https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97038
Bug ID: 97038
Summary: [[no_unique_address]] support anonymous unions
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: no_unique_address at mail dot de
Target Milestone: ---
Compiling the following source file with g++ -std=c++20 -Wall -pedantic
--
struct A {};
struct B {};
struct C
{
[[no_unique_address]] union
{
[[no_unique_address]] A a;
[[no_unique_address]] B b;
} /*u*/;
char c;
};
static_assert(sizeof(C) == sizeof(char));
--
leads to the following output:
<source>:6:5: warning: attribute ignored in declaration of 'union C::<unnamed>'
[-Wattributes]
6 | {
| ^
<source>:6:5: note: attribute for 'union C::<unnamed>' must follow the 'union'
keyword
<source>:13:25: error: static assertion failed
13 | static_assert(sizeof(C) == sizeof(char));
| ~~~~~~~~~~^~~~~~~~~~~~~~~
Compiler returned: 1
See also: https://godbolt.org/z/GcW9cr
This works fine if the union is not anonymous.
This also works on clang 10.
It would be nice if it could be supported on gcc.
