Re: [dev] [sic]: patches for string handling

On Wed, Sep 23, 2009 at 02:41:23PM +0100, Anselm R Garbe wrote:
>Hi,
>
>2009/9/23 Kris Maglione <maglione.k_AT_gmail.com>:
>> On Wed, Sep 23, 2009 at 12:53:35AM +0200, Mark Edgar wrote:
>>>
>>> * Fix buffer overrun when using strncpy()
>>
>> It's really sad to see code using strncpy.
>
>Well strncpy has performance issues on large buffers since it pads the
>remainder with null bytes. I agree that it would be better to use
>something else, though I don't like your util.c strlcpy solution
>because that's calling strncpy as well and does some superflous
>double-termination that seems to be unnecessary to me.

Unfortunately, the double-termination isn't superfluous because
strncpy doesn't always terminate. Just setting the buffer size 1
byte short doesn't help unless the last byte is already null. I
actually chose to use strncpy for LOC reasons, but memcpy isn't
much longer:

strlcpy(char *dest, char *src, int len) {
        int n;

        n = strlen(src);
        memcpy(dst, src, n < len ? n : len);
        if(len > 0)
                dst[len-1] = '\0';
}

I'd prefer:

strlcpy(char *dest, char *src, int len) {
        memcpy(dst, src, min(len, strlen(src)));
        dst[n-1] = '\0';
}

but then we'd need min.

>I applied both sic.c and util.c temporarily to sic/kris/, I need to
>sort out what I'm going to re-use and what not. The state when you
>patched sic.c seems to be quite old though... or your patch was quite
>big ;)

Yes, it's fairly old, I just didn't get the chance to sync it
with tip before I posted it since some of the changes are a bit
dramatic.

>Well apparently they push the line count to 296

Really?

%sloccount *.c
...
SLOC Directory SLOC-by-Language (Sorted)
252 top_dir ansic=252
...
Total Physical Source Lines of Code (SLOC) = 252

I shortened it to 251 because I #included util.c

It could actually be made quite a few lines shorter by, e.g.,
not automatically converting unknown commands to raw commands,
etc.

-- 
Kris Maglione
It is a miracle that curiosity survives formal education.
	--Albert Einstein