Using a pre-computed array in another function?

[Alasdair McAndrew]

Aargh - you're absolutely right!  I'm embarrassed to have made such an
elementary mistake: the variable A should be declared outside of main, thus
making it global, and initialized within main.

I'll go back under my rock now.

-Alasdair

On Mon, Jul 9, 2012 at 3:38 AM, Richard Damon <Richard at damon-family.org>wrote:

> On 7/8/12 12:38 AM, Alasdair McAndrew wrote:
> > Hi there,
> >
> > I have a pre-computed array, which I'd like to use in another function.
> >  This program shows the sort of thing I'm trying to do - I've created an
> > array A in the main program, and I need to use those values in my
> function
> > "mpz_myfun".  However, this gives me a segmentation fault.
> >
> > Any ideas as to how I can fix this up so it works?  Oh, I'm using gcc
> > version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3) and gmp 5.0.5.
> >
> > Thanks,
> > Alasdair
> >
> > #include <stdio.h>
> > #include <stdlib.h>
> > #include <gmp.h>
> >
> > mpz_t b,r,j,p,T,n,out;
> > mpz_t *A;
> >
> > void mpz_myfun(mpz_t r,mpz_t m)
> > {
> >   gmp_printf("Zd\n",A[100]);
> >   mpz_t tmp;
> >   mpz_init(tmp);
> >   mpz_and(tmp,m,T);
> >   mpz_set(r,A[mpz_get_ui(tmp)]);
> >   mpz_clear (tmp);
> > }
> >
> > int main(int argc, char *argv[])
> > {
> >    mpz_init_set_ui(b,7);
> >    mpz_init_set_ui(T,65535);
> >    mpz_init_set_ui(p,0x7FFFFFFF);
> >    mpz_init(j);
> >    mpz_t *A = malloc(65536*sizeof(mpz_t));
> >    for (unsigned long i=0; i<65536; i++)
> >      {
> >        mpz_powm_ui(A[i],b,i,p);
> >      }
> >
> >    mpz_init_set_str(n,argv[1],10);
> >    mpz_init(out);
> >
> >    mpz_myfun(out,n);
> >
> >    gmp_printf("%ZD\n",out);
> >
> >    return 0;
> > }
> > _______________________________________________
> > gmp-discuss mailing list
> > gmp-discuss at gmplib.org
> > https://gmplib.org/mailman/listinfo/gmp-discuss
> >
>
> You are declaring TWO different variables with the name A, one as a
> global, and one as a local in main, and it is the local that you are
> assigning the memory to, so myfun is seeing an A still at address 0.
>
> Change the line in main to just
>   A=malloc(65536(sizeof(mpz_t));
>
>
>
> --
> Richard Damon
>
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