std::thread exception

[Stefan Kersten]

hi,

i'm in the process of porting a library to pnacl, starting with our unit tests, and came across a problem regarding std::thread in pepper_canary using libstdc++ 4.6.2. in the following code excerpt

#include <thread>

static void threadFunc()

{

    WARN("What?!");

}

TEST_CASE("Methcla/Utility/Semaphore/post", "Test post/wait.")

{

    try {

        std::thread thread(threadFunc);

        REQUIRE_NOTHROW(thread.join());

    } catch(std::runtime_error& e) {

        WARN(e.what());

        throw;

    }

}

the constructor of std::thread throws a std::runtime_error:

-------------------------------------------------------------------------------
Methcla/Utility/Semaphore/post
-------------------------------------------------------------------------------
tests/methcla_tests.cpp:102
...............................................................................

tests/methcla_tests.cpp:131: 
warning:
  Not owner

tests/methcla_tests.cpp:131: FAILED:
  {Unknown expression after the reported line}
due to unexpected exception with message:
  Not owner

the unit testing framework is hooked up to post to a div via javascript, which seems to work fine in other test cases. the same function utilizing the corresponding pthread functions works fine (code below). is there a known problem with std::thread in this version of pnacl/libstdc++? i tried using libc++ but then i ran into linker errors with ppapi_cpp which uses libstdc++. any pointers would be greatly appreciated!

thanks,

stefan

pthread example:

#include <pthread.h>

static void* threadFunc(void*)

{

    WARN("Yes!!!");

    return nullptr;

}

TEST_CASE("Methcla/Utility/Semaphore/post", "Test post/wait.")

{

    pthread_t thread;

    int err = pthread_create(&thread, nullptr, threadFunc, nullptr);

    REQUIRE(err == 0);

    REQUIRE(pthread_join(thread, nullptr) == 0);

}

[JF Bastien]

Hi Stefan,

I can indeed reproduce the problem. We're currently working to replace libstdc++ as the default to using libc++ instead, it's LLVM's usual C++ standard library and is much more recent and standard-compliant than libstdc++ 4.6.2. Could you give it a try by passing -stdlib=libc++ to the compiler? That worked locally for me. We could also fix the libstdc++ problem, but I'm afraid that when it comes to C++11 features that's one of many, updating to a newer version would probably be more sustainable. I expect libc++ to become the default in the next few days, and to hit canary soon after.

Let me know how that goes.

Thanks,

JF

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[JF Bastien]

yes, i've tried compiling with libc++, in fact that's the one i'd prefer since we're using it on all other target platforms, but i run into the following linker error when linking to ppapi_cpp:

Oh I see, sorry for the confusion!

 

i suppose i need a version of libppapi_cpp built with libc++ instead of libstdc++?

 Yes, until we switch the default standard library to libc++ you could either recompile your own libppapi_cpp.a with -stdlib=libc++, or you could hackishly include libppapi_cpp's *.cc files in your build. I'm sorry for the inconvenience, it should be fixed soon! Let me know if that works.

[Stefan Kersten]

hi jf,

On 3 Dec 2013, at 17:09, JF Bastien wrote:
> I can indeed reproduce the problem. We're currently working to replace libstdc++ as the default to using libc++ instead, it's LLVM's usual C++ standard library and is much more recent and standard-compliant than libstdc++ 4.6.2. Could you give it a try by passing -stdlib=libc++ to the compiler? That worked locally for me. We could also fix the libstdc++ problem, but I'm afraid that when it comes to C++11 features that's one of many, updating to a newer version would probably be more sustainable. I expect libc++ to become the default in the next few days, and to hit canary soon after.
>
> Let me know how that goes.

yes, i've tried compiling with libc++, in fact that's the one i'd prefer since we're using it on all other target platforms, but i run into the following linker error when linking to ppapi_cpp:

build/debug/pepper/llvm_ir/methcla-pnacl-tests_bc_obj/tests/methcla_tests.cpp.o: error: undefined reference to 'pp::Var::Var(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::_Rb_tree_decrement(std::_Rb_tree_node_base const*)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::_Rb_tree_rebalance_for_erase(std::_Rb_tree_node_base*, std::_Rb_tree_node_base&)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::_Rb_tree_decrement(std::_Rb_tree_node_base*)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(std::string const&)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::_Rb_tree_insert_and_rebalance(bool, std::_Rb_tree_node_base*, std::_Rb_tree_node_base*, std::_Rb_tree_node_base&)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::_Rb_tree_increment(std::_Rb_tree_node_base const*)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string()'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::string::compare(std::string const&) const'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::allocator<char>::allocator()'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::string::c_str() const'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::allocator<char>::~allocator()'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, std::allocator<char> const&)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::string::data() const'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::string::size() const'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::string::resize(unsigned int)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, unsigned int, std::allocator<char> const&)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string()'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::string::append(char const*)'
/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug/libppapi_cpp.a: error: undefined reference to 'std::string::length() const'

with the linker command line being:

/Users/skersten/dev/nacl_sdk/pepper_canary/toolchain/mac_pnacl/bin/pnacl-clang++ <OBJECTS> -stdlib=libc++ --pnacl-exceptions=sjlj -L/Users/skersten/dev/nacl_sdk/pepper_canary/lib/pnacl/Debug -lppapi_cpp -lppapi -lpthread -o build/debug/pepper/llvm_ir/methcla-pnacl-tests.bc

i suppose i need a version of libppapi_cpp built with libc++ instead of libstdc++?

thanks,
stefan

[Stefan Kersten]

On 3 Dec 2013, at 18:33, JF Bastien wrote:
> i suppose i need a version of libppapi_cpp built with libc++ instead of libstdc++?
>
> Yes, until we switch the default standard library to libc++ you could either recompile your own libppapi_cpp.a with -stdlib=libc++, or you could hackishly include libppapi_cpp's *.cc files in your build. I'm sorry for the inconvenience, it should be fixed soon! Let me know if that works.

ok, i've compiled libppapi_cpp with libc++ (NACL_CXXFLAGS doesn't seem to be honored by the Makefile btw):

make NACL_CXXFLAGS=-stdlib=libc++ NACL_CFLAGS=-stdlib=libc++ TOOLCHAIN=pnacl CONFIG=Debug V=1

now when linking against libppapi_cpp i get the following linker error related to the sjlj exception handling mechanism:

/Users/skersten/dev/nacl_sdk/pepper_canary/toolchain/mac_pnacl/lib/sjlj_eh_redirect.bc: error: undefined reference to '__pnacl_eh_sjlj_Unwind_RaiseException'
/Users/skersten/dev/nacl_sdk/pepper_canary/toolchain/mac_pnacl/lib/sjlj_eh_redirect.bc: error: undefined reference to '__pnacl_eh_sjlj_cxa_call_unexpected'
/Users/skersten/dev/nacl_sdk/pepper_canary/toolchain/mac_pnacl/lib/sjlj_eh_redirect.bc: error: undefined reference to '__pnacl_eh_sjlj_Unwind_Resume_or_Rethrow'
/Users/skersten/dev/nacl_sdk/pepper_canary/toolchain/mac_pnacl/lib/sjlj_eh_redirect.bc: error: undefined reference to '__pnacl_eh_sjlj_Unwind_DeleteException'

is there a straightforward fix for that? removing the use of exceptions from our library is not really an option ...

thanks again,
stefan

[Victor Khimenko]

Then PNaCl is not an option for you... right now. I guess you can star these bugs:

https://code.google.com/p/nativeclient/issues/detail?id=2798

https://code.google.com/p/nativeclient/issues/detail?id=3696

Slow (non-"zero cost") extensions must be added pretty soon (this is what second bug is all about), fast ones will be added later (ETA is not yet determined).

[Mark Seaborn]

I should be committing a change in the next couple of days to make SJLJ-based C++ exception handling work with libc++ in PNaCl.  It already works with libstdc++.  (The change is https://codereview.chromium.org/95613004/, if you want to follow its progress.)

Cheers,

Mark

[Stefan Kersten]

On 4 Dec 2013, at 21:56, Mark Seaborn wrote:
> I should be committing a change in the next couple of days to make SJLJ-based C++ exception handling work with libc++ in PNaCl. It already works with libstdc++. (The change is https://codereview.chromium.org/95613004/, if you want to follow its progress.)

thanks mark, that's good news! i'll wait for your commit then ....

stefan

[JF Bastien]

FYI libc++ should now be the default and SJLJ exception handling should work as expected (with the --pnacl-exceptions=sjlj flag) in the latest NaCl canary SDK.

[Stefan Kersten]

On 10 Dec 2013, at 19:48, JF Bastien wrote:
> FYI libc++ should now be the default and SJLJ exception handling should work as expected (with the --pnacl-exceptions=sjlj flag) in the latest NaCl canary SDK.

thanks for the update, our library now compiles fine!

stefan