Re: C bug of the day

[LLeweLLyn <llewelly.at@xmission.dot.com>]

Hyman Rosen <hyrosen@mail.com> writes:

> One of the trading systems we use in our company had been
> crashing every night for a week while trying to run a
> certain batch procedure. We finally traced the problem to
> the usual C bugaboo, a buffer overflow.
>
> In this case, the program was trying to form an SQL command
> for entering a row of data into a database table. Even though
> the program is written in C++,

I wonder if their implementation of C++ provides std::stringstream,
    whose use could have avoided this problem. I wonder if they had
    access to C99 snprintf, which at least provides a way to detect
    that the string was too long for the buffer, without out
    overriding the buffer.

Since you crossposted this to comp.lang.ada, I wonder if they had any
    programmers who knew there was a programming language named
    ada. :-) 

> the programmers apparently
> decided that the way to produce the SQL was to format it into
> a fixed-size buffer. Unfortunately, they decided to use '%f'
> to format some floating-point numbers, and more unfortunately,
> a situation arose in our data where a number was on the order
> of 10**141. Boom!
>
> We don't have the source code, but they do ship the program as
> relinkable libraries. We found the offending string and patched
> the binary to use %g instead of %f. Sigh.
[snip]

Now that is an *ugly* (but IMO necessary) solution ...

Perhaps you should raise the bug as justification for obtaining a
    source license.

I don't see that you have any point in posting this other than the
    obvious venting - I think we all have to do things like this once
    in a while.

However I would like to know of some ideas for dealing with this sort
    of thing. We all deal with reams of buggy and poorly designed
    code, but it seems most of the expert-recommended patterns and
    idioms assume good code.

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