https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118285
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
With minor tweaks to that:
--- pr118285-3.C 2025-01-28 16:30:15.798692471 +0100
+++ pr118285-5.C 2025-01-28 16:46:09.572904490 +0100
@@ -6,21 +6,21 @@ template <typename T> struct initializer
}
struct A {
char *a;
- union { char b[8]; long c; };
- constexpr A (const char *x) : a(b)
+ union U { char b[8]; long c; } u;
+ constexpr A (const char *x) : a(u.b)
{
for (int i = 0; i < 8; ++i)
- b[i] = 0;
+ u.b[i] = i;
}
constexpr ~A ()
{
if (!foo ())
- bar (c);
+ bar (u.c);
}
constexpr bool foo ()
{
char *x = a;
- if (x == b)
+ if (x == u.b)
return true;
return false;
}
so that it avoids using anonymous union just in case and initializes to nonzero
the b stuff, if I cxx_eval_constant_expression the whole *this in A::~A(), I
get
{.a=(char *) &D.2743.u.b, .u={.b={0, 1, 2, 3, 4, 5, 6, 7}}}
when evaluated as rvalue and
D.2730[0]
when evaluated as lvalue.
So this is about mismatch with what value the a member has been initialized, so
no wonder that foo () returns false.
