Re: [PATCH v2 2/3] textconv: support for blame

> [resending to cc git@vger]
> 
> On Tue, Jun 15, 2010 at 12:29:43PM +0200, bonneta wrote:
> 
>> We have changed the declaration of textconv_object() to:
>> 
>> static int textconv_object(const char *path,
>>                            const unsigned char *sha1,
>>                            char **buf,
>>                            unsigned long *buf_size)
>> 
>> And now we can do:
>> *buf_size = fill_textconv(textconv, df, buf);
>> without any cast.
> 
> I assume you mean dropping the final buf_size parameter from that
> declaration, which is what your usage example has. I would return either
> an "unsigned long" or a size_t rather than an int. We are dealing with
> potential whole-file sizes, so it is better to use at least as large a
> data type as other parts of the code (we still may run into truncation
> problems, but at least you are not making things any worse).
> 
>> But we have to do:
>> textconv_object(read_from, null_sha1, &buf.buf, (unsigned long *)
>> &buf.len))
>> where buf.len is size_t.
>> 
>> Is that ok?
> 
> No, that has the same problem. Imagine a big endian machine with a
> 32-bit unsigned long and a 64-bit size_t. You would write into the first
> 32 bits of buf.len, which are the high bits, giving you a ridiculously
> large answer.
> 
> The only portable way in C to convert between types is by assignment. So
> you have to do:
> 
>   unsigned long foo;
>   textconv_object(read_from, null_sha1, &buf.buf, &foo);
>   buf.len = foo;
> 
> But now I'm confused. That matches the declaration you gave in the first
> part of your email, but not the usage example.