Re: gawk substr() problem

[Paul Eggert]

> From: Aharon Robbins <address@hidden>
> Date: Mon, 18 Nov 2002 15:31:13 +0200
> 
> --lint does catch the negative length case too:
> 
>       $ gawk --lint 'BEGIN{print substr("abc",2,-2)}'
>       gawk: cmd. line:1: warning: substr: length -2 is <= 0

Alas, --lint catches the zero length case as well; this is a bug,
since it's quite reasonable to compute a zero-length substring (e.g.,
when a match is zero length).  For example, gawk incorrectly issues a
diagnostic here:

  $ gawk --lint 'BEGIN {print substr("x", 1, 0);}' </dev/null
  gawk: cmd. line:1: warning: substr: length 0 is <= 0

Also, the diagnostics print the wrong number in many cases due to
floating-point versus integer anomalies.  E.g., on a 32-bit host::

  $ gawk --lint 'BEGIN {print substr("x", 1, 4294967294);}' </dev/null
  gawk: cmd. line:1: warning: substr: length -2 at start index 1 exceeds length 
of first argument (1)
  x
  $ gawk --lint 'BEGIN {print substr("x", 1, 1e300);}' </dev/null
  gawk: cmd. line:1: warning: substr: length -1 at start index 1 exceeds length 
of first argument (1)
  x
  $ gawk --lint 'BEGIN {print substr("x", 1, 1e300*1e300 - 1e300*1e300);}' 
</dev/null
  gawk: cmd. line:1: warning: substr: non-integer length NaN will be truncated
  gawk: cmd. line:1: warning: substr: length 2147483647 at start index 1 
exceeds length of first argument (1)
  x