Segmentation fault with clang and libc++

[bobiko]

Hi all,

I am difficulties compiling a project with clang. This project also uses other framework which has its own dependencies, so it must be compiled with clang and linked against libc++ and libc++abi. The project compiles okay, but when I try to run it I get a segfault. Here is the traceback:

1  __cxxabiv1::__si_class_type_info::__do_dyncast(long, __cxxabiv1::__class_type_info::__sub_kind, __cxxabiv1::__class_type_info const *, void const *, __cxxabiv1::__class_type_info const *, void const *, __cxxabiv1::__class_type_info::__dyncast_result&) const               0x7f55964c89fb 
2  ??                                                                                                                                                                                                                                                                              0x7f55967e125e 
3  ??                                                                                                                                                                                                                                                                              0x7f55967e349e 
4  __gxx_personality_v0                                                                                                                                                                                                                                                            0x7f55967e3010 
5  _Unwind_RaiseException                                                                                                                                                                                                                                                          0x7f5595e8f96b 
6  __cxa_throw                                                                                                                                                                                                                                                                     0x7f55967e2a07 
7  std::__throw_ios_failure(const char *)                                                                                                                                                                                                                                          0x7f55964f8fe8 
8  std::basic_filebuf<char, std::char_traits<char>>::underflow()                                                                                                                                                                                                                   0x7f5596523a4a 
9  std::basic_istream<char, std::char_traits<char>>& std::getline<char, std::char_traits<char>, std::allocator<char>>(std::basic_istream<char, std::char_traits<char>>&, std::string&, char)                                                                                       0x7f55964e1079 
10 sofa::helper::Utils::readBasicIniFile(std::string const&)                                                                                                                                                                                                                       0x7f5595351d74 
11 sofa::helper::system::FileRepository::FileRepository(const char *, const char *, std::map<std::string, std::list<std::string>> const&)                                                                                                                                          0x7f55953b8d7b 
12 _GLOBAL__sub_I_FileRepository.cpp                                                                                                                                                                                                                                               0x7f55952d9c24 
13 call_init                                                                                                                                                                                                                                                         dl-init.c 72  0x7f55981af733 
14 _dl_init                                                                                                                                                                                                                                                          dl-init.c 119 0x7f55981af733 
15 _dl_start_user                                                                                                                                                                                                                                                                  0x7f55981a00ca 
16 ??                                                                                                                                                                                                                                                                              0x1            
17 ??                                                                                                                                                                                                                                                                              0x7ffebb3aa75a 
18 ??   

It seems that the problem arises when trying to init FileRepositories, but I am not really sure if it’s just a buggy library or something else. Have anyone encountered similar behaviour? I am using SOFA v19.12, Ubuntu 18 and clang 6.0

Best regards,
Vlad

[bobiko]

It seems that these difficulties are caused by initialization of DataRepository:

FileRepository DataRepository( "SOFA_DATA_PATH", 0, {
                                   { Utils::getSofaPathTo("etc/sofa.ini"), {"SHARE_DIR", "EXAMPLES_DIR"} }
                               });

When I change it to:

FileRepository DataRepository( "SOFA_DATA_PATH", ".");

Everything works without segfaults. It seems that the problem is related to the zero in char* argument, but I am not entirely sure to what it should be changed.

[Guillaume]

Hi,

Does the problem persist if you replace the 0 with nullptr?

[Hugo]

Hey @bobiko

Did Guillaume’s advice help?
Best

Hugo

[bobiko]

Hi @Hugo, Hi @Guillaume,

Sorry, I haven’t tried it yet, but I am pretty sure it will do the trick. Thanks a lot!

Best regards,
Vlad

[bobiko]

Hi @Hugo,

It’s been a while since I returned to this problem, but here is what I found. The bug arises from the fact that Utils::getSofaPathTo(const std::string& pathFromBuildDir) returns the path to the current dir if a file does not exist (including the situations when computeSofaPathPrefix() returns the current path):

const std::string Utils::getSofaPathTo(const std::string& pathFromBuildDir)
{
    std::string path = Utils::getSofaPathPrefix() + "/" + pathFromBuildDir;
    if(FileSystem::exists(path))
    {
        return path;
    }
    else
    {
        return Utils::getSofaPathPrefix();
    }
}

What happens then in the readBasicIniFile is that it receives the path to the current dir as the input, calls iniFile.good(), which returns success, and then tries to read from it (the directory, not a file), which is where an exception arises:

std::map<std::string, std::string> Utils::readBasicIniFile(const std::string& path)
{
    std::map<std::string, std::string> map;
    std::ifstream iniFile(path.c_str());
    if (!iniFile.good())
    {
        msg_error("Utils::readBasicIniFile()") << "Error while trying to read file (" << path << ")";
    }

    std::string line;
    while (std::getline(iniFile, line))
    {
        size_t equalPos = line.find_first_of('=');
        if (equalPos != std::string::npos)
        {
            const std::string key = line.substr(0, equalPos);
            const std::string value = line.substr(equalPos + 1, std::string::npos);
            map[key] = value;
        }
    }

    return map;
}

In my case, path is equal to /home/user/some-project-build-dir/. What I did to solve the problem was commenting out the following lines in Utils::getSofaPathTo():

const std::string Utils::getSofaPathTo(const std::string& pathFromBuildDir)
{
    std::string path = Utils::getSofaPathPrefix() + "/" + pathFromBuildDir;
    // if(FileSystem::exists(path))
    // {
        return path;
    // }
    // else
    // {
        // return Utils::getSofaPathPrefix();
    // }
}

Hope what I wrote makes sense to you 🙂

Best regards,
Vlad

[Hugo]

Hey @bobiko Vlad,

Thanks for your investigation.
Let me poke again @guillaumeparan

Best,

Hugo

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