attachment set

Wed, 20 Feb 2013 08:17:24 GMT

attachment → test_lc.cpp

status changed; resolution set

Antony Polukhin — Sun, 24 Feb 2013 07:28:33 GMT

status new → closed
resolution → invalid

I'm afraid that this is not an error.

boost::lexical_cast has the behavior of std::stringstream, which uses num_get functions of std::locale to convert numbers. If we look at the Programming languages — C++, we'll see, that num_get uses the rules of scanf for conversions. And in the C99 standard for unsigned input value minus sign is optional, so if a negative number is read, no errors will arise and the result will be the two's complement.

I do not like such behaviour, but nothing can be done.

Some code to demonstrate that lexical_cast works exactly like std::stringstream

#include <boost/lexical_cast.hpp>
#include <sstream>
#include <assert.h>
int main() {
    std::stringstream ss("-1");
    unsigned int i;
    ss >> i;
    assert(boost::lexical_cast<unsigned int>("-1") == i);
}

Boost C++ Libraries: Ticket #8124: No more exception when casting from negative number string to unsigned

attachment set

status changed; resolution set