Re: [boost] [HEAD] lexical_cast<int8_t>("127") bug?

From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2007-05-07 12:01:40

Dean wrote:
> I've recently tried the following (inlined test) which isolates the
> problem I've encountered with boost::lexical_cast<int8_t>:
>
> #include <iostream>
> #include <boost/lexical_cast.hpp>
>
> int main(int argc, char * argv[]) {
>     int8_t value;
>     try {
>         value = boost::lexical_cast<int8_t>("127");
>     } catch (std::exception & e) {
>         std::cerr << e.what() << '\n';
>     }
>     return 0;
> };
>
> This is compiled with gcc 4.1.2 on Linux. Any idea why 127 wouldn't
> fit into an 8-bit signed integer? The defined range for signed 8 bit
> integers should be -127..+127 right?

Hi Dean,

You haven't said what you expected to happen and what happened 
instead.  So here's a guess: you expect int8_t to be treated as an 
integer by lexical_cast.  It isn't; despite the name, it's a character; 
you are asking it to convert a string to a character.  (Try some other 
strings where you have "127".  I think it will reject anything with 
more than one character in it.)

I have previously suggested that this behaviour should change, but the 
opinion of the list has been that using int8_t probably indicates 
"over-optimised code", and that the feature can be easily worked around 
with some additional casts.

In this case, I suggest that you lexical_cast to int, do a bounds check 
yourself (if necessary) and then assign to the int8_t.

Regards,

Phil.