Re: Zooming issues in interactive terminals

[Lutz M. <lut...@gm...>]

On Monday 19 May 2008 17:46:08 Ethan Merritt wrote:
> What compiler and glibc versions are you using?
> What hardware? You probably said before, but I've forgotten.

gcc 4.2.1 on x86-64, glibc 2.6.1 release 18.3 (openSUSE 10.3 packages)

> Does the man page for strtol on your system claim that it will
> set errno on overflow?

I think so:

     If the string has valid syntax for an integer but the value is not
     representable because of overflow, `strtol' returns either
     `LONG_MAX' or `LONG_MIN' (*note Range of Type::), as appropriate
     for the sign of the value.  It also sets `errno' to `ERANGE' to
     indicate there was overflow.

> I assume that you also get something else for the simpler test case:
>
> gnuplot> t = 313136844993
>              ^
>          warning: integer overflow; changing to floating point
> gnuplot> print t
> 313136844993.0

This is what I get:

gnuplot> t = 313136844993
gnuplot> print t
-395767615

I think the reason for this behavior is that the call to strtol does not 
generate an error, since the argument is within the range of a long 
integer, but then there is an implicit conversion to the smaller int type:

	token[t_num].l_val.v.int_val = strtol(str, &endptr, 0);

If I remember correctly, leading bits are simply truncated in a long->int 
conversion, and errno is not set.

Hope this helps,

  Lutz