[Bug fortran/68649] [6/7/8 Regression] note: code may be misoptimized unless -fno-strict-aliasing is used

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68649

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pault at gcc dot gnu.org

--- Comment #22 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---

What we _could_ do with our array descriptors is to cast them to
a pointer containing a flexible array member, i.e.

struct type_descr {
  type *base_addr;
  size_t offset;
  dtype_type dtype;
  index_type span;
  descriptor_dimension dim[];
}

which would make all our function calls equal.

I have lightly tested the concept with a C program, i.e.

foo.c:

struct Xflex { int n; int a[]; };

int foo (struct Xflex *f)
{
  int i;
  int s;
  s = 0;
  for (i=0; i<f->n; i++)
    s += f->a[i];

  return s;
}

bar.c:

#include <stdio.h>

struct Xflex { int n; int a[]; };
struct X2 { int n; int a[2]; };

struct X2 x;

int foo (struct Xflex *f);

int main(void)
{
  x.n = 2;
  x.a[0] = 1;
  x.a[1] = 3;
  printf("%d\n", foo((struct Xflex *) &x));
}

which seems to work.