Signal 6 coredump on lexical_cast with gcc option trapv

[Bernd Raum <braum@…>]

When compiling with g++ and option -ftrapv (trap overflow errors), a simple lexical_cast of a negative value causes a signal 6 dump:

boost::lexical_cast<long>(std::string("-3333"));

However, casting to double works fine.

We're currently using gcc 4.7.1 on a OpenSuse 12.1 platform.

[alexey kutumov <alexey.kutumov@…>]

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]

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

[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

[Antony Polukhin]

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]

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`
}

[Antony Polukhin]

More generic patch

[Antony Polukhin]

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

[Antony Polukhin]

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

[Antony Polukhin]

Fixed in [82268]

[Antony Polukhin]

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