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* [Bug c++/102013] New: Incorrect aggregate initialization of union
@ 2021-08-22 16:11 fchelnokov at gmail dot com
  2021-08-23  9:05 ` [Bug c++/102013] " rguenth at gcc dot gnu.org
  2021-08-23 23:06 ` pinskia at gcc dot gnu.org
  0 siblings, 2 replies; 3+ messages in thread
From: fchelnokov at gmail dot com @ 2021-08-22 16:11 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102013

            Bug ID: 102013
           Summary: Incorrect aggregate initialization of union
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

In this program:
```
#include <iostream>

struct A { int x = 1; };
struct B { int x = 0; };

union U {
    A a;
    B b;
};

int main() {
    U u{};
    std::cout << u.a.x;
}
```

GCC prints `0`: https://gcc.godbolt.org/z/8Tj4Y1Pv1
But the correct result is `1`, which is the default initializer of the first
union member `a` (see Clang 's result)

^ permalink raw reply	[flat|nested] 3+ messages in thread
* [Bug c++/102013] Incorrect aggregate initialization of union
  2021-08-22 16:11 [Bug c++/102013] New: Incorrect aggregate initialization of union fchelnokov at gmail dot com
@ 2021-08-23  9:05 ` rguenth at gcc dot gnu.org
  2021-08-23 23:06 ` pinskia at gcc dot gnu.org
  1 sibling, 0 replies; 3+ messages in thread
From: rguenth at gcc dot gnu.org @ 2021-08-23  9:05 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102013

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-08-23
           Keywords|                            |wrong-code
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC seems to consider U POD and simply emits

  <<cleanup_point   union U u = {};>>;

for the NSDMI

^ permalink raw reply	[flat|nested] 3+ messages in thread
* [Bug c++/102013] Incorrect aggregate initialization of union
  2021-08-22 16:11 [Bug c++/102013] New: Incorrect aggregate initialization of union fchelnokov at gmail dot com
  2021-08-23  9:05 ` [Bug c++/102013] " rguenth at gcc dot gnu.org
@ 2021-08-23 23:06 ` pinskia at gcc dot gnu.org
  1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-23 23:06 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102013

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This is interesting:
struct A { int x = 6; };
struct B { int x = 3; };
union U {
    A a;
    B b;
};
static_assert (U{}.a.x==6);
U a{};
int main() {
    if (a.a.x != 6)
      __builtin_abort();
}

The static_assert works ....

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-08-23 23:06 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-08-22 16:11 [Bug c++/102013] New: Incorrect aggregate initialization of union fchelnokov at gmail dot com
2021-08-23  9:05 ` [Bug c++/102013] " rguenth at gcc dot gnu.org
2021-08-23 23:06 ` pinskia at gcc dot gnu.org

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