Re: [tip:x86/mm] x86, mm: Use a bitfield to mask nuisance get_user() warnings

["H. Peter Anvin" <hpa@zytor.com>]

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I just thought up this variant, I'm about to test it, but H.J., do you
see any problems with it?

#define itype(x) \
__typeof__(__builtin_choose_expr(sizeof(*(x)) > sizeof(0UL), 0ULL, 0UL))

I tried it out with a small test program (attached), and it seems to
work.  Next for using it in the kernel...

	-hpa


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#include <stdio.h>
#include <stdlib.h>

#define itype(x) __typeof__(__builtin_choose_expr(sizeof(*(x)) > sizeof(0UL), 0ULL, 0UL))

int main(void)
{
  const char *a;
  const short *b;
  const int *c;
  const long *d;
  const long long *e;
  const void **p;

  itype(a) aa;
  itype(b) bb;
  itype(c) cc;
  itype(d) dd;
  itype(e) ee;
  itype(p) pp;

  aa = 1;
  bb = 2;
  cc = 3;
  dd = 4;
  ee = 5;
  pp = 6;

  printf("a = %zu\n", sizeof(aa));
  printf("b = %zu\n", sizeof(bb));
  printf("c = %zu\n", sizeof(cc));
  printf("d = %zu\n", sizeof(dd));
  printf("e = %zu\n", sizeof(ee));
  printf("p = %zu\n", sizeof(pp));

  return 0;
}