FreeTDS Development Group

["Lowden, James K" <LowdenJK AT bernstein.com>]

> From: Thompson, Bill D (London) [mailto:ThompBil AT exchange.uk.ml.com]
> Sent: April 15, 2003 10:55 AM
> 
> No, free(NULL) does not cause me problems, I was just being careful.

That's good.  

> > tds_free_context(TDSCONTEXT *context)
> > {
> >         tds_free_locale(context->locale);
> >         TDS_ZERO_FREE(context);
> > }
> 
> Well no... if  context is NULL, you'll segment on referencing
> context->locale, so you need at least to check whether 
> context is NULL or not...

Oops! 

> so I guess you could simplify to....
> 
> void tds_free_context(TDSCONTEXT *context)
> {
>     if (context) {
>         tds_free_locale(context->locale);
>         context->locale = NULL;
>         TDS_ZERO_FREE(context);
>     }    
> }

That's effectively what's in CVS now.  

> if (g_dblib_ctx.tds_ctx) {
>      tds_free_context(g_dblib_ctx.tds_ctx);
>      g_dblib_ctx.tds_ctx = NULL;
> }
> 
> Although tds_free_context freed the storage pointed to by *context ,
> g_dblib_ctx.tds_ctx was still set, as the pointer had been 
> passed by value, not reference...

Come to think of it, 

>         context->locale = NULL;
>         TDS_ZERO_FREE(context);

is two degrees of silliness.  Not only is there no effect of
"context->locale = NULL", there's no effect the implicit "context = NULL"
either.  Whoever calls tds_free_context() won't see any changed value of
context, because, as you say, it's passed by value.  

We probably should avoid TDS_ZERO_FREE() in situations like this because
it's deceptive, and just use free() instead.  

Thanks for the patches, Bill.  Are you going to switch over to the newly
disturbed HEAD soon?  I know you're planning a lot of work on ct-lib, and I
wouldn't want us to get too far out of synch.  

--jkl


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