[PATCH][C++] Fix PR86763, wrong-code with TYPE_TYPELESS_STORAGE

[Szabolcs Nagy]

On 02/08/18 09:30, Richard Biener wrote:
> --- gcc/testsuite/g++.dg/torture/pr86763.C	(nonexistent)
> +++ gcc/testsuite/g++.dg/torture/pr86763.C	(working copy)
> @@ -0,0 +1,36 @@
> +// { dg-do run }
> +// { dg-additional-options "-fschedule-insns2 -fstrict-aliasing" }
> +
> +#include <cstdint>
> +#include <cassert>
> +#include <time.h>
> +struct ID {
> +  uint64_t value;
> +};
> +uint64_t value(ID id) { return id.value; }
> +uint64_t gen { 1000 };
> +struct Msg {
> +  uint64_t time;
> +  ID id;
> +};
> +struct V {
> +  V() { }
> +  V(Msg const & msg) : msg(msg) { }
> +  Msg & get() { return msg; }
> +  Msg msg;
> +  char pad[237 - sizeof(Msg)];
> +};
> +struct T : V { using V::V; };
> +Msg init_msg() {
> +  Msg msg;
> +  timespec t;
> +  clock_gettime(CLOCK_REALTIME, &t);

this fails on targets without clock_gettime (baremetal)
or targets that need -lrt at link time.

can we use something else here?
e.g. time(&t) works on baremetal and does not depend on -lrt.

> +  msg.time = t.tv_sec + t.tv_nsec;
> +  msg.id.value = ++gen;
> +  return msg;
> +}
> +int main() {
> +  T t;
> +  t = init_msg();
> +  assert(value(t.get().id) == 1001);
> +}
>