[Bug c++/87032] New: incorrect nested structure with union initialization

[vadim at sukhomlinov dot co]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87032

            Bug ID: 87032
           Summary: incorrect nested structure with union initialization
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vadim at sukhomlinov dot co
  Target Milestone: ---

For the code:
/**************/
struct f1 {int x,y;};
struct f2 {int x,y,z,t;};

struct T {
const char * name;
union {
       struct f1  fn1;
       struct f2  fn2;
} d;
};

extern "C" void p(struct T);

int main(){
p({"%x",{.fn2={1,2,3,4}}});
}
/******************/

gcc 7.3 generates:
<source>: In function 'int main()':

<source>:15:26: internal compiler error: in reshape_init_class, at
cp/decl.c:5802

 p({"%x",{.fn2={1,2,3,4}}});

                          ^

mmap: Invalid argument

gcc 8.1/8.2:
<source>: In function 'int main()':

<source>:15:26: error: could not convert '{"%x", {{1, 2, 3, 4}}}' from
'<brace-enclosed initializer list>' to 'T'

 p({"%x",{.fn2={1,2,3,4}}});

                          ^

Compiler returned: 1

At the same time Clang starting 3.1 and higher generates valid code.
Testing done using https://godbolt.org/