features which require standard library support may or may not work.

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[Alan Ide]

Thanks for the info. I look forward to the future updates.

[Victor Khimenko]

On Wed, May 29, 2013 at 3:57 AM, Alan Ide <al...@digitalsynapses.com> wrote:

Thanks for the info. I look forward to the future updates.

I've took a look on this issue. libstdc++ 4.6 expects to see __GXX_EXPERIMENTAL_CXX0X__ defined but in GCC 4.7+ it was changed to check value of __cplusplus (it must be >= 201103L as standard requires). I think you should be able to use at least some features if you'll use "-std=c++0x -D__GXX_EXPERIMENTAL_CXX0X__=1" combination to fix this impedance. You will probably not be able to use features which need support in prebuilt library, but most STL-provided freatures are templates and thus will be inlined if you'll use -O2 switch.

[张华]

Use flag -std=gnu++11

[Derek Schuff]

What version of the SDK are you using? PNaCl hasn't used libstdc++ (which is the path you are seeing) in a long time. You can update to a recent SDK, or (depending on which version of the SDK you have) you can try the -stdlib=libc++ flag 

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