From: "Damian Yerrick" <web DOT poison AT pineight DOT 8m DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: problem with new malloc.c see note at bottom attn: Eli Zaretskii
Date: Fri, 24 Sep 1999 22:05:40 -0500
Organization: Rose-Hulman Institute of Technology
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References: <01JGCJLWUJ7A9I4LWV AT SLU DOT EDU> <20g103ddll DOT fsf AT Sky DOT inp DOT nsk DOT su>
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Michael Bukin <M DOT A DOT Bukin AT inp DOT nsk DOT su> wrote in message
news:20g103ddll DOT fsf AT Sky DOT inp DOT nsk DOT su...
> GAMMELJL AT SLU DOT EDU writes:
>
> > zvector w1;
> >
> > zvector operator+(zvector w8,zvector w9)
> > { int zi;
> >   for (zi=1;zi<length+1;zi++)
> >     {w1.s[zi+1]=w8.s[zi+1] + w9.s[zi+1];
> >     }
> >   return w1;
> > }
> >
> >    g=e+f;
>

> This assignment will use default assignment operator, which will copy
> all members from w1 to g.  Your class contains pointer to dynamically
> allocated memory, and after this assignment you have several classes
> which contain the same pointer, which is then deleted several times in
> destructors of those global objects (they are called before program
> terminates).  Freeing pointer twice may lead to crash, because free
> does not check whether pointer is valid.

Whenever you free() a block through a pointer, set the pointer to
NULL just to be safe.

I also see a fence post error. This code copies all elements from s[2] to
s[length + 1].
Remove the +1's and change zi's initial value to 0; then write back.

--
Damian Yerrick
http://pineight.webjump.com/