Re: [Libguestfs] Note regarding bin2s.pl
On 12.01.2016 12:10, Richard W.M. Jones wrote:
On Tue, Jan 12, 2016 at 10:05:00AM +0000, Richard W.M. Jones wrote:
> On Tue, Jan 12, 2016 at 07:57:03AM +0100, Hilko Bengen wrote:
>> Helge,
>>
>> I have applied all the architecture-specific bits but not the bin2s
>> script yet. TBH, so far I don't see what is wrong about export and use
>> of the "_binary_init_size" constant.
>
> [https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=809185]
>
> I see it as a reasonable simplification - it allows us to get rid of
> that conditional code for HP-UX in bin2s.pl.
>
> However looking at the patch, I don't like the casts in:
>
> - size_t n = (size_t) &_binary_init_size;
> + size_t n = ((size_t) &_binary_init_end) - ((size_t) &_binary_init_start);
>
> Since those are pointers, it seems better to simply subtract them.
> (Though it would be better if we'd declared the type of
> _binary_init_start/_end as uint8_t instead of char.)
>
> If we must cast them then the correct integer to use is 'intptr_t', an
> int type that's guaranteed by C99 to be long enough to store a
> pointer.
How about the attached patch?
In general I'd say it looks OK.
Just a few comments:
-extern char _binary_init_start, _binary_init_end, _binary_init_size;
+extern uint8_t _binary_init_start, _binary_init_end;
Does the char to uint8_t change really makes such a big difference?
We will just use the address of the variable anyway.
- size_t n = (size_t) &_binary_init_size;
+ size_t n = &_binary_init_end - &_binary_init_start;
It's OK, but maybe some compilers/platforms might complain with a warning.
It might be better to keep a cast to (size_t), e.g.:
+ size_t n = (size_t) (&_binary_init_end - &_binary_init_start);
But either way, I'm fine with both approaches.
Thanks!
Helge