Re: C PATCH for c/70093 (ICE with nested-function returning VM type)

[Jakub Jelinek <jakub at redhat dot com>]

On Wed, Mar 09, 2016 at 03:34:40PM +0100, Marek Polacek wrote:
> --- gcc/testsuite/gcc.dg/nested-func-10.c
> +++ gcc/testsuite/gcc.dg/nested-func-10.c
> @@ -0,0 +1,45 @@
> +/* PR c/70093 */
> +/* { dg-do compile } */
> +/* { dg-options "" } */
> +
> +void
> +foo (int n)
> +{
> +  struct S { int a[n]; };
> +
> +  struct S __attribute__((noreturn))
> +  fn (void)
> +  {
> +    struct S s;
> +    s.a[0] = 42;
> +    return s; /* { dg-warning "function declared .noreturn.|.noreturn. function does return" } */
> +  }
> +
> +  auto struct S __attribute__((noreturn))
> +  fn2 (void)
> +  {
> +    return fn (); /* { dg-warning "function declared .noreturn." } */
> +  }

Instead of the expecting warnings, wouldn't it be better to simply call
__builtin_abort () in fn ()?

> +  struct S x;
> +  x = fn ();
> +
> +  if (x.a[0] != 42)
> +    __builtin_abort ();
> +
> +  if (fn ().a[0] != 42)
> +    __builtin_abort ();
> +
> +  __typeof__ (fn ()) *p = &x;
> +  if (p->a[0] != 42)
> +    __builtin_abort ();
> +
> +  if (fn2 ().a[0] != 42)
> +    __builtin_abort ();

And do these all just conditionally, say in a big switch on foo's parameter?

And, I'm really surprised that you haven't included the case of a call
without lhs at the source level, so just
  fn ();
and
  fn2 ();
somewhere.

> --- gcc/testsuite/gcc.dg/nested-func-9.c
> +++ gcc/testsuite/gcc.dg/nested-func-9.c
> @@ -0,0 +1,45 @@
> +/* PR c/70093 */
> +/* { dg-do run } */
> +/* { dg-options "" } */
> +
> +void
> +foo (int n)
> +{
> +  struct S { int a[n]; };
> +
> +  struct S
> +  fn (void)
> +  {
> +    struct S s;
> +    s.a[0] = 42;
> +    return s;
> +  }
> +
> +  auto struct S
> +  fn2 (void)
> +  {
> +    return fn ();
> +  }
> +
> +  struct S x;
> +  x = fn ();
> +
> +  if (x.a[0] != 42)
> +    __builtin_abort ();
> +
> +  if (fn ().a[0] != 42)
> +    __builtin_abort ();
> +
> +  __typeof__ (fn ()) *p = &x;
> +  if (p->a[0] != 42)
> +    __builtin_abort ();
> +
> +  if (fn2 ().a[0] != 42)
> +    __builtin_abort ();

Similarly here, I miss calls that don't use the return value.

	Jakub