[pacman-dev] Bug in libalpm: sizeof(off_t)

[Andrew Gregory]

On 11/25/13 at 09:08pm, Allan McRae wrote:
> On 22/11/13 22:37, Jeremy Heiner wrote:
> > On Thu, Nov 21, 2013 at 3:52 PM, Allan McRae <allan at archlinux.org> wrote:
> >> Nope - documenting is the only real way to deal with this.  For example:
> >>
> >> http://www.gnupg.org/documentation/manuals/gpgme/Largefile-Support-_0028LFS_0029.html
> > 
> > How about the approach outlined in the attachment? It passes 'make
> > check' and performs correctly when a libalpm client app goofs up.
> > 
> 
> Please send patches inline so we can easily comment.
> 
> I was quite surprised this worked:
> 
> +#define alpm_initialize(root,dbpath,err) \
> +  alpm_initialize_check_largefile(root, dbpath, err, sizeof(off_t))
> 
> The sizeof(off_t) gets evaluated before the #define?  That can't be
> right...   So must be optimised out?  I'm either missing something here
> or this is prone to breakage.

If I'm not mistaken, sizeof is evaluated at compile time.  This works
because the sizeof(off_t) in the #define is evaluated when the calling
program is compiled and the sizeof(off_t) inside
alpm_initialize_check_largefile is evaluated when alpm is compiled.

> I guess a working approach would be to find the size of off_t during
> configure (e.g. [1] - there are other approaches) and test sizeof(off_t)
> == SIZEOF_OFF_T  in alpm_initialise.

I don't see how this would work.  Because sizeof is a compile-time
operation, it *must* be provided by the program using alpm.

> Allan
> 
> [1]
> http://www.gnu.org/software/autoconf-archive/ax_compile_check_sizeof.html