On Tue, Jan 12, 2016 at 06:21:14PM +0100, Helge Deller wrote: > 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.
It seems from this answer: https://stackoverflow.com/questions/2215445/are-there-machines-where-sizeofchar-1-or-at-least-char-bit-8 that sizeof (char) is always 1 so it would never make a difference. However I suppose it's better to be clearer about what we intend. > - 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); I tested the patch today on 32- and 64-bit Linux x86 systems, but nothing beyond that. Actually I think if it warns, I want to know about that -- eg. in some bizarre case where size_t isn't sufficient to store the result. Patch applied anyway, thanks. Rich. > But either way, I'm fine with both approaches. > > Thanks! > Helge -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/ _______________________________________________ Libguestfs mailing list [email protected] https://www.redhat.com/mailman/listinfo/libguestfs
