Re: GMP memory allocation and Macaulay2

[Doug Torrance <dtorrance@piedmont.edu>]

On 05/19/2016 03:59 PM, Bill Allombert wrote:
> On Thu, May 19, 2016 at 02:58:16PM -0400, Doug Torrance wrote:
> > Hello!
> >
> > Currently, PARI sets the GMP memory allocation functions in
> > pari_kernel_init().  However, this may cause problems for
> > applications which use both the PARI and GMP libraries such as
> > Macaulay2.  Building Macaulay2 against unpatched GMP and PARI
> > libraries causes segmentation faults.
> You issue is related to the bug #1317.
> Do you know why the segmentation faults occurs ? This is the
> crux of the matter.

I don't recall at the moment.  I'll work on getting back to you with a 
backtrace.

> > Currently, Macaulay2 builds its own GMP (actually MPIR, a drop-in
> > replacement) in which mp_set_memory_functions() does nothing.  This
> > is not ideal, however.  For example, this is the main problem
> > keeping Macaulay2 out of Debian, as it cannot be built with the
> > current Debian GMP and PARI packages.  (See [1] for some discussion
> > on this matter.)
> >
> > Would it be possible to remove the calls to
> > mp_set_memory_functions() from PARI?
> PARI only runs pari_kernel_init() once (in pari_init_opts),
> so you can just write a wrapper around pari_init() or pari_init_opts()
> that saves the values returned by mp_get_memory_functions() and resets
> them using mp_set_memory_functions() just after pari_init:
>
> void
> my_pari_init_opts(size_t parisize, ulong maxprime, ulong init_opts)
> {
>    void *(*new_gmp_malloc)(size_t new_size);
>    void *(*new_gmp_realloc)(void *ptr, size_t old_size, size_t new_size);
>    void (*new_gmp_free)(void *ptr, size_t old_size);
>    mp_get_memory_functions (&new_gmp_malloc, &new_gmp_realloc, &new_gmp_free);
>    pari_init_opts(parisize,maxprime,init_opts);
>    mp_set_memory_functions(new_gmp_malloc, new_gmp_realloc, new_gmp_free);
> }
>
> It is not possible to remove the call to mp_set_memory_functions() from
> the Debian packages in a reasonable timeframe.

Great suggestion -- thank you!  I'll try it out.