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// { dg-do compile { target c++20 } }
union U { int a; int b; int c[2]; };
constexpr int test1() {
U u;
u.a = 10;
*&u.b = 20; // { dg-error "accessing" }
return u.b;
}
constexpr int x1 = test1(); // { dg-message "in .constexpr. expansion" }
constexpr int test2() {
U u;
u.a = 10;
(0, u.b) = 20; // { dg-error "accessing" }
return u.b;
}
constexpr int x2 = test2(); // { dg-message "in .constexpr. expansion" }
constexpr int test3() {
U u;
u.a = 0;
int* p = &u.b;
p[u.a] = 10; // { dg-error "accessing" }
return u.b;
}
constexpr int x3 = test3(); // { dg-message "in .constexpr. expansion" }
constexpr int test4() {
U u;
u.a = 0;
int* p = &u.b;
u.a[p] = 10; // { dg-error "accessing" }
return u.b;
}
constexpr int x4 = test4(); // { dg-message "in .constexpr. expansion" }
struct S { U u[10]; };
constexpr int test5() {
S s;
s.u[4].a = 10;
6[s.u].b = 15;
return 4[s.u].a + s.u[6].b;
}
static_assert(test5() == 25);
constexpr int test6() {
U u;
u.a = 5;
u.c[0] = 3;
1[u.c] = 8;
return 1[u.c] + u.c[0];
}
static_assert(test6() == 11);
constexpr int test7() {
U u; // default initialisation leaves no member initialised
int* p = &u.a;
*p = 10; // { dg-error "accessing" }
return *p;
}
constexpr int x7 = test7(); // { dg-message "in .constexpr. expansion" }
constexpr int test8() {
U u {}; // value initialisation initialises first member
int* p = &u.a;
*p = 8;
return *p;
}
static_assert(test8() == 8);
union V { int :0; static int x; void foo(); int a; };
constexpr int test9() {
V v {}; // should skip zero-width bit fields, static members, and functions
int* p = &v.a;
*p = 9;
return *p;
}
static_assert(test9() == 9);
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