Re: [boost] [Convert] std::isspace requires unsigned #28

Subject: Re: [boost] [Convert] std::isspace requires unsigned #28
From: Peter Dimov (lists_at_[hidden])
Date: 2017-03-20 11:13:10

Vladimir Batov wrote:
> On 2017-03-20 19:10, Olaf van der Spek via Boost wrote:
> >
> >> boost\convert\base.hpp(112): warning C6330: 'const char' passed as 
> >> _Param_(1) when 'unsigned char' is required in call to 'isspace'.
> >
> >> boost\convert\base.hpp(115): warning C6330: 'const char' passed as 
> >> _Param_(1) when 'unsigned char' is required in call to 'isspace'.
> >
> > https://github.com/boostorg/convert/issues/28
> >
> > IMO the code should be fixed and it's not a documentation issue.
> > What do you think?
>
> We discussed it on https://github.com/boostorg/convert/issues/28.

The analyzer is correct; passing char to isspace is a well-known bug, should 
be cast to unsigned char. The accepted range of the argument to isspace 
is -1..255 (assuming 8 bit character table), with -1 being EOF, and the 
default promotion from char to int doesn't do the right thing when char is 
signed.