Re: Re : "Pointer arithmetic using Null pointer in gawk-3.1.0 testsuite"

[Aharon Robbins]

> Date: Mon, 14 Apr 2003 20:36:34 -0700 (PDT)
> From: Olatunji Oluwabukunmi Ruwase <address@hidden>
> To: address@hidden
> Subject: Re : "Pointer arithmetic using Null pointer in gawk-3.1.0 testsuite"
>
> Hello,
>  I am working on a bounds checking patch to gcc.

This is good news.  Are you aware that Greg McGary did similar work?

>  While testing my patch on
> gawk-3.1.0 using the testsuite my compiler halts with an error message
> that indicating the attempt to use a null pointer in an arithmetic
> operation. In investigating the problem I ddecided to use only one of the
> test programs "basic" using the following command line
>
> address@hidden gawk-3.1.0]$ cd test
> address@hidden test]$ make basic
> io.c:2116:Bounds error: NULL or ILLEGAL pointer used in pointer
> arithmetic.
> io.c:2116:  Pointer value: NULL
> make: *** [addcomma] Error 134
>
> I verified this error message by modifying io.c (using the attached diff),
> and found out that the variable iop->buf is used in pointer arithmetic
> even when it is NULL. This situation exists even when compiling with the
> default gcc compiler.
> So I will like to find out if this is a bug or it is some deliberate non
> standard hack.
>
> Thank you
>
> tunji

The code's use was deliberate.  It works since the pointer that's derived
is never actually used in practice to dereference memory; just for a less
than comparison.

As Paul Eggert mentioned, that code is out of date. gawk 3.1.2 is the current
release, for which I rewrote the get_a_record() function (splitting it into
three separate ones).  I'd be interested to see your results on the current
code base.

Thanks,

Arnold