Ticket #6975: lexical_cast.cpp

#include <iostream>
#include <boost/lexical_cast.hpp>

const unsigned short prec_mask = 0x0300;
const unsigned short prec_64   = 0x0300;
const unsigned short prec_53   = 0x0200;
const unsigned short prec_24   = 0x0100;

void print (const char* str, const double d)
{
    union { double dbl; void* ptr; } mix;
    mix.dbl = d;

    std::cout.precision(40);
    std::cout << str << "(" << mix.ptr << ") " << mix.dbl << "\n";
}

unsigned short get_fpu_control_word()
{
    unsigned short cw;
    __asm__ ("fnstcw %0" : "=m" (*&cw));

    std::cout << "CW: " << std::hex << cw << std::dec << "\n";
    return cw;
}

void reset_fpu_control_word (unsigned short prec)
{
    unsigned short cw = get_fpu_control_word();
    cw &= ~prec_mask;
    cw |= prec & prec_mask;
    __asm__ ("fldcw %0" : : "m" (*&cw));
    (void)get_fpu_control_word();
}

void convert_str (const char* ptr)
{
    const double d_cast = boost::lexical_cast<double>(ptr);
    const double d_atof = std::atof(ptr);

    std::istringstream strm(ptr);
    double d_strm(0.0); strm >> d_strm;

    std::cout << std::endl;
    std::cout << "str:                         " << ptr << "\n";

    if (d_cast != d_atof || d_cast != d_strm) std::cout << "DIFFERENT!\n";
    print ("boost::lexical_cast<double>: ", d_cast);
    print ("std::atof:                   ", d_atof);
    print ("std::istringstream:          ", d_strm);

    std::cout << std::endl;
}

int main()
{
    reset_fpu_control_word(prec_53);

    convert_str("-15352.00000000000");
    convert_str("153520000000000000000000");
    convert_str("1.535200000000000e+04");
    convert_str("4.932812500000000e+03");
    convert_str("4.932812500000000e+02");
    convert_str("4.932812500000000e+01");
    convert_str("49328125.00000000");
    convert_str("-1.600000000000001421");
    convert_str("-3.200000000000000178");
    return 0;
}