Boost C++ Libraries: Ticket #7814: Signal 6 coredump on lexical_cast with gcc option trapv

status changed

Antony Polukhin — Thu, 20 Dec 2012 19:07:16 GMT

status new → assigned

attachment set

Sun, 23 Dec 2012 06:15:12 GMT

attachment → 7814.patch

Sun, 23 Dec 2012 06:20:21 GMT

The problem is in numeric_limits::min, because negating of minimum value of signed type is not representable as signed type (but representable as unsigned), so this line is incorrect:

utype const comp_val = static_cast<utype>(-(std::numeric_limits<Type>::min)());

Patch 7814.patch solves this problem

Antony Polukhin — Sun, 23 Dec 2012 08:08:54 GMT

That is not the only place where the problem occurs. There are several more places, where unary negation occurs, and they also need fixes (however they occur only when min/max value for a number is casted). Fast fixes did not help, because even some functions from std namespace trigger coredump.

I am afraid, that this issue won't be fixed in boost 1.53, but I'll try to find a good solution for the problem till 1.54

Sun, 23 Dec 2012 15:36:15 GMT

Replying to apolukhin:

Fast fixes did not help, because even some functions from std namespace trigger coredump.

Could you give example (related to lexical_cast) when coredump occurs

Antony Polukhin — Sun, 23 Dec 2012 15:38:46 GMT

I've added a patch, that fixes all the issues (even on clang, which is more strict in some cases). This patch is also fixes some warnings on VC++. I'll commit it after it passes all the tests on VC++ without a warning and fix for #7799 will be merged to release branch.

Antony Polukhin — Sun, 23 Dec 2012 15:50:56 GMT

Replying to alexey kutumov <alexey.kutumov@…>:

Replying to apolukhin:

Fast fixes did not help, because even some functions from std namespace trigger coredump.

Could you give example (related to lexical_cast) when coredump occurs

It was some code like:

template <class T>
void test_impl() {
    typedef std::numeric_limits<T> limits;
    boost::lexical_cast<std::string>((limits::min)());
    boost::lexical_cast<std::string>((limits::max)());
    // boost::lexical_cast<T>("lexical representation of limits::min or limits::max");
}
int main() {
    test_impl<int>();
    test_impl<unsigned int>();
    boost::lexical_cast<int>(0.0f); // Fails only on `clang -ftrapv`
}

attachment set

Antony Polukhin — Sun, 23 Dec 2012 20:50:44 GMT

attachment → lexical_cast.hpp.patch

More generic patch

severity changed; milestone deleted

Antony Polukhin — Sun, 23 Dec 2012 20:53:27 GMT

severity Problem → Regression
milestone To Be Determined

Updated patch with better one, fixed a bug with conversions of signed integers to unsigned integers

Antony Polukhin — Thu, 27 Dec 2012 20:17:11 GMT

(In [82227]) More strict tests, less workarounds, bugfixes (refs #7814)

status changed; resolution, milestone set

Antony Polukhin — Sat, 29 Dec 2012 14:43:59 GMT

status assigned → closed
resolution → fixed
milestone → Boost 1.53.0

Fixed in [82268]

Antony Polukhin — Sun, 03 Feb 2013 07:39:00 GMT

(In [82694]) More tests (refs #7814)