Boost C++ Libraries: Ticket #7704: lexical_cast to filesystem::path fails for string::length > 22

component changed; owner set

Mon, 19 Nov 2012 18:33:52 GMT

owner set to Antony Polukhin
component None → lexical_cast

Antony Polukhin — Wed, 21 Nov 2012 13:58:27 GMT

Could not reproduce it on clang version 3.0-6ubuntu3 with default stl library.

It looks more like a libc++ bug, but I`m not sure.

Could you attach a backtrace? ( Have not found a .deb pakage for libc++ and don`t have enough time to install libc++ from sources)

Wed, 21 Nov 2012 14:57:58 GMT

That's consistent with what I've seen: I was not able to reproduce the problem when building without the -stdlib=libc++ flag. Unfortunately, the version of GNU libstdc++ available on Darwin is rather dated and thus not perceived as a path forward for new C++ development.

Here is a backtrace from the throw point:

#0  0x00007fff8457254d in __cxa_throw ()
#1  0x000000010000658c in boost::throw_exception<boost::bad_lexical_cast> (e=@0x7fff5fbff9a0) at throw_exception.hpp:66
#2  0x0000000100006249 in boost::detail::lexical_cast_do_cast<boost::filesystem::path, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::lexical_cast_impl (arg=@0x7fff5fbffaa0) at lexical_cast.hpp:2141
#3  0x0000000100005b7c in boost::lexical_cast<boost::filesystem::path, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > (arg=@0x7fff5fbffaa0) at lexical_cast.hpp:2300
#4  0x0000000100005162 in main () at lexical_cast_path.cpp:10

If you'd like me to try to get one from some other point in the code, let me know.

Antony Polukhin — Wed, 21 Nov 2012 21:17:44 GMT

Try this code:

#include <sstream>
#include <boost/filesystem/path.hpp>
int main()
{
    boost::filesystem::path p;
    std::istringstream s1("aaaaaaaaaaaaaaaaaaaaaaa");
    s1 >> p;
    if (s1.get() != std::char_traits<char>::eof())
        return EXIT_FAILURE;
    return 0;
}

If it exits with EXIT_FAILURE, then it is a bug in libc++

Wed, 21 Nov 2012 22:44:36 GMT

That test program succeeds (that is, it returns 0).

Antony Polukhin — Sat, 01 Dec 2012 18:45:32 GMT

Please, try this one:

#include <sstream>
#include <boost/filesystem/path.hpp>
#include <boost/lexical_cast.hpp>
template< class BufferType >
class stl_buf_unlocker: public BufferType{
public:
    typedef BufferType base_class;
    using base_class::pptr;
    using base_class::pbase;
    using base_class::setg;
    using base_class::setp;
};
typedef stl_buf_unlocker<std::basic_stringbuf<char> > unlocked_but_t;
int main()
{
    char data[] = "aaaaaaaaaaaaaaaaaaaaaaa";
    char* start = data;
    char* finish = start + sizeof(data);
    std::basic_istringstream<char> stream;
    static_cast<unlocked_but_t*>(stream.rdbuf())->setg(start, start, finish);
    stream.unsetf(std::ios::skipws);
    std::string output;
    // boost::filesystem::path output;
    const bool b1 = (stream >> output);
    const bool b2 = (stream.get() == std::char_traits<char>::eof());
    BOOST_ASSERT(b1);
    BOOST_ASSERT(b2);
    return 0;
}

If it does not trigger asserts, then comment std::string output; and uncomment boost::filesystem::path output; and try it once more.

Mon, 03 Dec 2012 16:42:07 GMT

In both cases no assert is triggered and the program returns 0.

Antony Polukhin — Sun, 24 Mar 2013 15:26:47 GMT

(In [83543]) Reimplement STL string buffer unlocker (refs #8267 and refs #7704)

Antony Polukhin — Sat, 30 Mar 2013 07:20:26 GMT

(In [83642]) Fix streams and buffers usage (refs #8267 and refs #7704). Now conversions the use STL streams shall work faster

Antony Polukhin — Sat, 30 Mar 2013 07:41:26 GMT

(In [83644]) Add tests for filesystem::path conversion (refs #7704)

status changed; resolution set

Antony Polukhin — Mon, 01 Apr 2013 20:40:46 GMT

status new → closed
resolution → fixed

(In [83689]) Merge from trunk:

Fix stream related issues with libc++ and clang (fixes #7704, fixes #8267)
Change runtime assert to compile time when converting to pointer (fixes #8334)

milestone changed

Antony Polukhin — Tue, 02 Apr 2013 06:51:18 GMT

milestone To Be Determined → Boost 1.54.0