Why is there no std::stou?

Question

C++11 added some new string conversion functions:

http://en.cppreference.com/w/cpp/string/basic_string/stoul

It includes stoi (string to int), stol (string t

Answer 1

unsigned long ulval = std::stoul(buf);
unsigned long mask = ~0xffffffffl;
unsigned int uival;
if( (ulval & mask) == 0 )
    uival = (unsigned int)ulval;
else {
    ...range error...
}

Using masks to do this with the expected value size in bits expressed in the mask, will make this work for 64-bit longs vs 32-bit ints, but also for 32-bit longs vs 32-bit ints.

In the case of 64-bit longs, ~0xffffffffl will become 0xffffffff00000000 and will thus see if any of the top 32 bits are set. With 32-bit longs, it ~0xffffffffl becomes 0x00000000 and the mask check will always be zero.