extract_uint IgnoreOverflowDigits=true problem at overflow

[Kojoley]

There is a bug either in extract_uint or real parser.

From my point of view the bug is in extract_uint because:

1. IgnoreOverflowDigits was added in the same commit as it usage in real parser 6832dc2
2. The 4294967296 either should result in 429496729 or 4294967290 but the iterator must be incremented.

#include <boost/spirit/include/qi.hpp>

namespace qi = boost::spirit::qi;

int main()
{
    {
        char const* s = "0.4294967296", *const e = s + std::strlen(s);
        std::cout << "=== float_ ===\n";
        std::cout << "input:    " << s << '\n';
        float f;
        if (qi::parse(s, e, qi::float_, f))
            std::cout << "result:   " << f << '\n'
                      << "expected: " << 0.4294967296f << '\n';
        else
            std::cout << "failed to parse\n";
    }
    {
        char const* s = "4294967296", *const e = s + std::strlen(s);
        std::cout << "=== extract_uint ===\n";
        std::cout << "input:    " << s << '\n';
        boost::uint32_t ul;
        boost::spirit::qi::extract_uint<boost::uint32_t, 10, 1, -1, false, true>::call(s, e, ul);
        std::cout << "result:   " << ul << '\n';
        std::cout << "at end:   " << std::boolalpha << (s == e) << '\n';
        std::cout << "chars left: " << (e - s) << '\n';
    }
}

Output:

=== float_ ===
input:    0.4294967296
result:   4.29497
expected: 0.429497
=== extract_uint ===
input:    4294967296
result:   4294967290
at end:   false
chars left: 1

https://wandbox.org/permlink/chIdPnbDOtS5FUat

[djowel]

That's a very bad bug! How did the tests not catch that :-( ? Do you have a fix?

[djowel]

Ah because IgnoreOverflowDigits is normally false (default) which the int parsers use.

[Kojoley]

Yes I have a fix Kojoley@3dc361a but I want to benchmark it before firing a PR.

[djowel]

Wonderful! Please add the test case.